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Date: 24 Sep 2004 00:40:36
From: W. Watson
Subject: Devices to Measure the Speed of Flowing Water?
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Is there a device or simple way to measure the speed of flowing water?
--
Wayne T. Watson (Watson Adventures, Prop., Nevada City, CA)
(121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time)
Obz Site: 39° 15' 7" N, 121° 2' 32" W
(Formerly Homo habilis, erectus, heidelbergensis and now sapiens)
"The meek are ready." -- Anon
Web Page: <home.earthlink.net/~mtnviews >
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Date: 28 Sep 2004 09:04:39
From: Scott M. Knowles
Subject: Re: Devices to Measure the Speed of Flowing Water?
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> "W. Watson" <wolf_tracks@invalid.inv> wrote in message news:<82K4d.1491$zG1.928@newsread3.news.pas.earthlink.net>...
> I take it you haven't used a GPS very much since the elimination of SA
> four years ago. I use mine almost daily while walking and it shows my
> usual 2.5 mph speed very well and correctly goes up to 3 or 3.5 if I
> speed up a little. There is a noticeable time lag of a couple seconds
> since it does a little averaging, but when moving steadily with
> reasonable reception the displayed speed is accurate to about 0.1-0.2
> mph. At the typical 3 - 4 mph speed of a river plus paddling speed
> this gives your speed with only a small percentage error. I find it
> most useful when seakayaking in areas with significant tides to be able
> to check what my actual rate of progress is (or the tide speed if I drift).
> BTW, GPS receivers do not depend on just positional changes to determine
> velocities. They also measure the Doppler frequency shift of the
> satellite signals.
That's cool and you're right, I haven't looked at them in a few years.
Questions. Even with SA off, what's the position error? I
understood it's at best 3 meters, often 4-6+ meters, and worse with
fewer satellites. If that's the case I don't see if measuring flow
over short intervals accurately. Or I'm missing something.
How often do you check your position and average velocity? Are these
in basic models GPS's or more advanced ones?
It would be interesting to check it in realtime for continues velocity
computations. It would give you the average over the line you go,
which means maintaining a line along the direction of the flow so the
value isn't representing a wandering line or with any paddling
included. And it won't give you the average at a point but along that
line (reach). I'm not sure I'd want to check in fast(er) flows.
Thanks.
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Date: 29 Sep 2004 00:36:06
From: John R Weiss
Subject: Re: Devices to Measure the Speed of Flowing Water?
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"Scott M. Knowles" <scott@wsrphoto.com > wrote...
>
> That's cool and you're right, I haven't looked at them in a few years.
> Questions. Even with SA off, what's the position error? I
> understood it's at best 3 meters, often 4-6+ meters, and worse with
> fewer satellites. If that's the case I don't see if measuring flow
> over short intervals accurately. Or I'm missing something.
A good discussion is at http://www.cast.uark.edu/cast/bruce_gps/GPS_Week4.ppt.
Errors vary with time, and vertical position error is somewhat greater than
horizontal position error. RMS horizontal position error is on the order of
2-2.5 meters. The author of the presentation describes the RMS error as a 95%
probability, based on a 95% confidence interval, that the position will be
within the stated distance. At http://members.shaw.ca/pdops/WAAS.html you can
see a sample of a WAAS-enabled GPS that shows horizontal position errors from
benchmarks ranging from 0.0 to 2.2 meters.
> How often do you check your position and average velocity? Are these
> in basic models GPS's or more advanced ones?
If the GPS has a map (either a built-in "base map" or higher-resolution area map
loaded from CD), position is constantly displayed. You can monitor lat/long as
well, and see whether it's wandering while you're stationary. Even basic
handheld GPS units can display average speed (since the last time the log was
reset) as well as current speed.
> It would be interesting to check it in realtime for continues velocity
> computations. It would give you the average over the line you go,
> which means maintaining a line along the direction of the flow so the
> value isn't representing a wandering line or with any paddling
> included. And it won't give you the average at a point but along that
> line (reach). I'm not sure I'd want to check in fast(er) flows.
I've brought my GPS on my kayak many times. Velocities are very consistent when
paddling a relatively straight course, and changes can be seen quite easily.
When accelerating and/or turning, the update rate of the unit (mine has 2
selectable rates; the higher rate uses batteries much faster) makes a big
difference. I see good, consistent results with the high update rate (5/sec).
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Date: 28 Sep 2004 18:14:58
From: Peter
Subject: Re: Devices to Measure the Speed of Flowing Water?
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John R Weiss wrote:
> I've brought my GPS on my kayak many times. Velocities are very consistent when
> paddling a relatively straight course, and changes can be seen quite easily.
> When accelerating and/or turning, the update rate of the unit (mine has 2
> selectable rates; the higher rate uses batteries much faster) makes a big
> difference. I see good, consistent results with the high update rate (5/sec).
Yes, I use mine when kayaking as well and the velocity readings appear
very reasonable and consistent. But I'm wondering what make/model you
have that updates 5 times a second. The ones I've seen that have
faster than once/second updates have also had very high price tags
and weren't really designed for activities like kayaking.
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Date: 29 Sep 2004 01:58:43
From: John R Weiss
Subject: Re: Devices to Measure the Speed of Flowing Water?
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"Peter" <prathman@comcast.net > wrote...
>
> But I'm wondering what make/model you
> have that updates 5 times a second. The ones I've seen that have
> faster than once/second updates have also had very high price tags
> and weren't really designed for activities like kayaking.
Garmin GPS 3+. "Battery saver" mode is 1/sec update; turn that off for 5/sec.
Waterproof. Has been rained on and sprayed with salt water many times. Still
works.
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Date: 28 Sep 2004 19:17:54
From: Peter
Subject: Re: Devices to Measure the Speed of Flowing Water?
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John R Weiss wrote:
> "Peter" <prathman@comcast.net> wrote...
>
>> But I'm wondering what make/model you
>>have that updates 5 times a second. The ones I've seen that have
>>faster than once/second updates have also had very high price tags
>>and weren't really designed for activities like kayaking.
>
>
> Garmin GPS 3+. "Battery saver" mode is 1/sec update; turn that off for 5/sec.
Better check that. All Garmins that I've seen, including my III+, only
update once per second in "Normal" mode. "Battery Saver" mode reduces
that to once every 5 seconds provided your previous movement was fairly
predictable.
>
> Waterproof. Has been rained on and sprayed with salt water many times. Still
> works.
The unit itself is rated to IPX7 for waterproofness, which corresponds
to immersion in still water at a depth of 1 m for 30 seconds. However
Garmin does not certify that the battery compartment is waterproof and
saltwater in there could quickly corrode the contacts, so it's generally
still best to protect the unit in a clear waterproof pouch.
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Date: 29 Sep 2004 03:41:25
From: John R Weiss
Subject: Re: Devices to Measure the Speed of Flowing Water?
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"Peter" <prathman@comcast.net > wrote...
>
> Better check that. All Garmins that I've seen, including my III+, only
> update once per second in "Normal" mode. "Battery Saver" mode reduces
> that to once every 5 seconds provided your previous movement was fairly
> predictable.
OK. I'll check the book again. It's been 3 or 4 years since I read it.
> Garmin does not certify that the battery compartment is waterproof and
> saltwater in there could quickly corrode the contacts, so it's generally
> still best to protect the unit in a clear waterproof pouch.
I do when kayaking, but not generally when on the sailboat.
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Date: 29 Sep 2004 19:06:31
From: Michael Daly
Subject: Re: Devices to Measure the Speed of Flowing Water?
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On 28--2004, "John R Weiss" <jrweiss98155@.comNOSPAMcast.net > wrote:
> > Better check that. All Garmins that I've seen, including my III+, only
> > update once per second in "Normal" mode. "Battery Saver" mode reduces
> > that to once every 5 seconds provided your previous movement was fairly
> > predictable.
>
> OK. I'll check the book again. It's been 3 or 4 years since I read it.
<http://www.garmin.com/products/gpsIIIp/spec.html > agrees with Peter.
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Date: 28 Sep 2004 09:20:16
From: Peter
Subject: Re: Devices to Measure the Speed of Flowing Water?
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Scott M. Knowles wrote:
>>I take it you haven't used a GPS very much since the elimination of SA
>>four years ago. I use mine almost daily while walking and it shows my
>>usual 2.5 mph speed very well and correctly goes up to 3 or 3.5 if I
>>speed up a little. There is a noticeable time lag of a couple seconds
>>since it does a little averaging, but when moving steadily with
>>reasonable reception the displayed speed is accurate to about 0.1-0.2
>>mph. At the typical 3 - 4 mph speed of a river plus paddling speed
>>this gives your speed with only a small percentage error. I find it
>>most useful when seakayaking in areas with significant tides to be able
>>to check what my actual rate of progress is (or the tide speed if I drift).
>>BTW, GPS receivers do not depend on just positional changes to determine
>>velocities. They also measure the Doppler frequency shift of the
>>satellite signals.
>
>
> That's cool and you're right, I haven't looked at them in a few years.
> Questions. Even with SA off, what's the position error? I
> understood it's at best 3 meters, often 4-6+ meters, and worse with
> fewer satellites.
Without some form of DGPS about 7 meters, with WAAS or other type of
DGPS it's around 2 meters.
> If that's the case I don't see if measuring flow
> over short intervals accurately. Or I'm missing something.
As mentioned above the receivers also measure the Doppler shift and
get the velocity relative to the satellites directly that way.
And much of the error is from slowly-varying sources, such as the
effective index of refraction of the troposphere. The reported
position can still fluctuate quickly if the satellites being
used for the calculation change, but the pseudo-range-rate (relative
velocity) to a given satellite is much more stable. The algorithms
used to smooth the data and combine the information from positional
and velocity measurements are proprietary to each manufacturer, but
there's much more to it than simply (pos.1 - pos.2)/t.
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Date: 28 Sep 2004 17:20:40
From: Michael Daly
Subject: Re: Devices to Measure the Speed of Flowing Water?
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On 28--2004, Peter <prathman@comcast.net > wrote:
> Without some form of DGPS about 7 meters, with WAAS or other type of
> DGPS it's around 2 meters.
With SA it is 100m, 95% of the time. Without SA, it's 15m, 95% of the
time. That means that 5% of the time, the error is larger.
BTW - lots of modern GPS units use WAAS, so the errors are considerably
smaller. Mine is a very old model and doesn't, so I always assume no
WAAS. This means that my GPS will show larger errors in position and
speed/direction most of the time. I should have been more clear.
If your unit doesn't have or isn't using WAAS, watch out for errors.
Otherwise, the errors will only be significant for very small speeds.
Mea culpa.
Mike
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Date: 28 Sep 2004 10:20:15
From: Peter
Subject: Re: Devices to Measure the Speed of Flowing Water?
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Michael Daly wrote:
> On 28--2004, Peter <prathman@comcast.net> wrote:
>
>
>>Without some form of DGPS about 7 meters, with WAAS or other type of
>>DGPS it's around 2 meters.
>
>
> With SA it is 100m, 95% of the time.
Selective Availability was turned down to 0 in May of 2000 and there
have been no indications that it will ever be turned back on so
the 100 m number is only of historical interest.
> Without SA, it's 15m, 95% of the
> time. That means that 5% of the time, the error is larger.
Also based on old and very conservative estimates. Actual measurements
at accurately surveyed marks have shown the performance to be within
about 7 meters 95% of the time based on reports by several individuals
each collecting many thousands of data points.
>
> BTW - lots of modern GPS units use WAAS, so the errors are considerably
> smaller. Mine is a very old model and doesn't, so I always assume no
> WAAS. This means that my GPS will show larger errors in position and
> speed/direction most of the time. I should have been more clear.
> If your unit doesn't have or isn't using WAAS, watch out for errors.
> Otherwise, the errors will only be significant for very small speeds.
WAAS isn't all that reliable in most of the US since it depends on
having a line-of-sight to one of the two geostationary satellites
that broadcast the correction data. Since they are geostationary,
they're located over the equator and appear fairly far south in the
sky where they can easily be blocked by thick foliage.
However, even without WAAS corrections the speed errors are generally
within .1 - .2 knots which stil gives reasonable accuracy for most
paddling applications.
> Mea culpa.
>
> Mike
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Date: 28 Sep 2004 18:00:27
From: William R. Watt
Subject: Re: Devices to Measure the Speed of Flowing Water?
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Peter (prathman@comcast.net) writes:
> WAAS isn't all that reliable in most of the US since it depends on
> having a line-of-sight to one of the two geostationary satellites
> that broadcast the correction data. Since they are geostationary,
> they're located over the equator and appear fairly far south in the
> sky where they can easily be blocked by thick foliage.
sounds like they would be most useful during the summer paddling season. :)
--
--------------------
William R Watt National Capital FreeNet Ottawa's free community network
homepage: www.ncf.ca/~ag384/top.htm
warning: non-FreeNet email must have "notspam" in subject or it's returned
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Date: 28 Sep 2004 05:03:49
From: Scott M. Knowles
Subject: Re: Devices to Measure the Speed of Flowing Water?
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"W. Watson" <wolf_tracks@invalid.inv > wrote in message news:<82K4d.1491$zG1.928@newsread3.news.pas.earthlink.net>...
> Is there a device or simple way to measure the speed of flowing water?
Interesting discussion, but GPS, even precision GPS, won't work. The
error in the GPS is far greater than the velocities you'll find. Most
rivers flow between 1 and 6 feet per second, generally only exceeding
during high flows, or near or through channel constrictions. If all
you want it is the velocity in a river reach, you can use yourself
(kayak) as floating debris, just time yourself without paddling
through a reach, eg. 50-100 feet. But I haven't seen what you want to
know.
--Scott--
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Date: 28 Sep 2004 23:34:52
From: John R Weiss
Subject: Re: Devices to Measure the Speed of Flowing Water?
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"Scott M. Knowles" <scott@wsrphoto.com > wrote...
>
> Interesting discussion, but GPS, even precision GPS, won't work. The
> error in the GPS is far greater than the velocities you'll find. Most
> rivers flow between 1 and 6 feet per second, generally only exceeding
> during high flows, or near or through channel constrictions. If all
> you want it is the velocity in a river reach, you can use yourself
> (kayak) as floating debris, just time yourself without paddling
> through a reach, eg. 50-100 feet. But I haven't seen what you want to
> know.
Modern consumer-grade GPS receivers provide velocities accurate to within 0.1
knot (0.17 feet/second). Depending on the specific receiver type, update rate,
and display, a reasonably accurate velocity can be obtained. OTOH, I have seen
few rivers (maybe none) that have calibrated distance markers over any
significant reach, so timing over a measured reach, with its required subsequent
calculations, is not a viable option most of the time.
The OP did not specify the required precision or scope (e.g., surface or
specific depth, size of sample area, etc) of the speed he wants to measure.
Since "the speed of flowing water" varies greatly on any section of a river, and
varies with depth even at a specific position, its valid measurement depends on
the purpose of the measurement. Until he gives us more specifics, the
discussion of GPS-provided velocities to measure the speed of the river flow at
the surface is relevant and applicable to the purpose.
GPS will provide a reasonably accurate velocity (+/- 0.1 knots or so) over a
relatively short distance (dependent on velocity) and time (1-2 seconds or
less). With a GPS receiver mounted in a kayak or canoe or other paddle boat,
the average speed of the flowing water at/near the surface can be determined
over a relatively short reach. Effects of wind and acceleration of the water
have to be taken into account, but again we do not have the scope of the problem
to determine whether these factors will prevent measurement to the desired
accuracy.
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Date: 29 Sep 2004 19:36:52
From: Michael Daly
Subject: Re: Devices to Measure the Speed of Flowing Water?
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On 28--2004, "John R Weiss" <jrweiss98155@.comNOSPAMcast.net > wrote:
> Modern consumer-grade GPS receivers provide velocities accurate to within 0.1
> knot
Leave your GPS sitting in one spot and watch the velocity change. You'll
see velocities much larger than 0.1 kt. I'm not talking about specs here,
I'm talking about turning the unit on and watching what happens.
Mike
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Date: 30 Sep 2004 00:11:03
From: John R Weiss
Subject: Re: Devices to Measure the Speed of Flowing Water?
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"Michael Daly" <michaelDaly@foo.bar > wrote:
>
>> Modern consumer-grade GPS receivers provide velocities accurate to within 0.1
>> knot
>
> Leave your GPS sitting in one spot and watch the velocity change. You'll
> see velocities much larger than 0.1 kt. I'm not talking about specs here,
> I'm talking about turning the unit on and watching what happens.
OK...
Garmin GPS 3+, no WAAS or DGPS.
Inside, at the desk: 3 sats, DOP 5.8. Distance from a nearby waypoint
initialized at 76' and varied from 68 to 82 over 5 minutes. Distance stayed
between 70 and 75 most of the time. Velocity never came off 0.0.
Outside on patio: 6 sats, DOP 2.1. Distance initialized at 74' and varied
from 67 to 77; most of the time between 70 and 73. Velocity always 0.0.
Walking up and down the street over a span of less than 200' the velocity
started reading after 11 steps and steadied at 3.4 - 3.5 mph. Speed varied
proportionate to my slowing, turning, etc. Since I have previously measured my
brisk walking pace at 17-19 minutes per mile, the GPS results are consistent.
Looks accurate enough to me to me...
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Date: 29 Sep 2004 14:39:01
From: Peter
Subject: Re: Devices to Measure the Speed of Flowing Water?
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Michael Daly wrote:
> On 28--2004, "John R Weiss" <jrweiss98155@.comNOSPAMcast.net> wrote:
>
>
>>Modern consumer-grade GPS receivers provide velocities accurate to within 0.1
>>knot
>
>
> Leave your GPS sitting in one spot and watch the velocity change.
It gets pretty boring watching the display that just says 0.0 knots
for long periods of time with a few sporadic blips up to a few tenths.
And when walking at a steady pace the displayed speed is also almost
always constant within 0.1 or 0.2 mph.
> You'll
> see velocities much larger than 0.1 kt.
Some, which is not surprising since the spec is for 95% of the readings,
so once every 20 seconds or so one might expect a reading that's higher
than the spec.
> I'm not talking about specs here,
> I'm talking about turning the unit on and watching what happens.
When I've connected mine to my PC and recorded the readings over
extended periods of time the results have been in agreement with
the specifications.
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Date: 30 Sep 2004 04:31:24
From: Michael Daly
Subject: Re: Devices to Measure the Speed of Flowing Water?
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On 29--2004, Peter <prathman@comcast.net > wrote:
> > Leave your GPS sitting in one spot and watch the velocity change.
>
> It gets pretty boring watching the display that just says 0.0 knots
> for long periods of time with a few sporadic blips up to a few tenths
And I've seen mine wander around 3-7 kph for a while before settling down
to a smaller number lots of times. YMMV. Garmin 12XL.
> Some, which is not surprising since the spec is for 95% of the readings,
> so once every 20 seconds or so one might expect a reading that's higher
> than the spec.
Not random, consistent. Again - YMMV.
It's funny, ever since they turned off SA, so many people claim their
GPS readings are perfectly accurate. Turning off SA only increased the
accuracy by a factor of 6.
> When I've connected mine to my PC and recorded the readings over
> extended periods of time the results have been in agreement with
> the specifications.
Of course - averaging kicks in. Duh...
Mike
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Date: 29 Sep 2004 22:23:38
From: Peter
Subject: Re: Devices to Measure the Speed of Flowing Water?
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Michael Daly wrote:
> On 29--2004, Peter <prathman@comcast.net> wrote:
>
>
>>>Leave your GPS sitting in one spot and watch the velocity change.
>>
>>It gets pretty boring watching the display that just says 0.0 knots
>>for long periods of time with a few sporadic blips up to a few tenths
>
>
> And I've seen mine wander around 3-7 kph for a while before settling down
> to a smaller number lots of times. YMMV. Garmin 12XL.
It would be nice to have some reasonable statistics to see how
significant your "many" times are. When I've recorded data from
my GPS receivers over thousands of samples such outliers occur
only a few percent (and usually under 1%) of the time and are
pretty obvious and easily discarded in practice.
The existence of such occasional outliers is recognized in the
accuracy specifications being given as holding for 95% or more
of the samples.
Another thing to note is that the 12XL is a pretty old design
which was introduced in 1997 when expectations were that
SA was going to be with us for the foreseeable future.
As a result, I wouldn't be at all surprised if the firmware
design wasn't quite as concerned with avoiding such small
'glitches' given that the effects of SA would frequently
produce them anyway. But my experience with the Garmin 12
is still that such outlier values are rather rare.
>
>
>>Some, which is not surprising since the spec is for 95% of the readings,
>>so once every 20 seconds or so one might expect a reading that's higher
>>than the spec.
>
>
> Not random, consistent. Again - YMMV.
>
> It's funny, ever since they turned off SA, so many people claim their
> GPS readings are perfectly accurate. Turning off SA only increased the
> accuracy by a factor of 6.
>
>
>>When I've connected mine to my PC and recorded the readings over
>>extended periods of time the results have been in agreement with
>>the specifications.
>
>
> Of course - averaging kicks in. Duh...
No, I record each of the samples. The thousandth sample has no more
averaging than did the tenth. [BTW, this is not the case for
Magellan units which unfortunately do report internally averaged data.]
By having a large group of samples I can then see what the variation is
for 50% of the samples, 95% of the samples, 98% etc.
But the main thing that you've been claiming is that GPS can't be used
to measure fairly low velocities and that is simply not what I
observe every day when I go walking. The reading is very stable with
variations of only around +/- 0.1 mph when walking at a steady pace and
are consistent with my actual speed as determined by how long it takes
me to walk the 3.65 mile path. I also see that if I speed up a little
the GPS display goes up by a few tenths of a mph just as expected.
AFAICT, the same behavior occurs when using my GPS receiver on my
kayak deck where it gives me indications of my actual ground speed and
when I drift I get readings that are generally very consistent with the
expected tidal flow rates.
Sure I occasionally have seen glitches where the GPS displays an
incorrect value, probably due to multipath errors and switching of
which satellites are being used for the calculations. But such
glitches happen rarely, are short-lived, and are generally easy to
recognize and ignore.
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Date: 30 Sep 2004 13:39:07
From: Keenan Wellar
Subject: Re: Devices to Measure the Speed of Flowing Water?
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in article XY6dnTz5c7_aBcbcRVn-uA@comcast.com, Peter at prathman@comcast.net
wrote on 9/30/04 1:23 AM:
> Michael Daly wrote:
>> On 29--2004, Peter <prathman@comcast.net> wrote:
>>
>>
>>>> Leave your GPS sitting in one spot and watch the velocity change.
>>>
>>> It gets pretty boring watching the display that just says 0.0 knots
>>> for long periods of time with a few sporadic blips up to a few tenths
>>
>>
>> And I've seen mine wander around 3-7 kph for a while before settling down
>> to a smaller number lots of times. YMMV. Garmin 12XL.
>
> It would be nice to have some reasonable statistics to see how
> significant your "many" times are. When I've recorded data from
> my GPS receivers over thousands of samples such outliers occur
> only a few percent (and usually under 1%) of the time and are
> pretty obvious and easily discarded in practice.
> The existence of such occasional outliers is recognized in the
> accuracy specifications being given as holding for 95% or more
> of the samples.
>
> Another thing to note is that the 12XL is a pretty old design
> which was introduced in 1997 when expectations were that
> SA was going to be with us for the foreseeable future.
> As a result, I wouldn't be at all surprised if the firmware
> design wasn't quite as concerned with avoiding such small
> 'glitches' given that the effects of SA would frequently
> produce them anyway. But my experience with the Garmin 12
> is still that such outlier values are rather rare.
>
>>
>>
>>> Some, which is not surprising since the spec is for 95% of the readings,
>>> so once every 20 seconds or so one might expect a reading that's higher
>>> than the spec.
>>
>>
>> Not random, consistent. Again - YMMV.
>>
>> It's funny, ever since they turned off SA, so many people claim their
>> GPS readings are perfectly accurate. Turning off SA only increased the
>> accuracy by a factor of 6.
>>
>>
>>> When I've connected mine to my PC and recorded the readings over
>>> extended periods of time the results have been in agreement with
>>> the specifications.
>>
>>
>> Of course - averaging kicks in. Duh...
>
> No, I record each of the samples. The thousandth sample has no more
> averaging than did the tenth. [BTW, this is not the case for
> Magellan units which unfortunately do report internally averaged data.]
>
> By having a large group of samples I can then see what the variation is
> for 50% of the samples, 95% of the samples, 98% etc.
>
> But the main thing that you've been claiming is that GPS can't be used
> to measure fairly low velocities and that is simply not what I
> observe every day when I go walking. The reading is very stable with
> variations of only around +/- 0.1 mph when walking at a steady pace and
> are consistent with my actual speed as determined by how long it takes
> me to walk the 3.65 mile path. I also see that if I speed up a little
> the GPS display goes up by a few tenths of a mph just as expected.
> AFAICT, the same behavior occurs when using my GPS receiver on my
> kayak deck where it gives me indications of my actual ground speed and
> when I drift I get readings that are generally very consistent with the
> expected tidal flow rates.
>
> Sure I occasionally have seen glitches where the GPS displays an
> incorrect value, probably due to multipath errors and switching of
> which satellites are being used for the calculations. But such
> glitches happen rarely, are short-lived, and are generally easy to
> recognize and ignore.
I've found exactly the same. I'm in the process of moving so I can't tell
you which model I am using, it's packed away somewhere (I hope) but it's a
relatively new Garmin unit. I've experimented in similar fashion with
walking and paddling. If this penis-wagging contest is all about whether or
not you could use a GPS to measure the flow speed of a river, put me down
for "sure you could."
Will the resulting measurement stand up as undeniably precise when subjected
to to the most stringent scientific scrutiny? No. But that's not really the
question.
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Date: 28 Sep 2004 07:23:00
From: Peter
Subject: Re: Devices to Measure the Speed of Flowing Water?
|
Scott M. Knowles wrote:
> "W. Watson" <wolf_tracks@invalid.inv> wrote in message news:<82K4d.1491$zG1.928@newsread3.news.pas.earthlink.net>...
>
>>Is there a device or simple way to measure the speed of flowing water?
>
>
> Interesting discussion, but GPS, even precision GPS, won't work. The
> error in the GPS is far greater than the velocities you'll find. Most
> rivers flow between 1 and 6 feet per second, generally only exceeding
> during high flows, or near or through channel constrictions.
I take it you haven't used a GPS very much since the elimination of SA
four years ago. I use mine almost daily while walking and it shows my
usual 2.5 mph speed very well and correctly goes up to 3 or 3.5 if I
speed up a little. There is a noticeable time lag of a couple seconds
since it does a little averaging, but when moving steadily with
reasonable reception the displayed speed is accurate to about 0.1 - 0.2
mph. At the typical 3 - 4 mph speed of a river plus paddling speed
this gives your speed with only a small percentage error. I find it
most useful when seakayaking in areas with significant tides to be able
to check what my actual rate of progress is (or the tide speed if I drift).
BTW, GPS receivers do not depend on just positional changes to determine
velocities. They also measure the Doppler frequency shift of the
satellite signals.
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Date: 28 Sep 2004 10:48:42
From: Scott M. Knowles
Subject: Re: Devices to Measure the Speed of Flowing Water?
|
"Michael Daly" <michaelDaly@foo.bar > wrote:
> With SA it is 100m, 95% of the time. Without SA, it's 15m, 95% of the
> time. That means that 5% of the time, the error is larger.
Just a reminder, don't mistake resolution for accuracy. Just because
it's a number doesn't make it right, it has a probability-error band.
And it's still dependent upon the line you took for the measurement,
speed is just the value, velocity is a vectored speed. Interesting
potential application for GPS.
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Date: 28 Sep 2004 13:48:07
From: riverman
Subject: Re: Devices to Measure the Speed of Flowing Water?
|
"Scott M. Knowles" <scott@wsrphoto.com > wrote in message
news:a8d8f30.0409280403.52b7629d@posting.google.com...
> "W. Watson" <wolf_tracks@invalid.inv> wrote in message
> news:<82K4d.1491$zG1.928@newsread3.news.pas.earthlink.net>...
>> Is there a device or simple way to measure the speed of flowing water?
>
> Interesting discussion, but GPS, even precision GPS, won't work. The
> error in the GPS is far greater than the velocities you'll find. Most
> rivers flow between 1 and 6 feet per second, generally only exceeding
> during high flows, or near or through channel constrictions. If all
> you want it is the velocity in a river reach, you can use yourself
> (kayak) as floating debris, just time yourself without paddling
> through a reach, eg. 50-100 feet. But I haven't seen what you want to
> know.
Folks realize, of course, that mature sections of rivers worldwide flow on
average at about 4 mph? If they tend to flow over steeper terrain (hence,
faster current), they also tend to erode faster until the terrain flattens
out and they reach that magic number. If they flow over less steep terrain
(hence, slower current), they tend to deposit sediments until it gets
multiple shallower channels which, in turn, increase velocity until they
reach that magic number.
Near the headwaters, the flow might be faster than 4mph over short
stretches, but quickly gets to that when the flow volume increases and the
river starts downward-cutting. Near the mouth, the river has so much volume
that it flows quite fast for the gradient, and again it reaches that
velocity.
When I'm planning a trip on almost any floatable stretch, I bank on 4mph as
the 'resting flow rate'. This might not work for smaller sections, but for
almost any multiday trip, its quite an excellent constant.
--riverman
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Date: 28 Sep 2004 17:49:32
From: William R. Watt
Subject: Re: Devices to Measure the Speed of Flowing Water?
|
"riverman" (nospam@sorry.com) writes:
> When I'm planning a trip on almost any floatable stretch, I bank on 4mph as
> the 'resting flow rate'. This might not work for smaller sections, but for
> almost any multiday trip, its quite an excellent constant.
would not work on northern seasonal rivers such at the Yukon and Mackenzie.
--
--------------------
William R Watt National Capital FreeNet Ottawa's free community network
homepage: www.ncf.ca/~ag384/top.htm
warning: non-FreeNet email must have "notspam" in subject or it's returned
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Date: 29 Sep 2004 09:00:26
From: riverman
Subject: Re: Devices to Measure the Speed of Flowing Water?
|
"William R. Watt" <ag384@FreeNet.Carleton.CA > wrote in message
news:cjc87c$i8q$1@freenet9.carleton.ca...
>
> "riverman" (nospam@sorry.com) writes:
>
>> When I'm planning a trip on almost any floatable stretch, I bank on 4mph
>> as
>> the 'resting flow rate'. This might not work for smaller sections, but
>> for
>> almost any multiday trip, its quite an excellent constant.
>
> would not work on northern seasonal rivers such at the Yukon and
> Mackenzie.
Actually, it worked quite well on the Snake/Peel/Mackenzie the last time I
was up there. We put in on the headwaters of the Snake where the flow was
less than 1 mph, and took out on the main body of the Mackenzie where the
flow was likely close to 10kph. The overall length of our trip was about 300
miles, we spend 11 days and paddled about 6-8 hours a day (excluding
portages and lunch stops). That roughly corresponds to (300
miles/(7*11)hours)=3.9 mph. While we were floating, we definately spent much
more time on a brace than a stroke, so our average speed was a good
approximation of the average river velocity.
I use this 4mph estimate when planning longer trips. If I have, say 10 days
and want to paddle about 6 hours a day, I'll expect to cover (without
portages or lots of scouting) about 240 river miles. If there are lots of
little rapids, I lower my estimate to 3mph, and would expect to cover about
180 miles.
--riverman
(But I agree with your assessment that it is only a ballpark rate, and has
lots of variations)
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Date: 29 Sep 2004 13:07:48
From: William R. Watt
Subject: Re: Devices to Measure the Speed of Flowing Water?
|
"riverman" (nospam@sorry.com) writes:
> I use this 4mph estimate when planning longer trips. If I have, say 10 days
> and want to paddle about 6 hours a day, I'll expect to cover (without
> portages or lots of scouting) about 240 river miles. If there are lots of
> little rapids, I lower my estimate to 3mph, and would expect to cover about
> 180 miles.
I'm familiar with a 4 mph still water paddling speed, but isn't the
current usually added to that? For example, on a river such as the
Mississippi where the flow is a pretty consistent 4.5 mph the resulting
downstream speed is about 9 mph. The upstream paddling speed would be nil.
I suspect you are including more than river current and paddling speed into
your estimate.
--
--------------------
William R Watt National Capital FreeNet Ottawa's free community network
homepage: www.ncf.ca/~ag384/top.htm
warning: non-FreeNet email must have "notspam" in subject or it's returned
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Date: 29 Sep 2004 15:01:51
From: riverman
Subject: Re: Devices to Measure the Speed of Flowing Water?
|
"William R. Watt" <ag384@FreeNet.Carleton.CA > wrote in message
news:cjec34$7hr$1@freenet9.carleton.ca...
>
> "riverman" (nospam@sorry.com) writes:
>
>> I use this 4mph estimate when planning longer trips. If I have, say 10
>> days
>> and want to paddle about 6 hours a day, I'll expect to cover (without
>> portages or lots of scouting) about 240 river miles. If there are lots of
>> little rapids, I lower my estimate to 3mph, and would expect to cover
>> about
>> 180 miles.
>
> I'm familiar with a 4 mph still water paddling speed, but isn't the
> current usually added to that? For example, on a river such as the
> Mississippi where the flow is a pretty consistent 4.5 mph the resulting
> downstream speed is about 9 mph. The upstream paddling speed would be nil.
> I suspect you are including more than river current and paddling speed
> into
> your estimate.
Valid point, and I suspect that my rule of thumb probably takes into account
several errors cancelling themselves out.
For the Canadian rivers, I found that I spent a lot more time leaning on a
brace than paddling, and almost no time scouting, so my overall speed was
very close to the overall river velocity. However, for shorter 'lower-48'
trips, you're correct that you have to add paddling speed into the formula.
However, if you also add in the time spent on scouting, leg-stretching, etc,
it comes back to 4 mph again. The fact that this is close to average river
velocities is probably as much coincidence as it is from some 'rhythm of
nature'. The velocity that you <drift > in your boat is going to be less than
the average stream velocity, as the surface waters are slower, you tend to
snag eddys, etc. Paddling will increase that velocity beyond stream
velocity, but stops decreases it again.
How many times have you spent several days running a river, playing tag with
a recognizable log or peice of flotsam that just drifted along on its own
pace, until it got hung up on a rock or sweeper or something? I think this
observation is what got me thinking about this in the first place.
You know who might have some interesting input into this is someone
experienved with river S&R, or environmental hydrologist. If a dead body,
some pollutants or something is washed into the water, what is the average
rate that they plan on seeing it moving downstream?
--riverman
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Date: 28 Sep 2004 15:02:01
From: Michael Daly
Subject: Re: Devices to Measure the Speed of Flowing Water?
|
On 28--2004, "riverman" <nospam@sorry.com > wrote:
> Folks realize, of course, that mature sections of rivers worldwide flow on
> average at about 4 mph? [good explanation elided]
But if the mature river is in a rocky area, the average can be a lot less
and will not silt up quickly enough to change. The French River in Ontario
is in Laurentian Shield bedrock and is more like a lake in between the
whitewater sections. I've paddled lots of rivers that flow at somewhat
less than 4mph - so slow that GPS is definitely unreliable for speed
measures.
Mike
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Date: 28 Sep 2004 23:34:52
From: John R Weiss
Subject: Re: Devices to Measure the Speed of Flowing Water?
|
"Michael Daly" <michaelDaly@foo.bar > wrote...
>
> I've paddled lots of rivers that flow at somewhat
> less than 4mph - so slow that GPS is definitely unreliable for speed
> measures.
If it's that slow, its speed is probably irrelevant anyhow...
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Date: 29 Sep 2004 03:08:41
From: William R. Watt
Subject: Re: Devices to Measure the Speed of Flowing Water?
|
"John R Weiss" (jrweiss98155@.comNOSPAMcast.net) writes:
> "Michael Daly" <michaelDaly@foo.bar> wrote...
>>
>> I've paddled lots of rivers that flow at somewhat
>> less than 4mph - so slow that GPS is definitely unreliable for speed
>> measures.
>
> If it's that slow, its speed is probably irrelevant anyhow...
everthing is that slow when paddling. if you are paddling against a 4 mph
current you are not making much progress which would be one good reason to
want to measure the rate of flow.
--
--------------------
William R Watt National Capital FreeNet Ottawa's free community network
homepage: www.ncf.ca/~ag384/top.htm
warning: non-FreeNet email must have "notspam" in subject or it's returned
|
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Date: 29 Sep 2004 03:41:25
From: John R Weiss
Subject: Re: Devices to Measure the Speed of Flowing Water?
|
"William R. Watt" <ag384@FreeNet.Carleton.CA > wrote...
>
>>> I've paddled lots of rivers that flow at somewhat
>>> less than 4mph - so slow that GPS is definitely unreliable for speed
>>> measures.
>>
>> If it's that slow, its speed is probably irrelevant anyhow...
>
> everthing is that slow when paddling. if you are paddling against a 4 mph
> current you are not making much progress which would be one good reason to
> want to measure the rate of flow.
I get consistent velocity readouts on my GPS down to well under 1 knot. If it's
reading 0, it's likely moving at less than 1/4 knot.
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Date: 28 Sep 2004 16:46:28
From: riverman
Subject: Re: Devices to Measure the Speed of Flowing Water?
|
"Michael Daly" <michaelDaly@foo.bar > wrote in message
news:g4udnXWssNOt4cTcRVn-gQ@magma.ca...
>
> On 28--2004, "riverman" <nospam@sorry.com> wrote:
>
>> Folks realize, of course, that mature sections of rivers worldwide flow
>> on
>> average at about 4 mph? [good explanation elided]
>
> But if the mature river is in a rocky area, the average can be a lot less
> and will not silt up quickly enough to change. The French River in
> Ontario
> is in Laurentian Shield bedrock and is more like a lake in between the
> whitewater sections. I've paddled lots of rivers that flow at somewhat
> less than 4mph - so slow that GPS is definitely unreliable for speed
> measures.
>
> Mike
True, but technically speaking, a stretch of river that has intermittent
rapids and pool-like calm stretches is still relatively young, despite being
very old in actual years. You can even get a revitalized 'young' stretch
downstream of a chronologically older stretch, if uplift has happened in the
lower reaches of a watershed. ("Young" merely means that it is actively
downcutting.) Over time (a <long > time), the French River rapids will erode
down (even the metamorphics of the shield) and the calmer parts will gain
deposits, making it a mature river.
The 4mph estimate works best with rivers of a continuous gradient, or over
tremendously long stretches of river (like, in excess of half their total
length) to take into account the varying nature of different stretches.
There is a profile of a 'mature' river that has a characteristic
furved-wedge shape from source to mouth: exactly the same shape as a pile of
dust against a wall, or the edge of a sand dune: steep at the top, ramping
downward to a flat bottom. All along that shape, the velocity will be
approximately 4 mph.
In many cases, the 4mph is an interesting, but useless, factiod. But in
certain regions with all the rivers at the same maturity (like the Colorado
Plateau), you can use it quite dependably to estimate velocites on almost
any stretch of any river, as long as it is not over such a short stretch as
to change the characteristics of the river (such as just in Lava Falls; the
Colorado is essentially a flat, not whitewater, river).
--riverman
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Date: 29 Sep 2004 00:01:07
From: Blakely LaCroix
Subject: Riverman: One last trip.
|
Riverman:
Where are you these days? It was a busy summer, so I lost track. Last that I
recall, you had bailed out of the Congo and were in Wales going back to school.
It is always possible that I imagined that though. Hopefully you are still
out of harms way.
Facing the double nickels (55) next week. It is clear now that my life span
will not hold all of my dreams and goals. Pity that. So one must prioritize,
and that puts WorkerBee-ism pretty low on the list. Still, I show up every
day, but the motivation not to is much increased. Fact is we life way too
short a period of time.
So question for the group:
If you had one last trip what would it be? The reasons for last don't matter -
it could be anything from dying to being locked up in jail for violating the
Patriot Act, or selling ImClone stock.
Anarctica would be my choice, though not much paddling possible there.
The Nahanni or Yukon if I could convince my wife we wouldn't get eaten by
Bears.
Blakely
Blakely LaCroix
Minneapolis, Minnesota, USA.
RBP Clique member # 86.
The best adventure is yet to come.
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Date: 29 Sep 2004 08:07:57
From: Oci-One Kanubi
Subject: Re: Riverman: One last trip.
|
railtramp@aol.com (Blakely LaCroix) typed:
> [snip Myron stuff]
>
> So question for the group:
>
> If you had one last trip what would it be? The reasons for last don't
> matter - it could be anything from dying to being locked up in jail for
> violating the Patriot Act, or selling ImClone stock.
Well, first off, it couldn't possibly be for selling ImClone stock.
Nor for any other kind of market manipulation or tax evasion -- but
that's just my middle-class values talkin'.
OK, assuming good health and physical fitness, and no particular time
constraints, I'd go Washington to Washington; ocean to ocean.
I'd get a long, lightweight Bell or Winona canoe, a set of portage
wheels, and a folding bicycle, and rig a hitch to trail the wheeled
canoe behind the bike. I'd replace my two-man tent with a one-man
backpacker's tent, but also devise a stakeless lean-to system using
the boat and paddles (for awkward non-campsites). I'd replace my down
sleeping bags with a Hollofil bag. I've got a couple of big drybags
with packstraps and hipbelts, in which I'd pack my clothing and food,
and I'd buy at least two new Whisperlite stoves and at least two
backup Thermarests. I've got a ****load of polypro and down clothing,
and lotsa good summer wetware from that flyfishing-gear company, but
I'd probably want to start the trip with a brand new Goretex drysuit.
I'd leave Fletcher's Boat House on the tidal Potomac inside
Washington, DC city limits and paddle* up the Potomac to the North
Branch of the Potomac River, up the NB Potomac to the Savage River, up
the Savage and the Savage Reservoir to where there is a five- to
seven-mile portage (pulling the boat on the portage wheels along a
two-lane asphault road) across the Eastern Continental Divide to the
South Fork of the Casselman River.
I'd paddle* down the Casselman to the Youghiogheny, down the Yough to
the Monongahela, down the Monongahela to the Ohio, and down the Ohio
to the Mississippi.
I'd paddle* up the Mississippi to the Missouri, up the Missouri to the
Madison, and up the Madison to Hebgen Lake, where it is about a ten
mile portage (by road) across the Continental Divide to Henry's Lake.
(I'd expect to use the bicycle/wheeled-boat system to get around some
of the dams and/or dewatered stretches of the Missouri).
I'd paddle* down the Henry's Fork to the Snake River, Down the Snake
to the Columbia, and Down the Columbia to Astoria, OR on the Columbia
estuary, being sure to spend at least one night on the WA side in the
estuary.
Ideally I'd leave DC on January 1 of a mild winter and not be frozen
off the water before I hit the Mississippi in mid-spring. Getting up
the Mississippi at spring flood would be tough. Getting up the
Madison in late summer might be impossible. But I'd want to get
through Hell's Canyon and out of Idaho before the second Winter sets
in. A secondary goal would be to finish within one calendar year, but
if I had to weather over somewhere (er, ah... actually I'd let the
gear weather over while I flew to Tucson or San Diego!) I'd still call
it a success.
* and portage where necessary.
-Richard, His Kanubic Travesty
--
======================================================================
Richard Hopley Winston-Salem, NC, USA
rhopley[at]earthlink[dot]net
Nothing really matters except Boats, Sex, and Rock'n'Roll
rhopley[at]wfubmc[dot]edu
OK, OK; computer programming for scientific research also matters
======================================================================
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Date: 30 Sep 2004 07:15:19
From: Mike McCrea
Subject: Re: Riverman: One last trip.
|
rhopley@earthlink.net (Oci-One Kanubi) wrote
> OK, assuming good health and physical fitness, and no particular time
> constraints, I'd go Washington to Washington; ocean to ocean.
Richard, I hope to someday follow along vicariously as you undertake
that trip, maybe even accompany you for some small portion of the
upriver Potomac portion.
Yer not getting any younger you know...
I guess my last trip would be a reprise of my 1988-89 trip - take off
in my truck with my boat and gear and no firm plan, just following my
nose where whim and weather takes me for a year or two.
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Date: 29 Sep 2004 08:48:24
From: riverman
Subject: Re: Riverman: One last trip.
|
"Blakely LaCroix" <railtramp@aol.com > wrote in message
news:20040928200107.15036.00004137@mb-m02.aol.com...
> Riverman:
>
> Where are you these days? It was a busy summer, so I lost track. Last
> that I
> recall, you had bailed out of the Congo and were in Wales going back to
> school.
> It is always possible that I imagined that though. Hopefully you are
> still
> out of harms way.
>
> Facing the double nickels (55) next week. It is clear now that my life
> span
> will not hold all of my dreams and goals. Pity that. So one must
> prioritize,
> and that puts WorkerBee-ism pretty low on the list. Still, I show up
> every
> day, but the motivation not to is much increased. Fact is we life way too
> short a period of time.
>
> So question for the group:
>
> If you had one last trip what would it be? The reasons for last don't
> matter -
> it could be anything from dying to being locked up in jail for violating
> the
> Patriot Act, or selling ImClone stock.
>
> Anarctica would be my choice, though not much paddling possible there.
> The Nahanni or Yukon if I could convince my wife we wouldn't get eaten by
> Bears.
>
>
Hey rt:
No, you didn't imagine it. When the guns started going off in the spring, we
cancelled Final Exams and got the next plane out (disrupting my plans to go
to the interior for a week, including a 3-day canoe trip). I went to Wales,
met up with some Usenet friends and spent a week flyfishing, then a month in
Grad school in Cornwall. Then back to the US for a few weeks to tend to the
house, back to Sweden for a few weeks for some more wilderness exploring and
flyfishing, and now I'm back in Congo for one last year. Things here are
stable and quiet, but no one is fooled and the expectation is that if we get
out in the spring without any suprises, we'll be lucky.
Just passed the 46 milemarker myself, and the feeling that there's just too
many plans and too few days left is creeping up on me, too. Every ounce of
my being wanted to take a year off this year and get back into the old
lifestyle: buy a solid van and a new canoe, spend the daylight months in
Canada on the rivers, and then the winter months skiing and doing some
Mexican trips. But SWMBO was very adamant that if I left her in Congo (she
was not in a position to take a year off), she could not guarantee that we'd
still be together at the end of the year; so I got convinced to come back
for another year. It was *so* against all my old, reliable instincts, as I
feel like I just put another nail in the coffin and missed the last best
opportunity to get about 15 years younger and 20 pounds lighter... I also
wonder if life is going to be long enough for my own plans.
Last trip? Hmmm, I think about this one a lot. Having done so many through
the years, a big part of me feels like I don't need to add to any
credentials. Maybe a nice long float on the West Branch from Lobster Lake on
down to Ambejejus...just to smell the home waters again. But then, I read
stuff from folks like Dave Manby and realize that my own list of rivers is
pathetically tame and trivial, so maybe some new exploration like the Coruh,
Amazon or one of those unrun gems in Siberia.
I guess, most of all, I'm glad I don't have to choose 'one last river'. But
I suspect that when I <do > run my last river, I'll have no idea that it was
the one.
--riverman
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Date: 29 Sep 2004 11:18:43
From: Mike McCrea
Subject: Re: Riverman: One last trip.
|
"riverman" <nospam@sorry.com > wrote
> Maybe a nice long float on the West Branch from Lobster Lake on
> down to Ambejejus...
Riverman, isn't that what your will stipulates we do with your ashes?
Pour them loose into a scale model tripper and launch you onto the
West Branch from Lobster Trip on a crisp fall morning?
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Date: 30 Sep 2004 09:14:40
From: riverman
Subject: Re: Riverman: One last trip.
|
"Mike McCrea" <mccrea@umbi.umd.edu > wrote in message
news:b8fe2f84.0409291018.3be0d99@posting.google.com...
> "riverman" <nospam@sorry.com> wrote
>> Maybe a nice long float on the West Branch from Lobster Lake on
>> down to Ambejejus...
>
> Riverman, isn't that what your will stipulates we do with your ashes?
> Pour them loose into a scale model tripper and launch you onto the
> West Branch from Lobster Trip on a crisp fall morning?
I'm not sure if I should be asking my lawyer to investigate the leak or not,
but actually (all BS aside) that is almost <exactly > what my will
stipulates!! Half my ashes to be sent down the Grand Canyon and (illegally)
dumped in Marble Canyon, the other half sent down the Penobscot.
Specifically, I said off the bridge above Cribworks, but I think I'll modify
it and have myself sent down in a scale model tripper. I can spend some time
building the model myself...
--riverman
(spooky...)
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Date: 30 Sep 2004 08:16:07
From: Charles Pezeshki
Subject: Re: Riverman: One last trip.
|
in article 2s1tjnF1fvfmtU1@uni-berlin.de, riverman at nospam@sorry.com wrote
on 9/30/04 1:14 AM:
> Specifically, I said off the bridge above Cribworks, but I think I'll modify
> it and have myself sent down in a scale model tripper. I can spend some time
> building the model myself...
>
> --riverman
Hi Folks,
Well, now I know how I want to go--
I want my buddies to shove an empty pint of Old Crow down the bluejeans on
my carcass (they'll be expected to drink the WHOLE THING right before doing
so), wait for it to start raining and flooding, and throw my body into the
river next to the left bank of the New River outside Thurmond.
That way, I'm sure I'll snag up in a tree, just like the old hog I saw on my
first trip down the New at 6'.
Best,
Chuck
http://www.wildcountry.info
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Date: 30 Sep 2004 07:02:01
From: Mike McCrea
Subject: Re: Riverman: One last trip.
|
"riverman" <nospam@sorry.com > wrote
> I'm not sure if I should be asking my lawyer to investigate the leak or not,
> but actually (all BS aside) that is almost <exactly> what my will
> stipulates!! Half my ashes to be sent down the Grand Canyon and (illegally)
> dumped in Marble Canyon, the other half sent down the Penobscot.
> Specifically, I said off the bridge above Cribworks, but I think I'll modify
> it and have myself sent down in a scale model tripper. I can spend some time
> building the model myself...
>
> --riverman
> (spooky...)
What's really spooky is that I knew it would be a crisp fall day. I
really shouldn't have let that slip out. At least I didn't mention the
year ;-)
(Seriously, I think that would be a wonderfully fitting way to go,
ashes launched downstream in a scale model canoe, one last adventure
on the river. I'll have to amend my own will acordingly too)
|
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Date: 30 Sep 2004 15:13:48
From: riverman
Subject: Re: Riverman: One last trip.
|
"Mike McCrea" <mccrea@umbi.umd.edu > wrote in message >
> (Seriously, I think that would be a wonderfully fitting way to go,
> ashes launched downstream in a scale model canoe, one last adventure
> on the river. I'll have to amend my own will acordingly too)
Adventure is the right word. Think about how big a measly little 2' foot
wave looks in a 12" scale model canoe! And you wouldn't even have arms to do
a high brace!
--riverman
(Hell, for my luck, I'd dump on the eddy line....)
|
| | | | | | | | | | | |
Date: 30 Sep 2004 11:27:35
From: Mike McCrea
Subject: Re: Riverman: One last trip.
|
Riverman, the part of your will that I found most touching was this:
"I direct that Richard Hopley pay all of my funeral expenses, all
state and federal estate, inheritance and succession taxes,
administration costs and all of my debts subject to statute of
limitations as soon as practical after which I give, devise and
bequeath all of the rest, residue and remainder of my estate, of
whatever kind and character, and wherever located, to Mike McCrea"
Thanks bud.
|
| | | | | | | | | | | | |
Date: 04 Oct 2004 22:14:06
From: riverman
Subject: Re: Riverman: One last trip.
|
"Mike McCrea" <mccrea@umbi.umd.edu > wrote in message
news:b8fe2f84.0409301027.bb7a8c5@posting.google.com...
> Riverman, the part of your will that I found most touching was this:
>
> "I direct that Richard Hopley pay all of my funeral expenses, all
> state and federal estate, inheritance and succession taxes,
> administration costs and all of my debts subject to statute of
> limitations as soon as practical after which I give, devise and
> bequeath all of the rest, residue and remainder of my estate, of
> whatever kind and character, and wherever located, to Mike McCrea"
>
> Thanks bud.
No worries, but you got a bad suprise coming......
--riverman
(who says you can't take it with you...)
|
| | | | | | | | | | | | | |
Date: 05 Oct 2004 15:26:19
From: William R. Watt
Subject: Re: Riverman: One last trip.
|
"riverman" (nospam@sorry.com) writes:
> No worries, but you got a bad suprise coming......
how many cats can he carry in a kayak?
--
--------------------
William R Watt National Capital FreeNet Ottawa's free community network
homepage: www.ncf.ca/~ag384/top.htm
warning: non-FreeNet email must have "notspam" in subject or it's returned
|
| | | | | | | | | | | | | | |
Date: 06 Oct 2004 09:26:37
From: riverman
Subject: Re: Riverman: One last trip.
|
"William R. Watt" <ag384@FreeNet.Carleton.CA > wrote in message
news:cjueer$1sr$1@freenet9.carleton.ca...
>
> "riverman" (nospam@sorry.com) writes:
>
>> No worries, but you got a bad suprise coming......
>
> how many cats can he carry in a kayak?
>
Dunno, but I once carried 4 kayaks on a Cat(araft)
--riverman
|
| | | | | | |
Date: 29 Sep 2004 03:18:00
From: William R. Watt
Subject: Re: Riverman: One last trip.
|
Montreal to the mouth of the Columbia, a canoe trip and tribute to David
Thompson, mapmaker. It would cover just about every kind of water, and
the best of most kinds.
--
--------------------
William R Watt National Capital FreeNet Ottawa's free community network
homepage: www.ncf.ca/~ag384/top.htm
warning: non-FreeNet email must have "notspam" in subject or it's returned
|
| | | | | | | |
Date: 29 Sep 2004 09:14:07
From: riverman
Subject: Re: Riverman: One last trip.
|
"William R. Watt" <ag384@FreeNet.Carleton.CA > wrote in message
news:cjd9h8$me$1@freenet9.carleton.ca...
>
> Montreal to the mouth of the Columbia, a canoe trip and tribute to David
> Thompson, mapmaker. It would cover just about every kind of water, and
> the best of most kinds.
> --
>
After reading this, I want to change my 'last river'. I've always dreamed of
doing a trans-Canada....from Quebec to Alaska. Like the voyageurs, I could
see starting in Grand Portage to skip the St Lawrence and the Lakes, but
from GP to Alaska would be exquisite. Or the trip above...either one. Or
both.
--riverman
|
| | | | | | | | |
Date: 29 Sep 2004 19:15:19
From: Michael Daly
Subject: Re: Riverman: One last trip.
|
On 29--2004, "riverman" <nospam@sorry.com > wrote:
> Like the voyageurs, I could
> see starting in Grand Portage to skip the St Lawrence and the Lakes, but
> from GP to Alaska would be exquisite.
Start from Montreal and you'd skip the St. Laurence - the route was up the
Ottawa and then down the Mattawa to the French. From the French along the
North Shore of Georgian Bay is some of the best Great Lakes paddling there
is! Pukaskwa on Superior is one of the other great paddling destinations
in the Great Lakes. Don't short change yourself!
Mike
|
| | | | | | | |
Date: 28 Sep 2004 23:52:08
From: Keenan Wellar
Subject: Re: Riverman: One last trip.
|
in article cjd9h8$me$1@freenet9.carleton.ca, William R. Watt at
ag384@FreeNet.Carleton.CA wrote on 9/28/04 11:18 PM:
>
> Montreal to the mouth of the Columbia, a canoe trip and tribute to David
> Thompson, mapmaker. It would cover just about every kind of water, and
> the best of most kinds.
That sounds good.
I'll go for a circumnavigation of Newfoundland.
|
| |
Date: 27 Sep 2004 23:17:33
From: John R Weiss
Subject: Re: Devices to Measure the Speed of Flowing Water?
|
"W. Watson" <wolf_tracks@invalid.inv > wrote...
> Is there a device or simple way to measure the speed of flowing water?
If you're floating on it in your kayak, use a handheld GPS.
|
| |
Date: 27 Sep 2004 11:17:47
From: Scott M. Knowles
Subject: Re: Devices to Measure the Speed of Flowing Water?
|
"W. Watson" <wolf_tracks@invalid.inv > wrote in message news:<82K4d.1491$zG1.928@newsread3.news.pas.earthlink.net>...
> Is there a device or simple way to measure the speed of flowing water?
> --
What do you want to measure, speed or velocity, and from what, the
shore or your boat? There are a variety of current meters on the
market, from the standard Price AA and pgymy meters to ADCP's, with a
range of meters and electronic sensors, and the always timing
sticks/debris in the water (over a known distance). But as noted, the
velocity varys in the entire cross-section, which is why you take
numerous vertical and horizontal samples, usually averaged over a
period of time (30-60 seconds). A place to start is the USGS's
streamgaging manual at:
http://water.usgs.gov/pubs/wsp/wsp2175/
Other descriptions are at:
http://www.epa.gov/ORD/NRMRL/Pubs/600R01043/600R01043chap2.pdf (PDF)
http://www.fao.org/docrep/T0848E/t0848e-09.htm
http://gallatin.humboldt.edu/~brad/nws/lesson5.html - Excellent
description
Without more information of your needs, it's hard to say what will
work.
--Scott--
Scott M. Knowles "Opinions expressed are entirely my own."
scott@wsrphoto.com
Hydrologist, MS-Geography
"All things merge into one, and a river runs through it."
- Norman MacLean
|
| |
Date: 26 Sep 2004 16:34:39
From: Dave Manby
Subject: Re: Devices to Measure the Speed of Flowing Water?
|
Pitot tube will not measure the velocity (speed to you non scientists)
but will be a measure of the head
In message <24KdnaGKj-IbdsjcRVn-sg@magma.ca >, Michael Daly
<michaelDaly@foo.bar > writes
>On 25--2004, John-news-group <DO-NOT-USE-THIS-ADDRESS@123ZZE.CO.UK> wrote:
>
>> it's call a pedio tube.
>
>Pitot tube. Pronounced pee-toe.
>
>Mike
--
Dave Manby
Details of the Coruh river and my book "Many Rivers To Run" at
http://www.dmanby.demon.co.uk
|
| | |
Date: 21 Oct 2004 19:23:48
From: Jim Williams
Subject: Re: Devices to Measure the Speed of Flowing Water?
|
A simple way to measure velocity is to tie a cord to a twig and time the
payout.
"Dave Manby" <dave@dmanby.demon.co.uk > wrote in message
news:DUMA7TBPGuVBFw3T@dmanby.demon.co.uk...
> Pitot tube will not measure the velocity (speed to you non scientists)
> but will be a measure of the head
>
> In message <24KdnaGKj-IbdsjcRVn-sg@magma.ca>, Michael Daly
> <michaelDaly@foo.bar> writes
> >On 25--2004, John-news-group <DO-NOT-USE-THIS-ADDRESS@123ZZE.CO.UK>
wrote:
> >
> >> it's call a pedio tube.
> >
> >Pitot tube. Pronounced pee-toe.
> >
> >Mike
>
> --
> Dave Manby
> Details of the Coruh river and my book "Many Rivers To Run" at
> http://www.dmanby.demon.co.uk
>
|
| | | |
Date: 24 Oct 2004 16:01:44
From: Griffin
Subject: Re: Devices to Measure the Speed of Flowing Water?
|
Drop an orange in the main channel. Measure the time it takes to
float a known distance.
On Thu, 21 Oct 2004 19:23:48 GMT, "Jim Williams"
<james.h.williams1@att.net > wrote:
>A simple way to measure velocity is to tie a cord to a twig and time the
>payout.
>"Dave Manby" <dave@dmanby.demon.co.uk> wrote in message
>news:DUMA7TBPGuVBFw3T@dmanby.demon.co.uk...
>> Pitot tube will not measure the velocity (speed to you non scientists)
>> but will be a measure of the head
>>
>> In message <24KdnaGKj-IbdsjcRVn-sg@magma.ca>, Michael Daly
>> <michaelDaly@foo.bar> writes
>> >On 25--2004, John-news-group <DO-NOT-USE-THIS-ADDRESS@123ZZE.CO.UK>
>wrote:
>> >
>> >> it's call a pedio tube.
>> >
>> >Pitot tube. Pronounced pee-toe.
>> >
>> >Mike
>>
>> --
>> Dave Manby
>> Details of the Coruh river and my book "Many Rivers To Run" at
>> http://www.dmanby.demon.co.uk
>>
>
|
| |
Date: 24 Sep 2004 07:46:07
From: Randy Hodges
Subject: Re: Devices to Measure the Speed of Flowing Water?
|
"W. Watson" <wolf_tracks@invalid.inv >
> Is there a device or simple way to measure the speed of flowing water?
Wayne,
I worked with the Desert Reserch Institute on a flow study on the
Truckee river last year. We had a device (not likes simple or cheap)
that we could use to measure the velocity of the water at different
depths. I have seen the USGS people use a similar device when they
are calibrating the flow gauges.
You might give DRI a call.
Randy
|
| | |
Date: 29 Sep 2004 15:13:28
From: Bill Tuthill
Subject: Re: Devices to Measure the Speed of Flowing Water?
|
Randy Hodges <randallh@sonic.net > wrote:
>
> I worked with the Desert Reserch Institute on a flow study on the
> Truckee river last year. We had a device (not likes simple or cheap)
> that we could use to measure the velocity of the water at different
> depths. I have seen the USGS people use a similar device when they
> are calibrating the flow gauges. You might give DRI a call.
This thread has devolved into a guy-type discussion of GPS gadgetry
so I wanted to go back and ask about Randy's post.
Randy, must this device be used both in the center of the river
and on the sides?
Laminar flow theory says that water flows fastest in the center,
more slowly at the surface, much more slowly near the bottom,
and perhaps doesn't move at all near the banks.
I don't understand how any mathematical formula could expect to
accurately estimage CFS (or cumecs) from mere stage information,
especially at different flow levels. The riverbed could cause
laminar flows to vary unpredictably at high water.
|
| | |
Date: 24 Sep 2004 18:02:51
From: riverman
Subject: Re: Devices to Measure the Speed of Flowing Water?
|
"Randy Hodges" <randallh@sonic.net > wrote in message
news:3b41c027.0409240646.14c2eb28@posting.google.com...
> "W. Watson" <wolf_tracks@invalid.inv>
>> Is there a device or simple way to measure the speed of flowing water?
>
> Wayne,
>
> I worked with the Desert Reserch Institute on a flow study on the
> Truckee river last year. We had a device (not likes simple or cheap)
> that we could use to measure the velocity of the water at different
> depths. I have seen the USGS people use a similar device when they
> are calibrating the flow gauges.
>
> You might give DRI a call.
>
> Randy
You're talking about the little prop job? Not practical for boaters, I
think.
The way I use (other than just looking and guessing), is to toss something
like an orange overboard and have someone standing a known distance
downstream (50 meters, paced out.) Then time how long it takes to get there.
If its deep water and I'm drifting, I look for two landmarks on shore that I
can fairly well guestimate the distance between, and count how long it takes
to float between them. If I have a map (which is when I use this method the
most), I do it over a half-mile or so to get a good estimate. Gotta keep in
the center of the current during that time, but all the adjustments work out
to give a good estimate.
--riverman
|
| | | |
Date: 28 Sep 2004 09:46:58
From: Dave Manby
Subject: Re: Devices to Measure the Speed of Flowing Water?
|
The only times I have used a GPS and then only out of curiosity I have
definitely NOT been where the GPS has said that I am. I was definitely
not in the middle of Lake Van but on the shores of the lake. Lake Van is
Huge so it was not a matter of being out by a few metres.
Mind you Lake Van is in the Kurdish area of Turkey close to the Iraq
and Iran borders. The other time in Iran near the Iraq border it did not
work either!
OT Will You please tell your commander in chief to stop scrambling the
satellites or better still vote in a different one!
--
Dave Manby
Details of the Coruh river and my book "Many Rivers To Run" at
http://www.dmanby.demon.co.uk
|
| | | | |
Date: 30 Sep 2004 20:26:10
From: Don Freeman
Subject: Re: Devices to Measure the Speed of Flowing Water?
|
"Dave Manby" <dave@dmanby.demon.co.uk > wrote in message
news:O4cDwvACUSWBFwsC@dmanby.demon.co.uk...
> The only times I have used a GPS and then only out of curiosity I have
> definitely NOT been where the GPS has said that I am. I was definitely not
> in the middle of Lake Van but on the shores of the lake. Lake Van is Huge
> so it was not a matter of being out by a few metres.
>
Are you basing that on the Long/Lat displayed or from your position
graphically displayed on a mapping GPS device? If the latter it may be due
to your mapping software not being registered correctly. That's the case
with my Magellan Meridian, the MapSend Streets and Destinations software is
not exactly aligned and makes it appear that I am about 50 ft from where I
really am. This is only evident when I am zoomed it close enough to see the
offset.
|
| | | | | |
Date: 30 Sep 2004 22:07:33
From: John R Weiss
Subject: Re: GPS, velocity, and position errors [was: Devices to Measure the Speed of Flowing Water?]
|
> The only times I have used a GPS and then only out of curiosity I have
> definitely NOT been where the GPS has said that I am. I was definitely not in
> the middle of Lake Van but on the shores of the lake.
The base map on many GPS units is of pretty poor resolution. A lake shore may
be off by several hundred yards. Using the downloaded maps from a CD will
increase the resolution to a couple hundred feet or better.
|
| | | |
Date: 27 Sep 2004 23:04:30
From: Dave Manby
Subject: Re: Devices to Measure the Speed of Flowing Water?
|
>
>
>And why the heck does someone carry a GPS on a <river>? There can't be
>anything much simpler than finding where you are on a map if you already
>know you are on that little blue line. Even in the rain or at night, its
>just a matter of seeing what direction the water is flowing, and finding the
>corresponding bend on the map.
I got lost on a trip to Venezuela many years ago . We were paddling down
a tributary to get to the Orinoco. From there we would catch a boat to
get to the bottom of the rapids where there is a road around the rapids
(through Porto Ayachuco pardon the spelling) We then paddled the Maipure
and Apure rapids. This was back in 1977. Our petrol station map failed
to show that the tributary split and one branch joined the Orinoco BELOW
the port town where we were going to catch the boat upstream tot he road
head. Mind you a GPS would have been of no help - lack of satellites
then!
>
>
--
Dave Manby
Details of the Coruh river and my book "Many Rivers To Run" at
http://www.dmanby.demon.co.uk
|
| | | |
Date: 27 Sep 2004 10:54:53
From: Mtkkburk
Subject: Re: Devices to Measure the Speed of Flowing Water?
|
><wolf_tracks@invalid.inv>
>>> Is there a device or simple way to measure the speed of flowing water?
I didn't catch the beginning of the thread but did anyone mention a handheld
GPS? I have a simple, non-mapping Gecko 201 GPS. When I am interested in
seeing how fast the river is flowing I try to get the boat moving at the same
speed as flotsom on the surface of the water. When you page down through the
windows on the GPS you will find one with velocity in MPH or KPH. It is
interesting to see how your velocity changes as you move about the currents and
eddys on a river.
Now I realize that a canoe floating on the surface of a river doesn't always
move at the same rate as subsurface currents, but as a simple, rough measure it
is pretty quick and easy and can be done on the move at any time.
Mike
|
| | | | |
Date: 27 Sep 2004 15:54:15
From: Michael Daly
Subject: Re: Devices to Measure the Speed of Flowing Water?
|
On 27--2004, mtkkburk@aol.com (Mtkkburk) wrote:
> When you page down through the
> windows on the GPS you will find one with velocity in MPH or KPH. It is
> interesting to see how your velocity changes as you move about the currents and
> eddys on a river.
Unless the current is moving pretty quickly, the GPS speed changes
are likely errors in position reporting. It is only accurate to
15m, 95% of the time. You have to be moving fast enough for these
errors to be ignored.
Mike
|
| | | | | |
Date: 28 Sep 2004 00:29:25
From: William R. Watt
Subject: Re: Devices to Measure the Speed of Flowing Water?
|
on the subject of map reading, the topology looks a lot different from
water level than it does from the bird's eye view on the map. not the same
at all. all the indentations on the shoreline disappear into a single line
of trees. I can sometimes figure a river course ahead by studying the tops
of the trees. I really do need a compass to tell which way I'm headed so I
can find my position on the map. I've tried my own innate sense of
direction but when I thnk I'm paddling east the compass says I'm going
south.
on the subject of the maps themselves, for the local paddling I do I
photocopy topo maps at the public library, just the river course I'm
interested in, and avoid folding. A blue felt tipped pen does a good job
of highlighting the river course, and my own numbered and lettered circles
and arrows mark things like known obstructions and places where contour
lines cross the river. Right out of Bill Mason's books, except for the
photocopying part.
--
--------------------
William R Watt National Capital FreeNet Ottawa's free community network
homepage: www.ncf.ca/~ag384/top.htm
warning: non-FreeNet email must have "notspam" in subject or it's returned
|
| | | | | |
Date: 28 Sep 2004 00:19:58
From: Mtkkburk
Subject: Re: Devices to Measure the Speed of Flowing Water?
|
>Michael Daly wrote:
>Unless the current is moving pretty quickly, the GPS speed changes
>are likely errors in position reporting. It is only accurate to
>15m, 95% of the time. You have to be moving fast enough for these
>errors to be ignored.
>
>Mike
I don't know, you could be right. I know that it correlates pretty closely to
my cycle computer, but of course that is on a road at a slightly faster speed.
On the river, the speed variances make sense (in otherwords speed on the GPS is
greater when going through a section of the river where the current speeds up)
I have never done a calibration, but on the other hand I have never seen a
speed on the GPS that was obviously way off either.
Maybe someday I will try to check for accuracy by having a bicycle with a cycle
computer track me on one of our local rail trails that runs along the river.
Mike
|
| | | | | | |
Date: 28 Sep 2004 02:55:13
From: John R Weiss
Subject: Re: Devices to Measure the Speed of Flowing Water?
|
"Mtkkburk" <mtkkburk@aol.com > wrote...
>
>>Unless the current is moving pretty quickly, the GPS speed changes
>>are likely errors in position reporting. It is only accurate to
>>15m, 95% of the time. You have to be moving fast enough for these
>>errors to be ignored.
>
> I don't know, you could be right. I know that it correlates pretty closely to
> my cycle computer, but of course that is on a road at a slightly faster speed.
>
>
> On the river, the speed variances make sense (in otherwords speed on the GPS
> is
> greater when going through a section of the river where the current speeds up)
> I have never done a calibration, but on the other hand I have never seen a
> speed on the GPS that was obviously way off either.
If your GPS has a position error, it will likely be relatively constant over
small time/distance variations. That menas that even though it may not know
exactly where it is, it will not know where it is by about the same amount on
the next fix. Therefore, velocities will be reasonably accurate.
If your GPS shows a reasonably constant velocity over a straight track, you can
assume it will be a reasonably correct velocity.
One thing to watch out for at slow speeds is update rate. My Garmin GPS 3+ has
a "battery saver" feature that reduces the update rate from 5/second to
1/second. With the "battery saver" ON, velocities are NOT consistent when
moving slowly (e.g., in a kayak on a turning river). However, simply turning
the "battery saver" OFF smooths out the velocity readings and gives consistent
values.
|
| | | | | | | |
Date: 28 Sep 2004 05:04:11
From: Michael Daly
Subject: Re: Devices to Measure the Speed of Flowing Water?
|
On 27--2004, "John R Weiss" <jrweiss98155@.comNOSPAMcast.net > wrote:
> If your GPS has a position error, it will likely be relatively constant over
> small time/distance variations. That menas that even though it may not know
> exactly where it is, it will not know where it is by about the same amount on
> the next fix. Therefore, velocities will be reasonably accurate.
This is complete nonsense. The position errors are random and vary in direction
relative to the true position. If the errors were consistent, it would be easy
to eliminate them.
> velocities are NOT consistent when
> moving slowly (e.g., in a kayak on a turning river). However, simply turning
> the "battery saver" OFF smooths out the velocity readings and gives consistent
> values.
If the errors are there when in battery saver mode, they are there when not in
that mode. They don't go away, the rate of update just means the speed at
which they become important is lower. You are assuming that the speed of a
river will always be sufficient to ignore the errors. Bad assumption.
Mike
|
| | | | | | | | |
Date: 28 Sep 2004 22:49:13
From: John R Weiss
Subject: Re: Devices to Measure the Speed of Flowing Water?
|
"Michael Daly" <michaelDaly@foo.bar > wrote...
>
>> If your GPS has a position error, it will likely be relatively constant over
>> small time/distance variations. That menas that even though it may not know
>> exactly where it is, it will not know where it is by about the same amount on
>> the next fix. Therefore, velocities will be reasonably accurate.
>
> This is complete nonsense. The position errors are random and vary in
> direction
> relative to the true position. If the errors were consistent, it would be
> easy
> to eliminate them.
...and that is why many of the errors ARE eliminated! Almanac and Ephemeris
data transmitted with the GPS signal give the GPS receiver basic information
with which to make some of the corrections. Differential GPS, which is now
available on even cheap consumer-grade GPS receivers, corrects for most of the
remaining known error. A concise summary from
http://www.soe.ucsc.edu/~amin/research/thesis.pdf (page 60), which also
describes some of the common sources of error:
"most GPS errors vary slowly and are very strongly correlated within short
distances."
At http://www.edu-observatory.org/gps/gps_accuracy.html you will also find that
the significant sources of GPS error are predictable and correctable.
These are a very small sample of the info available on the web.
|
| | | | | | | | | |
Date: 29 Sep 2004 19:34:29
From: Michael Daly
Subject: Re: Devices to Measure the Speed of Flowing Water?
|
On 28--2004, "John R Weiss" <jrweiss98155@.comNOSPAMcast.net > wrote:
> ...and that is why many of the errors ARE eliminated!
And I'm referring to the errors that are still there _after_ these corrections
are applied.
> "most GPS errors vary slowly and are very strongly correlated within short
> distances."
A statement made without any reference to a source. How short is a short
distance?
> At http://www.edu-observatory.org/gps/gps_accuracy.html you will also find that
> the significant sources of GPS error are predictable and correctable.
I went to one of the links and the _measured_ error data was dated two days into
the future. This is reliable?
Mike
|
| | | | | |
Date: 27 Sep 2004 18:44:41
From: riverman
Subject: Re: Devices to Measure the Speed of Flowing Water?
|
"Michael Daly" <michaelDaly@foo.bar > wrote in message
news:27Kdnfg504ltq8XcRVn-pA@magma.ca...
> On 27--2004, mtkkburk@aol.com (Mtkkburk) wrote:
>
>> When you page down through the
>> windows on the GPS you will find one with velocity in MPH or KPH. It is
>> interesting to see how your velocity changes as you move about the
>> currents and
>> eddys on a river.
>
> Unless the current is moving pretty quickly, the GPS speed changes
> are likely errors in position reporting. It is only accurate to
> 15m, 95% of the time. You have to be moving fast enough for these
> errors to be ignored.
>
And why the heck does someone carry a GPS on a <river >? There can't be
anything much simpler than finding where you are on a map if you already
know you are on that little blue line. Even in the rain or at night, its
just a matter of seeing what direction the water is flowing, and finding the
corresponding bend on the map.
Now, for wandering in the woods where there are no landmarks, where you can
get all turned around, I can see the use of one. But I suspect that 99% of
GPS users on-river use it to find out where they are on the water, which
seems pretty lame to me.
Learn to use a compass! It doesn't require batteries, it works if it gets
wet, and it doesn't cost more than your life jacket!
--riverman
(And let the games begin....)
|
| | | | | | |
Date: 28 Sep 2004 16:22:04
From: Bill Tuthill
Subject: Re: Devices to Measure the Speed of Flowing Water?
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riverman <nospam@sorry.com > wrote:
>
> And why the heck does someone carry a GPS on a <river>? There can't be
> anything much simpler than finding where you are on a map if you already
> know you are on that little blue line. Even in the rain or at night, its
> just a matter of seeing what direction the water is flowing, and finding
> the corresponding bend on the map.
Ha ha ha! On the Escalante there are so many bends in a winding canyon
without visibility that it's impossible to tell where you are from a
topo map, unless you pay close attention at every bend.
> Now, for wandering in the woods where there are no landmarks, where you can
> get all turned around, I can see the use of one. But I suspect that 99% of
> GPS users on-river use it to find out where they are on the water, which
> seems pretty lame to me.
We did have a GPS, and used it, but it wasn't accurate enough to pinpoint
our location. We were either on one side of a horseshoe bend, or the other.
> Learn to use a compass! It doesn't require batteries, it works if it gets
> wet, and it doesn't cost more than your life jacket!
Good advice. If we had had a compass, we could have determined which side
of the bend we were on. Why do GPSes lack a compass? Seems odd to me.
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Date: 28 Sep 2004 12:48:44
From: Keenan Wellar
Subject: Re: Devices to Measure the Speed of Flowing Water?
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"Bill Tuthill" <can@spam.co > wrote in message
news:10lj3tc8a5u7kd6@corp.supernews.com...
> riverman <nospam@sorry.com> wrote:
>>
>> And why the heck does someone carry a GPS on a <river>? There can't be
>> anything much simpler than finding where you are on a map if you already
>> know you are on that little blue line. Even in the rain or at night, its
>> just a matter of seeing what direction the water is flowing, and finding
>> the corresponding bend on the map.
>
> Ha ha ha! On the Escalante there are so many bends in a winding canyon
> without visibility that it's impossible to tell where you are from a
> topo map, unless you pay close attention at every bend.
>
>> Now, for wandering in the woods where there are no landmarks, where you
>> can
>> get all turned around, I can see the use of one. But I suspect that 99%
>> of
>> GPS users on-river use it to find out where they are on the water, which
>> seems pretty lame to me.
>
> We did have a GPS, and used it, but it wasn't accurate enough to pinpoint
> our location. We were either on one side of a horseshoe bend, or the
> other.
>
>> Learn to use a compass! It doesn't require batteries, it works if it gets
>> wet, and it doesn't cost more than your life jacket!
>
> Good advice. If we had had a compass, we could have determined which side
> of the bend we were on. Why do GPSes lack a compass? Seems odd to me.
My GPS has a compass...I assumed most of them do?
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Date: 28 Sep 2004 00:25:35
From: Mtkkburk
Subject: Re: Devices to Measure the Speed of Flowing Water?
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>riverman wrote:
>And why the heck does someone carry a GPS on a <river>? There can't be
>anything much simpler than finding where you are on a map if you already
>know you are on that little blue line. Even in the rain or at night, its
>just a matter of seeing what direction the water is flowing, and finding the
>corresponding bend on the map.
>
>Now, for wandering in the woods where there are no landmarks, where you can
>get all turned around, I can see the use of one. But I suspect that 99% of
>GPS users on-river use it to find out where they are on the water, which
>seems pretty lame to me.
>
>Learn to use a compass! It doesn't require batteries, it works if it gets
>wet, and it doesn't cost more than your life jacket!
>
>--riverman
Wow, this is sad. No wonder nobody posts here anymore. Try to offer an answer
and you get dinged on your lifestyle!! Sheesh, sorry. |
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