GPS - Odometer vs Track Log ???

Author

Odometer vs Track Log ???

Mick

2007-08-21, 3:33 pm

Hi All,

Well I have finally plumped for an Off-Road GPS for my walks and last week
bought a Garmin Vista HCx and a copy of Memory-Map for the laptop. Anyway
I think the kit is great and at the weekend went for a short walk around
Chirk and Offas Dyke to test it all out before I go off to Scotland for a
week this coming weekend. Well now the reason for the post.....!!!

The Odometer reading for the walk I did is showing 5.02 miles but the
Track Log that was created is showing 6.47 miles..!! Now I know that
everything was reset before I started so why the difference?

Any feedback most appreciated. And if there is an obvious reason why then
I apologise in advance :)

--
Rgds, Mick.

R. Mark Clayton

2007-08-22, 7:33 am

Do you take big steps?

"Mick" <mick@127.0.0.1> wrote in message
news:memo.20070821185656.5616A@mick.zen.co.uk...
> Hi All,
>
> Well I have finally plumped for an Off-Road GPS for my walks and last week
> bought a Garmin Vista HCx and a copy of Memory-Map for the laptop. Anyway
> I think the kit is great and at the weekend went for a short walk around
> Chirk and Offas Dyke to test it all out before I go off to Scotland for a
> week this coming weekend. Well now the reason for the post.....!!!
>
> The Odometer reading for the walk I did is showing 5.02 miles but the
> Track Log that was created is showing 6.47 miles..!! Now I know that
> everything was reset before I started so why the difference?
>
> Any feedback most appreciated. And if there is an obvious reason why then
> I apologise in advance :)
>
> --
> Rgds, Mick.

CRet

2007-08-22, 7:33 am

Hi Mick,

Interresting is to compare lengths indicated by the two devises !

I alway take my eTrex Vista on when walking with friends and other members
of my local walk-club. We usely experiment a large dispersion of the length
indicated by the podometer(s) and in very rare occasion there is agreement
with the podometers and the GPS(s).

One more interresting fact is to compare values from the podometers, the GPS
and the length of walk computed from the map !

What we have to keep in mind that in all three cases, the lengths of the
walk are estimated (with different technology), but all are estimation
depending on how good are parameters et goodness of the mesurements.
- walk length from paper maps depend of scale, correct length mesurement,
precision and correct localisation of the way we have follow,
- topometer length greatly depend of calibration and heathness of the
walker which steps length may vary,
- GPS track log or odometry computer depend of sample rate and position
accuracy.

All these factors, accuracy of mesuremnt, correct parametrs, length of the
walk, diffculties, weather, good joke, landscape, etc are all subject to the
long discussions and debate we have during hours after each walking day at
the arrival café !

Having 1.45 miles off is, from my opinion, quite a large error, depending of
the overall length of the walk.
Most of the time, we observe variations of about 2-3 km (1.25 - 1.86 mi) for
a about 20-25 km (12.4-15.5 mi) long walk between GPS and good podometers
(on easy terrain with good calibrated podometer).

On easy walk (flat terrain), GPS over estimate length compare to topometer
since walker tendency is to increase steps length.
On difficult terrain (going up and down), generally topometers over estimate
length du to shorter stelp leng of walker tired or in difficulties.
On high mountain walk or trecking, podometers are generaly out due to
unregular walk on high mountain pathway.

On open field, GPS odometry is good since reception is OK. In forest or town
, by poor satellite reception, accuracy drop down, but the tendancy of the
GPS is to over-estimate the length by introducing erronous point in the
track. At low sample rate, GPS underestimate length due to lack of acquired
points. At high sampling rate, more noise is introduced in the computation,
which lead to over-estimated the length of the walk.

Best accuracy of the length from the Track Log is obtain by removing extra
and erronous (outlier) points by drawing the track back on the map. We
generaly observe less than 1 km off from filtered Track Log compare from
length measered on electronic topo maps (1/25000) for a 20/25 km long trip.
Error in measuring length on paper map is mainly due to lack of precision
and mecanic sliding ball of the measuring roller in the curvimeter.

Hope this feedback may help concidering walk length measurements !

C.Ret

Reference : "Mick" <mick@127.0.0.1> in
news:memo.20070821185656.5616A@mick.zen.co.uk...

Marcus Fox

2007-08-22, 7:33 am

"Mick" <mick@127.0.0.1> wrote in message
news:memo.20070821185656.5616A@mick.zen.co.uk...
> Hi All,
>
> Well I have finally plumped for an Off-Road GPS for my walks and last week
> bought a Garmin Vista HCx and a copy of Memory-Map for the laptop. Anyway
> I think the kit is great and at the weekend went for a short walk around
> Chirk and Offas Dyke to test it all out before I go off to Scotland for a
> week this coming weekend. Well now the reason for the post.....!!!
>
> The Odometer reading for the walk I did is showing 5.02 miles but the
> Track Log that was created is showing 6.47 miles..!! Now I know that
> everything was reset before I started so why the difference?
>
> Any feedback most appreciated. And if there is an obvious reason why then
> I apologise in advance :)
>
> --
> Rgds, Mick.

Did you walk in a straight line? Perhaps you did walk 6.47 miles, but ended
up 5.02 miles from where you started off.

Marcus

Pete Rissler

2007-08-22, 10:33 am

"Mick" <mick@127.0.0.1> wrote in message
news:memo.20070821185656.5616A@mick.zen.co.uk...
> Hi All,
>
> Well I have finally plumped for an Off-Road GPS for my walks and last week
> bought a Garmin Vista HCx and a copy of Memory-Map for the laptop. Anyway
> I think the kit is great and at the weekend went for a short walk around
> Chirk and Offas Dyke to test it all out before I go off to Scotland for a
> week this coming weekend. Well now the reason for the post.....!!!
>
> The Odometer reading for the walk I did is showing 5.02 miles but the
> Track Log that was created is showing 6.47 miles..!! Now I know that
> everything was reset before I started so why the difference?
>
> Any feedback most appreciated. And if there is an obvious reason why then
> I apologise in advance :)
>
> --
> Rgds, Mick.

It's a bug in the Vista HCx, if you walk below a certain speed it will not
record your distance. Search the Groundspeak forum for more info.

http://forums.groundspeak.com/GC/in...f4&showforum=11

hermans

2007-08-22, 10:33 am

Mick's observation is correct. It's not only a problem for the Vista HCx
but also for the 60CSx. Take a look at the time recording for the track:
time stopped and time moved. But normally in this case I observe that
the track length is less than the trip length. Perhaps you can put your
track onto a map and look if there are no anomalies in the registration
(track point a distance away of the path you walked).
A comparison to podometers isn't very helpful because podometers work
with the number of steps you have taken and a mean value of the step
length. If you walk on difficult ground and your step length varies
much, the result isn't very accurate.
Pete Rissler schreef:
> "Mick" <mick@127.0.0.1> wrote in message
> news:memo.20070821185656.5616A@mick.zen.co.uk...
>
> It's a bug in the Vista HCx, if you walk below a certain speed it will not
> record your distance. Search the Groundspeak forum for more info.
>
> http://forums.groundspeak.com/GC/in...f4&showforum=11
>
>

Jack Erbes

2007-08-22, 10:33 pm

Mick wrote:
> Hi All,
>
> Well I have finally plumped for an Off-Road GPS for my walks and last week
> bought a Garmin Vista HCx and a copy of Memory-Map for the laptop. Anyway
> I think the kit is great and at the weekend went for a short walk around
> Chirk and Offas Dyke to test it all out before I go off to Scotland for a
> week this coming weekend. Well now the reason for the post.....!!!
>
> The Odometer reading for the walk I did is showing 5.02 miles but the
> Track Log that was created is showing 6.47 miles..!! Now I know that
> everything was reset before I started so why the difference?
>
> Any feedback most appreciated. And if there is an obvious reason why then
> I apologise in advance :)

Did you clear the track and also immediately reset the odometer? And
did you save the track at the same moment (within a few seconds or so)
of the time you saw the 5.02 reading?

Try it again clearing the track and zeroing the odometer just as you
start. When you get the ending place, note the distance on the odometer
and then turn the GPS off and back on. The off/on cycle will start a
new track segment on the *.gpx file track log. So when you look at the
*.gpx file that segment should show the same distance you saw on the
odometer.

Whenever the GPS is on it is calculating fixes, like about one per
second or so. Each fix is in a different place, even when the GPS has
not moved physically. The distance from one fix point to another is
steadily accumulated by the odometer and if that goes on long enough it
skews the numbers.

Clear you odometer and leave it laying somewhere for a while, you'll be
surprised how much distance can be accumulated.

When I want accurate starting and ending times and distances, I look at
the *.gpx files on the memory card. Those will not accumulate all the
track points when you are stationary, it uses a speed threshold or
something to stop and start on saving track points. Looking at that I
can see when movement starts and stops and I can also get the distance,
speed, and average speed info from it by looking at the track properties
in MapSource or GPS Utility.

By copying and pasting portions of the track data into a second
MapSource window, I can isolate parts of a track to analyze portions of
a track or to break one long track into several shorter tracks. And I
can edit out track points, join tracks, and do similar things.

Turn the Log Track to Data Card thing on if it is not on already. The
saved tracks are useless for post travel analysis because then do not
contain the time data. And they are limited to 400 track points
(selected by the software) regardless of the length of the track or the
number of points collected.

Jack

A. N. Other

2007-08-23, 7:33 am

From my experiments there is a problem with the odometer in the Vista HCx.

When deliberately walking very slow, below 3kmh, and going on a defined
track the odometer displayed .4Km. On returning over the same track, walking
fast, the distance indicated was 1.2 Km. The tracks recorded showed the
approximately same distance in both cases, 1.2Km.

"Mick" <mick@127.0.0.1> wrote in message
news:memo.20070821185656.5616A@mick.zen.co.uk...
> Hi All,
>
> Well I have finally plumped for an Off-Road GPS for my walks and last week
> bought a Garmin Vista HCx and a copy of Memory-Map for the laptop. Anyway
> I think the kit is great and at the weekend went for a short walk around
> Chirk and Offas Dyke to test it all out before I go off to Scotland for a
> week this coming weekend. Well now the reason for the post.....!!!
>
> The Odometer reading for the walk I did is showing 5.02 miles but the
> Track Log that was created is showing 6.47 miles..!! Now I know that
> everything was reset before I started so why the difference?
>
> Any feedback most appreciated. And if there is an obvious reason why then
> I apologise in advance :)
>
> --
> Rgds, Mick.
>

Ian Rawlings

2007-08-23, 7:33 am

On 2007-08-23, A. N. Other <a@privacy.net> wrote:

> When deliberately walking very slow, below 3kmh, and going on a
> defined track the odometer displayed .4Km. On returning over the
> same track, walking fast, the distance indicated was 1.2 Km. The
> tracks recorded showed the approximately same distance in both
> cases, 1.2Km.

I know that on mine, when it thinks I'm stationery it tells me so on
the screen (time spent travelling and time spent stationery) and stops
adding to the distance, normally I'm on my bike though so not sure if
it kicks in when walking.

Also the track log granularity can change depending on settings, so
perhaps it's measuring straight-line distances between points that are
missing out a few of the small turns and twists. That would make it
read less though, but could be another source of difference between
the two.

--
Blast off and strike the evil Bydo empire!

Mark Olson

2007-08-23, 10:33 am

Ian Rawlings wrote:
> On 2007-08-23, A. N. Other <a@privacy.net> wrote:
>
>
>
>
> I know that on mine, when it thinks I'm stationery it tells me so on

.... a little piece of note paper?

Ian Rawlings

2007-08-23, 10:33 am

On 2007-08-23, Mark Olson <olsonm@tiny.invalid> wrote:

>
> ... a little piece of note paper?

Ha ha, I thought about that for a while to make sure I didn't get the
wrong one, but didn't bother to check the dictionary inches from my
hand..

I'll make a note on some stationary.

--
Blast off and strike the evil Bydo empire!

Mick

2007-08-23, 12:33 pm

"Mick" <mick@127.0.0.1> wrote:

> Any feedback most appreciated. And if there is an obvious reason why
> then I apologise in advance :)

Thanks for all the answers it made interesting reading and gave me some
food for thought. I didn't get chance to play last night due to work
commitments (why does work get in the way of my hobbies??) but have just
managed to have a detailed look at the track. I think that most of the
error is at the points where we stopped for a food break etc because there
are loads of spikes (is this the spider web problem?) around those points
which obviously all add to the distance.

I will do a lot more testing next week whilst in Scotland.

Just one thing though; what do people have the track log recording method
set to? Mine was set to auto but was thinking that if I set it to distance
then at the points where we stop then it should (I think???) not record
these spikes!! or am I missing something??

--
Rgds, Mick.

Paul Saunders

2007-08-23, 10:33 pm

Mick wrote:

> have just managed to have a detailed look at the track. I think that
> most of the error is at the points where we stopped for a food break
> etc because there are loads of spikes (is this the spider web
> problem?) around those points which obviously all add to the distance.

Where did you put the GPS when you stopped? Spikes can easily happen when
you stop if you place the GPS in a position where reception is poor. For
example, mine is attached to my rucksack strap, so when I stop and take my
rucksack off, if I'm not careful the GPS can end up mostly covered by the
rucksack.

> Just one thing though; what do people have the track log recording
> method set to?

I usually set mine to Auto - most detail. For longer trips I'd reduce the
detail, but 10,000 points is more than enough for short trips.

> Mine was set to auto but was thinking that if I set it
> to distance then at the points where we stop then it should (I
> think???) not record these spikes!! or am I missing something??

Yep, you're missing something, the reception problem mentioned above. If you
make sure the GPS is getting good reception when you stop, it shouldn't add
any points. It doesn't with mine.

On the other hand, if you set it to distance it would miss something, all
the little twists and turns below the distance threshold.

Setting it to time also misses the twists and turns, and accumulates lots of
points whenever you stop, so that's even worse.

Auto is best because it places points whenever it detects changes in
direction, so it records all the little twists and turns (more if you set
the detail to most), but if you walk in a straight line the points are
spaced much further apart, so you get the best compromise between detail and
efficiency (not using more points than are necessary).

If you want to test how much detail is recorded in twists and turns, try
recording a track whilst walking in a circle (I've done this walking around
a small hill fort to record the shape). Try it on different detail settings
to see the difference.

And don't forget, when you stop, make sure it's getting a good signal, and
if not, just turn it off for a while.

Paul
--
http://www.wilderness-wales.co.uk/
http://www.wilderness-wales.co.uk/weblog/

Mick

2007-08-23, 10:33 pm

"Paul Saunders" <pvs1@wildwales.fsnet.co.uk> wrote:

> Where did you put the GPS when you stopped? Spikes can easily happen
> when you stop if you place the GPS in a position where reception is
> poor. For example, mine is attached to my rucksack strap,

Yes I had attached mine to the strap also so I guess that it didn't have
much of a signal at that point.

> Auto is best because it places points whenever it detects changes in
> direction, so it records all the little twists and turns (more if you
> set the detail to most), but if you walk in a straight line the points
> are spaced much further apart, so you get the best compromise between
> detail and efficiency (not using more points than are necessary).

> And don't forget, when you stop, make sure it's getting a good signal,
> and if not, just turn it off for a while.

Thanks points noted. Like I said I am new to this GPS walking tool :)

--
Rgds, Mick.

Mick

2007-08-23, 10:33 pm

"Mick" <mick@127.0.0.1> wrote:

> Any feedback most appreciated. And if there is an obvious reason why
> then I apologise in advance :)

Well I have just had another play. The total point-to-point distance of
the route in Memory Map is 5.8 miles and now that I have cleaned up the
track log by removing the strange points the distance is now 6.2 miles
which I think is about right looking at the route actually taken.

So in conclusion I guess the odometer (which read 5.02 miles) is
rubbish!!!

--
Rgds, Mick.

Bill Grey

2007-08-23, 10:33 pm

In message < uvGdnWSR9vKzbVDbnZ2d
nUVZ8tChnZ2d@pipex.net>, Paul Saunders
<pvs1@wildwales.fsnet.co.uk> writes
>
>Where did you put the GPS when you stopped? Spikes can easily happen when
>you stop if you place the GPS in a position where reception is poor. For
>example, mine is attached to my rucksack strap, so when I stop and take my
>rucksack off, if I'm not careful the GPS can end up mostly covered by the
>rucksack.

Interestingly, I had the opportunity to have a lift in Sea King
recently and was using my Holux Bluetooth GPS in conjunction with my PDA
with MM. To safeguard the equipment I put both into my riucksack as
getting into the Sea King is an ordeal for me :-)

The GPS recorded the flight back to our car park, and after I placed the
rucksack in the boot of my car, it also recorded the track back to
Brecon from Torpantau.

It was in contradiction of all the " good view of the sky" advice we
get, I could hardly believe it.
--
Bill Grey

Jack Erbes

2007-08-23, 10:33 pm

Mick wrote:
<snip>
> managed to have a detailed look at the track. I think that most of the
> error is at the points where we stopped for a food break etc because there
> are loads of spikes (is this the spider web problem?) around those points
> which obviously all add to the distance.

Are you looking at the track downloaded from track memory or at a *.gpx
file from the microSD card. You might find it interesting to compare
those two.

I didn't mention it before, it had slipped my mind, but the behavior
will change quite a bit depending on your choice of time or distance for
the Record Method. I generally use Distance and that will avoid those
spider webs from occurring. And that is also what accounts for the
behavior I mentioned where points stop being added to the *.gpx files
when I stop moving.

When I set the Record Method to time I see those spider webs when I zoom
in on the display when my receiver (GPSmap 76Cx) is on and has been
setting. And the same spider web will also, of course, be in track
memory and in the *.gpx file on the microSD card too.

> Just one thing though; what do people have the track log recording method
> set to? Mine was set to auto but was thinking that if I set it to distance
> then at the points where we stop then it should (I think???) not record
> these spikes!! or am I missing something??

It will stop the collection. At least unless two of the track points
are far enough to meet or exceed the distance setting. That should help
resolve some of the issues for you. I'm not sure that it is the same
for all models and I certainly don't feel that I've figured it all out.
So the results of your tests will be interesting.

On the distance setting, I set it to auto for most purposes. If I want
more points I usually use .01 or .02 miles. Those give me 100 or 50
points per mile respectively and that works fine for collecting tracks
for power boats, motorcycles, cars, and the like. If I were moving more
slowly, like on foot, and wanted more points, I might use the time method.

But whenever you use the time method the spider webs will occur when you
are not moving.

Jack

Mike Coon

2007-08-23, 10:33 pm

Ian Rawlings wrote:
> On 2007-08-23, Mark Olson <olsonm@tiny.invalid> wrote:
>
>
> Ha ha, I thought about that for a while to make sure I didn't get the
> wrong one, but didn't bother to check the dictionary inches from my
> hand..
>
> I'll make a note on some stationary.

It's easy if you remember "stationer"...

HTH, Mike.
--
If reply address = connectfee, add an r because it is free not fee.

Dan Anderson

2007-08-24, 4:33 am

Mick wrote:
> Well I have just had another play. The total point-to-point distance of
> the route in Memory Map is 5.8 miles and now that I have cleaned up the
> track log by removing the strange points the distance is now 6.2 miles
> which I think is about right looking at the route actually taken.
>
> So in conclusion I guess the odometer (which read 5.02 miles) is
> rubbish!!!

The HCx models have a current bug in that they don't accumulate
distance in the odometer if you walk to slow. The track log
distance should be fine if any "noise" is removed.

--
Dan
(email change 2001 to 2004)
(www.gpsmap.net)

Paul Saunders

2007-08-24, 4:33 am

Jack Erbes wrote:

> On the distance setting, I set it to auto for most purposes. If I
> want more points I usually use .01 or .02 miles. Those give me 100
> or 50 points per mile respectively and that works fine for collecting
> tracks for power boats, motorcycles, cars, and the like. If I were
> moving more slowly, like on foot, and wanted more points, I might use
> the time method.

I'd recommend plain auto for walking. You'll miss a lot of small twists and
turns with the time and distance methods, it's surprising how many there can
be. You'll end up with a shorter distance than you actually walked, unless
of course there aren't many twists and turns in your walks (there usually
are with mine).

> But whenever you use the time method the spider webs will occur when
> you are not moving.

Not if you make sure you have good reception when you stop. I just checked
my last track where I left my GPS on top of a trig point for 5 minutes with
a clear view of the sky, and the track only recorded 2 points there, one
when I arrived and one when I left. On an earlier walk I stopped for 15
minutes in the shelter on top of Fan Brycheiniog and it recorded 12 points,
but the reception obviously wasn't so good there.

If webs are that much of a problem for you, just switch it off when you
stop. Unless the spikes cover large distances they won't add much to the
total distance anyway. IMO you'll lose a lot more distance from distance
recording than you'll gain from auto recording, unless the spikes are really
bad, in which case you can just edit them out later. If I know I was
stationary from point 356 to point 372, it's a simple matter to delete the
points in between. But you can't add all the little twists and turns that
weren't recorded.

Paul
--
http://www.wilderness-wales.co.uk/
http://www.wilderness-wales.co.uk/weblog/

Paul Saunders

2007-08-24, 4:33 am

Mick wrote:

> Well I have just had another play. The total point-to-point distance
> of the route in Memory Map is 5.8 miles and now that I have cleaned
> up the track log by removing the strange points the distance is now
> 6.2 miles which I think is about right looking at the route actually
> taken.
>
> So in conclusion I guess the odometer (which read 5.02 miles) is
> rubbish!!!

No, it's just that when you lose reception, or if you're walking
particularly slowly, the odometer stops recording. On most of my walks the
odometer and track distances are pretty similar, the difference is not
enough to bother me. A big difference is usually down to bad reception, in
which case I usually trust the track distance rather than the odometer, but
it's important to check the track and delete the inevitable spurious points
if that's the case. If a track is really messed up, it may be simpler to
draw a new track over the top to find out the distance.

Messed up tracks are in the minority though, in my experience. I usually get
them in forested valleys, but most of my walks are in quite open ground so
it's rarely a problem.

As for the odometer speed threshold, below which it stops recording
distance, it's 1.6kph (1mph) on both of the models I've owned. It may be
different on other models, but I'd guess that all Garmins are set to that.
It's easy to check, just walk slower and slower and watch the speed readout.
As you drop below 1.6kph it suddenly reads 0kph, even though you're still
moving. This is a clear indication that the odometer has stopped recording.
I've often seen this when climbing particularly steep slopes or crossing
extremely rough ground (not that it's a good idea to stare at your GPS in
the latter case!)

As a side note, this speed threshold is also what stops the compass display
working correctly (in most GPS models that don't have a built in electronic
compass). You have to be moving at least 1.6kph for the GPS to detect which
direction it's moving in, and hence for the compass display to work and the
GOTO arrow to point in the right direction.

Paul
--
http://www.wilderness-wales.co.uk/
http://www.wilderness-wales.co.uk/weblog/

Chris Game

2007-08-24, 7:33 am

On Thu, 23 Aug 2007 22:55:15 +0100, Bill Grey wrote:

> The GPS recorded the flight back to our car park, and after I
> placed the rucksack in the boot of my car, it also recorded the
> track back to Brecon from Torpantau.

How did it see through the boot lid?

--
Chris Game

To iterate is human; to recurse, divine.

willshak

2007-08-24, 7:33 am

on 8/23/2007 3:37 PM Mike Coon said the following:
> Ian Rawlings wrote:
>
>
> It's easy if you remember "stationer"...
>
> HTH, Mike.
>

A 'stationer' (with an E) is one that supplies book materials and
writing materials, such as stationary (with an A).

--

Bill
In Hamptonburgh, NY
To email, remove the double zeroes after @

Alan White

2007-08-24, 10:33 am

On Thu, 23 Aug 2007 22:55:15 +0100, Bill Grey
<wdg@graigroad.demon.co.uk> wrote:

>It was in contradiction of all the " good view of the sky" advice we
>get, I could hardly believe it.

We experienced this on Wednesday after I forgot to switch off my GPSmap
60c. It was a bit irritating because the track log was quite important.

The signal probably entered the car through the windows and went through
the rear seat back into the boot.

--
Alan White
Mozilla Firefox and Forte Agent.
Twenty-eight miles NW of Glasgow, overlooking Lochs Long and Goil in Argyll, Scotland.
Webcam and weather:- http://windycroft.gt-britain.co.uk/weather

Ian Rawlings

2007-08-24, 10:33 am

On 2007-08-24, willshak <willshak@00hvc.rr.com> wrote:

> A 'stationer' (with an E) is one that supplies book materials and
> writing materials, such as stationary (with an A).

Stationery is pens 'n' paper, Stationary is "not moving", according to
the OED which I should have checked as soon as I knew I was getting
confused..

--
Blast off and strike the evil Bydo empire!

Jack Erbes

2007-08-24, 10:33 am

Paul Saunders wrote:
> Jack Erbes wrote:
>
>
> I'd recommend plain auto for walking. You'll miss a lot of small twists and
> turns with the time and distance methods, it's surprising how many there can
> be. You'll end up with a shorter distance than you actually walked, unless
> of course there aren't many twists and turns in your walks (there usually
> are with mine).

If you set it for time and one or two seconds, you'll not miss much if
anything. You'll use up the track memory pretty quickly (2.78 hours?)
but if you're also logging the track to the memory card you'll not lose
any data on trips that take more time than that.

>
> Not if you make sure you have good reception when you stop. I just checked
> my last track where I left my GPS on top of a trig point for 5 minutes with
> a clear view of the sky, and the track only recorded 2 points there, one
> when I arrived and one when I left. On an earlier walk I stopped for 15
> minutes in the shelter on top of Fan Brycheiniog and it recorded 12 points,
> but the reception obviously wasn't so good there.

And was that with the Record Method set to time or distance? When I
have it set to time, I get a spider web. With it set to distance, I do
not.

> If webs are that much of a problem for you, just switch it off when you
> stop. Unless the spikes cover large distances they won't add much to the
> total distance anyway. IMO you'll lose a lot more distance from distance
> recording than you'll gain from auto recording, unless the spikes are really
> bad, in which case you can just edit them out later. If I know I was
> stationary from point 356 to point 372, it's a simple matter to delete the
> points in between. But you can't add all the little twists and turns that
> weren't recorded.

To see tracks that are accurate as far as time, distance, and path
actually traveled, that is where I wind up in MapSource and editing the
*.gpx files to remove superfluous track points, join track segments, and
the like. Then when I look at the track properties I see time and
distance values that are accurate.

To see and get the statistics for portions of a longer track, I copy the
track points and paste them into a new MapSource window.

Jack

dino

2007-08-24, 10:33 am

Bill Grey wrote:
> In message < uvGdnWSR9vKzbVDbnZ2d
nUVZ8tChnZ2d@pipex.net>, Paul Saunders
> <pvs1@wildwales.fsnet.co.uk> writes
>
> Interestingly, I had the opportunity to have a lift in Sea King
> recently and was using my Holux Bluetooth GPS in conjunction with my PDA
> with MM. To safeguard the equipment I put both into my riucksack as
> getting into the Sea King is an ordeal for me :-)
>
> The GPS recorded the flight back to our car park, and after I placed the
> rucksack in the boot of my car, it also recorded the track back to
> Brecon from Torpantau.
>
> It was in contradiction of all the " good view of the sky" advice we
> get, I could hardly believe it.

The Holux probably has the more receptive SirfIII chipset GPSr.

I have a GPSr with that and it can get full lock indoors. The previous
one didn't and struggled to keep reception under any kind of leaf cover.

Paul Saunders

2007-08-24, 10:33 pm

Jack Erbes wrote:

> If you set it for time and one or two seconds, you'll not miss much if
> anything. You'll use up the track memory pretty quickly (2.78 hours?)

Too fast for me. Auto suits me best, because not only do I tend to make a
lot of twists and turns, but I also tend to stop frequently to take photos,
and I really don't want to log hundreds of trackpoints every time I stop to
take some photos.

> but if you're also logging the track to the memory card you'll not
> lose any data on trips that take more time than that.

Mine doesn't have a memory card. I'm using a Garming 60CS, what's yours?

>
> And was that with the Record Method set to time or distance? When I
> have it set to time, I get a spider web. With it set to distance, I
> do not.

Neither time nor distance, just plain auto, set to "most often".

> To see tracks that are accurate as far as time, distance, and path
> actually traveled, that is where I wind up in MapSource and editing
> the *.gpx files to remove superfluous track points, join track
> segments, and the like. Then when I look at the track properties I
> see time and distance values that are accurate.
>
> To see and get the statistics for portions of a longer track, I copy
> the track points and paste them into a new MapSource window.

I do all my editing in OxiExplorer. It's the first GPS software that I used,
and is still my favourite.

Paul
--
http://www.wilderness-wales.co.uk/
http://www.wilderness-wales.co.uk/weblog/

Bill Grey

2007-08-24, 10:33 pm

In message < 13ctjb08v12da02@news
.supernews.com>, willshak
<willshak@00hvc.rr.com> writes
>on 8/23/2007 3:37 PM Mike Coon said the following:
>
>A 'stationer' (with an E) is one that supplies book materials and
>writing materials, such as stationary (with an A).
>
>
>
Quite write !
--
Bill Grey

Bill Grey

2007-08-24, 10:33 pm

In message <10v4p7u5871or.dlg@uranus987.com>, Chris Game
<chrisgame@example.net> writes
>On Thu, 23 Aug 2007 22:55:15 +0100, Bill Grey wrote:
>
>
>How did it see through the boot lid?
>
>
Not being a GPS I wouldn't know - but it DID.

As I said before - I couldn't believe it at the time.
--
Bill Grey

Bill Grey

2007-08-24, 10:33 pm

In message < 0hktc3hlnjme6bgsr048
l71833h6mvoq92@4ax.com>, Alan White
<alan.lesley@ukgateway.net> writes
>On Thu, 23 Aug 2007 22:55:15 +0100, Bill Grey
><wdg@graigroad.demon.co.uk> wrote:
>
>
>We experienced this on Wednesday after I forgot to switch off my GPSmap
>60c. It was a bit irritating because the track log was quite important.
>
>The signal probably entered the car through the windows and went through
>the rear seat back into the boot.
>
Forgetting GPS for a while,

Nice to hear from you again Alan - how are things?

Best wishes
--
Bill Grey

Ian Rawlings

2007-08-24, 10:33 pm

On 2007-08-24, Bill Grey <wdg@graigroad.demon.co.uk> wrote:

> Quite write !

ITYM *quiet*, you alliterate..

--
Blast off and strike the evil Bydo empire!

Jack Erbes

2007-08-24, 10:33 pm

Paul Saunders wrote:
> Jack Erbes wrote:
>
>
> Too fast for me. Auto suits me best, because not only do I tend to make a
> lot of twists and turns, but I also tend to stop frequently to take photos,
> and I really don't want to log hundreds of trackpoints every time I stop to
> take some photos.
>
>
> Mine doesn't have a memory card. I'm using a Garming 60CS, what's yours?

Ahh, that explains it. I have a 76Cx so I have unlimited track data
storage as long as there is any free space on the microSD card. The
original post here was about a Vista HCx which does have a microSD card.

But, if the 60Cs is like the 76Cx, and if you wanted more track points
than you are getting on the Auto setting, choosing the Distance methods,
will stop the problem of track point collection when you are not moving.

>
> Neither time nor distance, just plain auto, set to "most often".

Okay, the settings and choices are different for the 60Cs then.

Jack

Phil Cook

2007-08-25, 7:33 am

Bill Grey wrote:

>In message <10v4p7u5871or.dlg@uranus987.com>, Chris Game
><chrisgame@example.net> writes
>Not being a GPS I wouldn't know - but it DID.
>
>As I said before - I couldn't believe it at the time.

Once those SirfIII types have a lock they are very reluctant to let
go.. My problem is that sometimes I want the thing to get a lock
whilst I am moving, sometimes I forget to switch it on when I'm in
in-car mode and it is rather hard to get a lock inside a central
London train station. I also discovered last week that the windows in
the Midland Mainline Meridian trains are impervious to satellite
signals :-(
--
Phil Cook, last hill: Angletarn Pikes via Beda Fell.
http://www.p-t-cook.freeserve.co.uk/May07/martin9.htm

Alan White

2007-08-25, 12:33 pm

On Fri, 24 Aug 2007 22:47:19 +0100, Bill Grey
<wdg@graigroad.demon.co.uk> wrote:

>Nice to hear from you again Alan - how are things?

Taken to e-mail ;-)

--
Alan White
Mozilla Firefox and Forte Agent.
Twenty-eight miles NW of Glasgow, overlooking Lochs Long and Goil in Argyll, Scotland.
Webcam and weather:- http://windycroft.gt-britain.co.uk/weather

Marcus Fox

2007-08-26, 10:33 pm

"Phil Cook" <u-r-walk@p-t-cook.freeserve.co.uk> wrote in message
news:5310d3po25mu44j
aaf8vf6u7li0dbrpdg9@
4ax.com...
> Bill Grey wrote:
>
>
> Once those SirfIII types have a lock they are very reluctant to let
> go.. My problem is that sometimes I want the thing to get a lock
> whilst I am moving, sometimes I forget to switch it on when I'm in
> in-car mode and it is rather hard to get a lock inside a central
> London train station. I also discovered last week that the windows in
> the Midland Mainline Meridian trains are impervious to satellite
> signals :-(

Are they? I'm sure I've had a signal when on one - Mio P550.

Marcus

Phil Cook

2007-08-27, 4:33 am

Marcus Fox wrote:

>"Phil Cook" <u-r-walk@p-t-cook.freeserve.co.uk> wrote in message
> news:5310d3po25mu44j
aaf8vf6u7li0dbrpdg9@
4ax.com...

>
>Are they? I'm sure I've had a signal when on one - Mio P550.

That's what I was using I never got any satellite signals to show up
on mine using OziCE. It was fine going north on the older HST but I
perhaps I gave up too soon in the Meridian. Still the 13 amp socket
was useful to charge the PDA battery.
--
Phil Cook, last hill: Angletarn Pikes via Beda Fell.
http://www.p-t-cook.freeserve.co.uk/May07/martin9.htm

BrianJ48@gmail.com

2007-09-03, 11:11 am

The Odometer / Trip Odometer on the Garmin eTrex Vista HCX seems
seriously flawed. Two hikes - one 6 miles - showed 2.4. One 4.1 miles
showed 2.6. Neither were under extreme condition - especially
considering the alleged "heavy tree cover" and "canyon" capabilities
we are promised.

Actual distances were accurate in tracks. As to "slow" walking - 1st
hike was 2 mph, 2nd at 1.6 mph.

Dominic Sexton

2007-09-03, 11:11 am

In message <1188767172.284036.289770@g4g2000hsf.googlegroups.com>,
BrianJ48@gmail.com writes
>The Odometer / Trip Odometer on the Garmin eTrex Vista HCX seems
>seriously flawed. Two hikes - one 6 miles - showed 2.4. One 4.1 miles
>showed 2.6. Neither were under extreme condition - especially
>considering the alleged "heavy tree cover" and "canyon" capabilities
>we are promised.
>
>Actual distances were accurate in tracks. As to "slow" walking - 1st
>hike was 2 mph, 2nd at 1.6 mph.
>

Other users have reported similar issues with this model. The more folk
who contact Garmin support about it the more likely they are to
acknowledge the issue and fix it in an update:

http://www.garmin.com/garmin/cms/si...supportcontacts
--
Dominic Sexton

BrianJ48@gmail.com

2007-09-03, 11:11 am

Dominic Sexton

2007-09-03, 11:11 am

BrianJ48@gmail.com

2007-09-03, 11:11 am

Dominic Sexton

2007-09-03, 11:11 am

Dan Anderson

2007-09-03, 3:33 pm

BrianJ48@gmail.com wrote:
> The Odometer / Trip Odometer on the Garmin eTrex Vista HCX seems
> seriously flawed. Two hikes - one 6 miles - showed 2.4. One 4.1 miles
> showed 2.6. Neither were under extreme condition - especially
> considering the alleged "heavy tree cover" and "canyon" capabilities
> we are promised.
>
> Actual distances were accurate in tracks. As to "slow" walking - 1st
> hike was 2 mph, 2nd at 1.6 mph.

1.6 mph is definitely too slow. One experiment I tried this
weekend was to walk fast and gradually slow down. I had a
76Cx in my other hand and watched the speed on both. When
I got below 2 mph on the 76Cx, the speed indication on the
Vista HCx was "stuck" at 2.1 mph. In other words the speed
wasn't dropping even though I was slowing down. It stayed
there until I actually stopped. The receiver indicated
2.1 mph on two tests and 1.7 mph on a third. In general,
the HCx doesn't indicate speeds less than 2 mph very
reliably.

There are filters (probably in the Mediatek chip) to
keep from accumulating noise and these are set too
high - a slow walk is seen as noise not actual movement.

The odometer worked just fine for a drive.

--
Dan
(email change 2001 to 2004)
(www.gpsmap.net)

peter

2007-09-03, 10:33 pm

On Sep 3, 11:06 am, Dan Anderson <danderson2...@hotmail.com> wrote:
> Brian...@gmail.com wrote:
>
>
> 1.6 mph is definitely too slow. One experiment I tried this
> weekend was to walk fast and gradually slow down. I had a
> 76Cx in my other hand and watched the speed on both. When
> I got below 2 mph on the 76Cx, the speed indication on the
> Vista HCx was "stuck" at 2.1 mph. In other words the speed
> wasn't dropping even though I was slowing down. It stayed
> there until I actually stopped. The receiver indicated
> 2.1 mph on two tests and 1.7 mph on a third. In general,
> the HCx doesn't indicate speeds less than 2 mph very
> reliably.
>
> There are filters (probably in the Mediatek chip) to
> keep from accumulating noise and these are set too
> high - a slow walk is seen as noise not actual movement.
>
> The odometer worked just fine for a drive.

This sounds just like the behavior of the early firmware of my Garmin
eMap (now almost 8 years old). There was a threshold speed of about
1.5 mph and below that speed the odometer wouldn't update. To get
decent estimates of distance while hiking I would use the "Save"
function for the tracklog for a snapshot of total miles to that
point.

This was fixed years ago in the eMap firmware so it's a bit
disappointing to hear that a similar problem exists in their newest
products. But I expect that Garmin will be fixing this in an upcoming
release, especially if they get enough complaints about it.

OldBill

2007-09-05, 3:33 pm

Check out static navigation.

Chris Malcolm

2007-09-11, 4:33 am

In uk.rec.walking Paul Saunders <pvs1@wildwales.fsnet.co.uk> wrote:
> Mick wrote:

[color=darkred]
> No, it's just that when you lose reception, or if you're walking
> particularly slowly, the odometer stops recording. On most of my walks the
> odometer and track distances are pretty similar, the difference is not
> enough to bother me. A big difference is usually down to bad reception, in
> which case I usually trust the track distance rather than the odometer, but
> it's important to check the track and delete the inevitable spurious points
> if that's the case. If a track is really messed up, it may be simpler to
> draw a new track over the top to find out the distance.

> Messed up tracks are in the minority though, in my experience. I usually get
> them in forested valleys, but most of my walks are in quite open ground so
> it's rarely a problem.

> As for the odometer speed threshold, below which it stops recording
> distance, it's 1.6kph (1mph) on both of the models I've owned. It may be
> different on other models, but I'd guess that all Garmins are set to that.
> It's easy to check, just walk slower and slower and watch the speed readout.
> As you drop below 1.6kph it suddenly reads 0kph, even though you're still
> moving.

On my Summit it's set to at least as low as 0.5mph. The reason I'm a
bit vague about it is that that's close enough to its minimum speed
that you have walk very smoothly and steadily at that speed for it to
consider that you're moving. Walking at an average speed of 0.5mph
with the usual slowing down and speeding up involved in a stride won't
do it. It samples speed sporadically, maybe once a second, and if it
happens to choose its sample at a point where your momentary speed was
slower than its threshold, it considers that to be stopped.

--
Chris Malcolm cam@infirmatics.ed.ac.uk DoD #205
IPAB, Informatics, JCMB, King's Buildings, Edinburgh, EH9 3JZ, UK
[http://www.dai.ed.ac.uk/homes/cam/]

Larry G

2007-09-11, 7:33 am

interesting discussion.

my take is that the difference is due to the unit not keeping hold of
the satellites all the time... and the "gaps" are connection by
straight lines vice the actual path.

but I would not expect this behavior from the better units (at
reception) like the 60/76 units... so would be interested in hearing
from owners of those units on this issue.

one thing I do not understand is that if a unit loses reception...
wouldn't it affect BOTH the odometer .. AND the track log?

the only thing the unit can do in either case is draw a straight line
between the previous point and the current point - right?

Paul Saunders

2007-09-12, 7:33 am

Larry G wrote:
> interesting discussion.
>
> my take is that the difference is due to the unit not keeping hold of
> the satellites all the time... and the "gaps" are connection by
> straight lines vice the actual path.

No, I'm pretty sure the odometer doesn't add the distance from the last
point. If it loses lock it simply stops recording, when it regains lock it
starts recording again, just the same as if you'd switched it off and back
on in a different place. That's why the odometer distance tends to be much
shorter than the track if reception has been bad.

> but I would not expect this behavior from the better units (at
> reception) like the 60/76 units...

Why not? Any model can lose reception. The better models may be better at
keeping lock, but just try walking into a cave with one! They can lose lock
in dense forestry too, and when you're scrambling up some rocks with the GPS
facing inward. Or even when you cover it with your arm when taking a
photograph!

> so would be interested in hearing
> from owners of those units on this issue.

I've got a 60CS. It's better than the eTrex models but it does lose lock
occasionally. The newer "x" models are supposed to be even better.

> one thing I do not understand is that if a unit loses reception...
> wouldn't it affect BOTH the odometer .. AND the track log?

Yes, but they affect it differently because they calculate the distance
differently.

> the only thing the unit can do in either case is draw a straight line
> between the previous point and the current point - right?

No, the odometer doesn't draw lines, only the track does that.

There are three things that can happen to the track when the reception gets
bad.

1. The unit starts to record inaccurate positions, so the track jumps about
and creates that infamous "spider's web" pattern. This increases the
distance.

2. If lock is lost temporarily, it continues recording and estimates where
you are. I think it does this for about 30 seconds or so. So it assumes that
you're travelling at the same speed and direction. I've tried walking into
my house doing this, then stopped and watched the GPS continue "moving"
through the walls and into the next house! It went quite a distance before
it stopped recording.

If the unit regains lock within this time period the position jumps to your
new position, so there's no break in the track. If you were walking at the
same speed and in the same direction, you probably won't even notice, but if
you changed direction there'll be a sudden erratic change in position, and
if you were twisting and turning, you'll just get a straight line, so the
distance could be longer or shorter, depending on what you were doing while
there was no signal.

3. If lock is lost for longer than that "grace" period, then it stops
recording, then starts again when it regains lock, so you get a gap in the
track. In this case the distance is shorter.

Of course, the advantage of recording a track is that you can study it later
on the computer and correct any obvious errors, i.e. get rid of the spiders
webs and the daft positions (where your walking speed was 150mph!) and
connect any missing bits of track. It won't be perfect, but a bit of editing
will give you a reasonably accurate result, probably moreso than trying to
measure it with a bit of string or a map measurer. But you can't do anything
about the odometer, so that's only really useful when you have good
reception throughout your walk, which is my case is most of them.

But every time I visit the Ystradfellte Falls I know I'm going to come back
with a screwed up mess!

Paul

Larry G

2007-09-12, 10:33 am

On Sep 12, 7:21 am, "Paul Saunders" <p...@wildwales.fsnet.co.uk>
wrote:
> Larry G wrote:
>
>
> No, I'm pretty sure the odometer doesn't add the distance from the last
> point. If it loses lock it simply stops recording, when it regains lock it
> starts recording again, just the same as if you'd switched it off and back
> on in a different place. That's why the odometer distance tends to be much
> shorter than the track if reception has been bad.
>
>
> Why not? Any model can lose reception. The better models may be better at
> keeping lock, but just try walking into a cave with one! They can lose lock
> in dense forestry too, and when you're scrambling up some rocks with the GPS
> facing inward. Or even when you cover it with your arm when taking a
> photograph!
>
>
> I've got a 60CS. It's better than the eTrex models but it does lose lock
> occasionally. The newer "x" models are supposed to be even better.
>
>
> Yes, but they affect it differently because they calculate the distance
> differently.
>
>
> No, the odometer doesn't draw lines, only the track does that.
>
> There are three things that can happen to the track when the reception gets
> bad.
>
> 1. The unit starts to record inaccurate positions, so the track jumps about
> and creates that infamous "spider's web" pattern. This increases the
> distance.
>
> 2. If lock is lost temporarily, it continues recording and estimates where
> you are. I think it does this for about 30 seconds or so. So it assumes that
> you're travelling at the same speed and direction. I've tried walking into
> my house doing this, then stopped and watched the GPS continue "moving"
> through the walls and into the next house! It went quite a distance before
> it stopped recording.
>
> If the unit regains lock within this time period the position jumps to your
> new position, so there's no break in the track. If you were walking at the
> same speed and in the same direction, you probably won't even notice, but if
> you changed direction there'll be a sudden erratic change in position, and
> if you were twisting and turning, you'll just get a straight line, so the
> distance could be longer or shorter, depending on what you were doing while
> there was no signal.
>
> 3. If lock is lost for longer than that "grace" period, then it stops
> recording, then starts again when it regains lock, so you get a gap in the
> track. In this case the distance is shorter.
>
> Of course, the advantage of recording a track is that you can study it later
> on the computer and correct any obvious errors, i.e. get rid of the spiders
> webs and the daft positions (where your walking speed was 150mph!) and
> connect any missing bits of track. It won't be perfect, but a bit of editing
> will give you a reasonably accurate result, probably moreso than trying to
> measure it with a bit of string or a map measurer. But you can't do anything
> about the odometer, so that's only really useful when you have good
> reception throughout your walk, which is my case is most of them.
>
> But every time I visit the Ystradfellte Falls I know I'm going to come back
> with a screwed up mess!
>
> Paul

good and useful discussion.

question: Is it correct to say that for a given scenario where a GPS
is used that the odometer will .. NEVER show a greater mileage than
actual... ???

.... will never show greater mileage than the track?

I have a 76csx and it is superb at keeping the lock... only once or
twice in fairly extreme conditions did it fail to keep the lock. It
will even lock on in the house if near a window...

I do have some experience with regard to a pre-drawn (transfered)
route from a PC to the unit... in terms of the route mileage ...
verses the odometer mileage.

in every case, so far, with the 76csx, the odometer mileage is greater
than the route.

The "routes" that I draw are down rivers.. where there are curves and
meanders.

Paul Saunders

2007-09-12, 10:33 am

Larry G wrote:

> question: Is it correct to say that for a given scenario where a GPS
> is used that the odometer will .. NEVER show a greater mileage than
> actual... ???

> ... will never show greater mileage than the track?

I don't think so, but to be honest I don't compare them very often. If
reception is good, I generally trust the odometer.

> I have a 76csx and it is superb at keeping the lock... only once or
> twice in fairly extreme conditions did it fail to keep the lock. It
> will even lock on in the house if near a window...

So I've heard. Sounds great.

> I do have some experience with regard to a pre-drawn (transfered)
> route from a PC to the unit... in terms of the route mileage ...
> verses the odometer mileage.
>
> in every case, so far, with the 76csx, the odometer mileage is greater
> than the route.
>
> The "routes" that I draw are down rivers.. where there are curves and
> meanders.

With routes you have a lot of straight lines between waypoints, even if the
waypoints are fairly close together, so you'd expect the actual distance to
be greater.

Paul

Nick

2007-09-23, 3:33 pm

I have a Zumo 550 and am staggered at how sensitive it is - It works easily
in the house even when not near a window and recently on two cross channel
ferry trips, it has had "full strength" indications even when seated near
the centre of the boat on deck 7 ( two down from top ) - my old GPS111 would
never work in such conditions and took ages to lock on even on a window
ledge.

LinkBot