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Cellular forums Home > Archive > GPS > June 2006 > GPSmap60CSx: difference in length of track and trip
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GPSmap60CSx: difference in length of track and trip
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| hermans 2006-06-29, 7:34 am |
| I registered a track during a walk and afterwards I stored this track.
The active log has 1198 points and the total length is 28.20km.
The stored track counts 500 points and the total length is 27.70km. This
difference is acceptable. But: the trip odometer mentions only 25.60km.
For the walk I made, I think the odometer gives the most realistic result.
But the difference between the results of the odometer and the track
seems quite big.
Looking at the tracks using OziExplorer I notice there quite often
occurs a kind of web at some points : the GPS seems to be confused
(reflected signals?) and so the total distance increases.
Is there a possibility to obtain a better result for the track using
other settings than "auto" (time - distance)?
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| Graydon 2006-06-29, 7:34 am |
| Some things I've noticed.
While standing still, the GPS unit racks up distance, just from
positional errors; this can be as much as 100 meters per minute!
Solution: Clear your track logs and reset your odometer before
actually leaving. If you reset one, and not the other, there will be
difference in travel distance.
When you SAVE a log it reduces the number of track points and does
some averaging of the path, this will decrease the actual track
distance form the original log.
Solution: Don't save track logs with the expectation to use them as an
accurate representation of your trip.
On Tue, 27 Jun 2006 08:42:05 GMT, hermans <sasse1@telenet.be> wrote:
>I registered a track during a walk and afterwards I stored this track.
>The active log has 1198 points and the total length is 28.20km....
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| hermans 2006-06-29, 7:34 am |
| Graydon schreef:
> Some things I've noticed.
>
> While standing still, the GPS unit racks up distance, just from
> positional errors; this can be as much as 100 meters per minute!
> Solution: Clear your track logs and reset your odometer before
> actually leaving. If you reset one, and not the other, there will be
> difference in travel distance.
Before I started I had cleared both. As I wrote I noticed positional
errors while viewing the track in Oziexplorer. But I don't understand
why taking into account these positional errors the measured distance
for the track and the trip (the odometer) differ so much.
I didn't have such a big difference using the GPSMAP76S. Perhaps the
receiver of the 60CSx is too sensible (reflected signals).[color=darkred]
>
> When you SAVE a log it reduces the number of track points and does
> some averaging of the path, this will decrease the actual track
> distance form the original log.
> Solution: Don't save track logs with the expectation to use them as an
> accurate representation of your trip.
>
>
> On Tue, 27 Jun 2006 08:42:05 GMT, hermans <sasse1@telenet.be> wrote:
>
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| James B. Thies 2006-06-29, 7:34 am |
| I have the same experience with my ETrex Legend. I find that when I walk a
fairly straight course at a good, steady pace, the odometer and track log
distances are in close agreement. But when I stop and go with many changes
in direction and perhaps pauses to take pictures etc., then the track log
distance is consistently longer than the odometer distance. On the one had,
I would expect the track log distance to be shorter since it is a summation
of straight line segments. But apparently what is actually happening is that
the odometer algorithm is filtering out "random" movements when I pause or
mill around in order to avoid accumulating measurement errors while standing
still. This filtering algorithm works quite satisfactory when you are in
continuous motion, but tends to "over filter" when you pause and change
direction a lot. On a typical forest hike on rough terrain, I get odometer
readings 5 to 15 percent lower than the track log distances. But when I do a
continuous "exercise" walk on a clear sidewalk or track, the odometer and
track log distances are virtually identical.
"hermans" <sasse1@telenet.be> wrote in message
news:xb6og.505609$w52.12555370@phobos.telenet-ops.be...
>I registered a track during a walk and afterwards I stored this track.
> The active log has 1198 points and the total length is 28.20km.
> The stored track counts 500 points and the total length is 27.70km. This
> difference is acceptable. But: the trip odometer mentions only 25.60km.
> For the walk I made, I think the odometer gives the most realistic result.
> But the difference between the results of the odometer and the track seems
> quite big.
> Looking at the tracks using OziExplorer I notice there quite often occurs
> a kind of web at some points : the GPS seems to be confused (reflected
> signals?) and so the total distance increases.
> Is there a possibility to obtain a better result for the track using other
> settings than "auto" (time - distance)?
| |
| hermans 2006-06-29, 7:34 am |
| James B. Thies schreef:
> I have the same experience with my ETrex Legend. I find that when I walk a
> fairly straight course at a good, steady pace, the odometer and track log
> distances are in close agreement. But when I stop and go with many changes
> in direction and perhaps pauses to take pictures etc., then the track log
> distance is consistently longer than the odometer distance. On the one had,
> I would expect the track log distance to be shorter since it is a summation
> of straight line segments. But apparently what is actually happening is that
> the odometer algorithm is filtering out "random" movements when I pause or
> mill around in order to avoid accumulating measurement errors while standing
> still. This filtering algorithm works quite satisfactory when you are in
> continuous motion, but tends to "over filter" when you pause and change
> direction a lot. On a typical forest hike on rough terrain, I get odometer
> readings 5 to 15 percent lower than the track log distances. But when I do a
> continuous "exercise" walk on a clear sidewalk or track, the odometer and
> track log distances are virtually identical.
Viewing the track using a program such as oziexplorer I find there are a
lot of random movements that increase the length of the track (about
10%). I can put an image available. I think the distance measured by the
odometer is more close to the real distance I walked. Perhaps Garmin
should try to ameloriate the filtering: I didn't encounter this problem
with my 76CS.
>
> "hermans" <sasse1@telenet.be> wrote in message
> news:xb6og.505609$w52.12555370@phobos.telenet-ops.be...
>
>
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