Garmin E Trex reading



T

Trevor

Guest
On our walk today my mate measured with his map wheel to 5.5 mls. I
measured it with my normal thumb length for half a mile and it came to 5.5
to 6 mls, and the E Trex gave 7.1 miles. Why should this be? It also gave
our moving average as 4 mph which seemed too high as well.
 
Bitstring <[email protected]>, from the
wonderful person Trevor <[email protected]> said
>On our walk today my mate measured with his map wheel to 5.5 mls. I
>measured it with my normal thumb length for half a mile and it came to 5.5
>to 6 mls, and the E Trex gave 7.1 miles. Why should this be? It also gave
>our moving average as 4 mph which seemed too high as well.

Load the trackpoints from the etrex into something (Oziexplorer,
mapsource, whatever) and you will probably find some 'whacky' points
(especially near the start). Delete those and you'll get a saner answer.
The etrex is (in)famous for sticking in unbelievable points when it gets
marginal lock (you really need to work to hold it with the antenna
facing up, all the time).

The more expensive 60C, and especially the 60Cx models, don't have that
problem.

--
GSV Three Minds in a Can
9,423 Km walked. 1,827Km PROWs surveyed. 33.2% complete.
 
Trevor wrote:
> On our walk today my mate measured with his map wheel to 5.5 mls. I
> measured it with my normal thumb length for half a mile and it came
> to 5.5 to 6 mls, and the E Trex gave 7.1 miles. Why should this be?

Have you checked the track on the map? It may be because of bad reception
and spurious points (spider webs), but if not, then it's probably because
all the little twists and turns you did added up to a lot more than you
realised. That's why I've always said that a GPS is great for finding out
where you really went as opposed to where you thought you went (which is no
doubt what your mate measured with his map wheel).

> It also gave our moving average as 4 mph which seemed too high as
> well.

It does sound a bit high, so maybe bad reception was the problem. Try
removing any spurious points from the track and see what distance you end up
with then.

Paul
 
"Paul Saunders" <[email protected]> wrote in message
news:[email protected]...
> Trevor wrote:
>> On our walk today my mate measured with his map wheel to 5.5 mls. I
>> measured it with my normal thumb length for half a mile and it came
>> to 5.5 to 6 mls, and the E Trex gave 7.1 miles. Why should this be?
>
> Have you checked the track on the map? It may be because of bad reception
> and spurious points (spider webs), but if not, then it's probably because
> all the little twists and turns you did added up to a lot more than you
> realised. That's why I've always said that a GPS is great for finding out
> where you really went as opposed to where you thought you went (which is
> no doubt what your mate measured with his map wheel).
>
>> It also gave our moving average as 4 mph which seemed too high as
>> well.
>
> It does sound a bit high, so maybe bad reception was the problem. Try
> removing any spurious points from the track and see what distance you end
> up with then.
>
> Paul

Not sure how I know which points are spurious, when I don't have a map in
the screen??

>
 
Bitstring <[email protected]>, from the
wonderful person Trevor <[email protected]> said
>
>"Paul Saunders" <[email protected]> wrote in message
>news:[email protected]...
>> Trevor wrote:
>>> On our walk today my mate measured with his map wheel to 5.5 mls. I
>>> measured it with my normal thumb length for half a mile and it came
>>> to 5.5 to 6 mls, and the E Trex gave 7.1 miles. Why should this be?
>>
>> Have you checked the track on the map? It may be because of bad reception
>> and spurious points (spider webs), but if not, then it's probably because
>> all the little twists and turns you did added up to a lot more than you
>> realised. That's why I've always said that a GPS is great for finding out
>> where you really went as opposed to where you thought you went (which is
>> no doubt what your mate measured with his map wheel).
>>
>>> It also gave our moving average as 4 mph which seemed too high as
>>> well.
>>
>> It does sound a bit high, so maybe bad reception was the problem. Try
>> removing any spurious points from the track and see what distance you end
>> up with then.
>>
>> Paul
>
>Not sure how I know which points are spurious, when I don't have a map in
>the screen??

Any point where you suddenly leap 100m from the last point, and then
shortly after leap back. If you load the track into oziexplorer or
mapsource it is usually pretty obvious, even without an underlying map.

Dud points will likely have stupid height and velocity values attached
too.

--
GSV Three Minds in a Can
9,423 Km walked. 1,827Km PROWs surveyed. 33.2% complete.
 
On Sep 2, 9:12 pm, "Trevor" <[email protected]>
wrote:
> On our walk today my mate measured with his map wheel to 5.5 mls. I
> measured it with my normal thumb length for half a mile and it came to 5.5
> to 6 mls, and the E Trex gave 7.1 miles. Why should this be? It also gave
> our moving average as 4 mph which seemed too high as well.

On my basic yellow Etrex I find turning off Battery Save gets rid of
'all' the spikes.

As has been mentioned the GPS will record where it has been, not where
you think it has been, plus if it looses its signal it wil draw a
straight line from the last known point.

So if you walk around taking a few photographs whilst carrying the GPS
that distance is logged, e.g. if I carry mine whilst cutting my small
lawn, it says I have walked about 0.5 miles, just walking up and down
the lawn.

Also the distance displayed by any 3rd party software could have spike
removal turned on, e.g. if you are walking and the speed you reached
the next GPS point was over say 10 mph than that is probably a spike
and can be removed, unless of course you have just jumped off a cliff!

Ted
 
The message <[email protected]>
from "Trevor" <[email protected]> contains these words:


> Does this cable have any generic name or is it a yellow garmin etrex to pc
> cable?


I think you'll find that it is a Garmin generic to serial - and,
inevitably there is now a newer version of Garmin serial, as used on the
60CSX.

It is also possible that you might be better off with the Garmin serial
to USB with dongle and driver, given that few modern lap tops have a
serial connexion. Memory-Map do one.

Otherwise try googling & you'll find several providers.

Richard
 
In article <[email protected]>, Richard Spencer
<[email protected]> writes
>The message <[email protected]>
>from "Trevor" <[email protected]> contains these words:
>
>
>> Does this cable have any generic name or is it a yellow garmin etrex to pc
>> cable?

It will most likely be referred to as an eTrex or eMap cable.

The turquoise table near the top of this page lists their cables
available for the eTrex.

http://www.lynks.co.uk/cables.html

They are an excellent supplier with reasonable prices. You may be able
to find cheaper on eBay.
>
>I think you'll find that it is a Garmin generic to serial - and,
>inevitably there is now a newer version of Garmin serial, as used on the
>60CSX.

In fact that one is a resurrection the older one as used with the early
Garmin GPS receivers (38, 40, 45, 12, II, II+ etc.)
>
>It is also possible that you might be better off with the Garmin serial
>to USB with dongle and driver, given that few modern lap tops have a
>serial connexion. Memory-Map do one.

Lynks also do a USB - RS-232 converter if it is needed. Not as cheap as
some but if I was after one I would probably buy from them.

--

Dominic Sexton
 
ted <[email protected]> wrote:
> On Sep 2, 9:12 pm, "Trevor" <[email protected]>
> wrote:
>> On our walk today my mate measured with his map wheel to 5.5 mls. I
>> measured it with my normal thumb length for half a mile and it came to 5.5
>> to 6 mls, and the E Trex gave 7.1 miles. Why should this be? It also gave
>> our moving average as 4 mph which seemed too high as well.

> On my basic yellow Etrex I find turning off Battery Save gets rid of
> 'all' the spikes.

Whereas on mine it merely removes most of them :) There's almost
always a few at switch on, for example, and not infrequently one or
two when recovering lock after a lost lock episode.

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