etrex Summit error mystery

Anyone got any ideas on what might be the problem, or at least why?? ...
it's a Garmin Etrex Summit, bought new about 6 weeks ago.

Several times I've been out on rides where I wanted to capture the actual
route with the Track feature. So, cleared the Track memory and made sure
that all satellites had been found before moving off (obviously did that
outdoors).

At the cafe stop about half way through the ride (c 20 mins stop) - first
time I left the machine switched on, outdoors on the bars of the bike -
second time switched off the machine and then switched back on, located
satellites and then moved off.

In both cases the Track when imported to Memory Map showed a pair of long
track lines, dead straight, at an almost right angle to the actual track at
the cafe stop point.

Very strange! ... especially as the second time the Track distance recorded
and transferred said it was 6,200 km ! (the whole ride was about 45km)

All suggestions gratefully received

Hi not exactly sure why these things happen, but they used to bug me
too. I now let the GPS find and lock on to satellites before clearing
track memory and during stops I found its best to leave GPS switched on
and in a good position to recieve a signal, this seems to almost "cure"
these problems. The spikes you mentioned in MM can easily be removed:
just right click on the spike and select "Remove velocity spike" hope
this has been of some help.


RG wrote:

RG wrote:


Its an error caused by mis-seeing the satelites. It can happen almost
anywhere, so you need to be aware that it can happen.

Main causes:

"canyons" - area where there are tall features alongside you (buildings,
deep valleys) meaning you cannot see enough/any satellites
"reflections" - caused by being alongside a building or other big object
which can reflect a satellite signal
"tree cover" - too much overhead stopping a good view of satellites.
Rain/cloud can make this worse. Your body can be a partial screen of the sky
if the GPS is below you.
"body absorption/reflections" - GPS beside person, causes any of the above.
"aerial wrong way" - Etrex have the aerial such that the unit works best
when horizontal, screen uppermost, other positions give less good reception,
though generally still works.
"faulty GPS satellite" - rare, but must be possible, so position goes wrong


There is nothing wrong with the Etrex from the report you have above, its
perfectly normal. Inspect your track log when home, and remove the
evidently random track points.

Probably easier to not switch the GPS off in the middle of a recording; just
carry it into the cafe, it will loose track of satellites (probably report
that on screen), then will re-gain them when you get outside again.



- Nigel





--
Nigel Cliffe,
Webmaster at http://www.2mm.org.uk/

RG wrote:


I had a similar experience today, walking near Megget Reservoir. GPS
functioned perfectly all day, with one exception. A plane flew
overhead, at fairly low altitude, and I lost satellite coverage. It
recovered less than a minute later, but tracklog showed 2 waypoints at
right angles to route I was following, implying I'd walked about 2
miles in 30 seconds. It seemed fairly certain that the plane had caused
the blip - possibly a military plane scrambling the signal?

Bernie

agentmancuso wrote:
Nigel is right about carrying it into the café, otherwise you may find
yourself with no problems, 'cus you have no extex!