Walk through the woods

[stephanpls]

What we all know is that GPS reception decreases in (dense) woods. I wanted to make a little study about that and put that fact in a map. So I taped my Gilsson on my right shoulder, put the connected iQue in my pocket and made a 3.5 km walk through the woods close to my home. I logged the track not only with QueTracks, but also with CetusGPS with a 10 sec interval. In the Cetus logfile the number of tracked satellites is stored also. After some data processing I imported the Cetus file in Mapinfo and made a map with the number of tracked satellites as thema. The background is the Dutch topo map 1:50000 in raster. In the legend the figures beside the colour mean the number of tracked satellites, between parentheses the number of times that that value occurred during the walk.

It expectedly shows that in the green area (woods), especially in the upper part, the number of satellites is generally lower than in open area (not green) where the number is almost constantly nine. Anyway, even in dense woods the satellite reception is better that I expected, the iQue almost always manages to make a satisfactory fix, and many times with more than sufficient satellites. Only a few times there was no fix at all (zero satellites tracked).

[Curious Cat]

Very interesting! Were any of the leaves wet from rain or dew?

[stephanpls]

No. Finally the summer seems to arrive here. It was sunny and no wet or moist leaves.

[jonasolof]

Very nice test!

I'm also curious about another related thing. If you could find a straight path in a dense forest and walk along it, it would be interesting to see how straight the resulting track would be in high resolution.

I assume that there isn't any averaging done for the 10 second Cetus positions.

One reason I ask is that I have been asked to help to find a property limit along 2 kilometers in a dense forest. We know the start and end points but need to mark the property boundary again. I don'ttnik EGNOS will work in the forest but I'm thinking of using coast guard longwave differential correction instead (with a Magellan marine handheld NAV6000). I know there are other sources for more precise terrestrial positioning, but I don't have access to those professional grade survey techniques.

[kenspice]

Hi, Jonas, I may be off base here so ignore it if it does not help.
If you know the start and stop points, why not make waypoints in both places then turn on your course line and point it (while standing on the start point) at the finish point. Then make more way points on that line. I say use the course line because it is much thinner than the "route to" line and therefore more accurate. Hope this helps but I am fairly sure you have already thought of it.