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[DPRG] Further Quandries on GPS...
Subject: [DPRG] Further Quandries on GPS...
From: Kenneth Maxon
kmaxon at qwest.net
Date: Tue Jan 1 21:18:40 CST 2008
Hello DPRG...
Here is one for further conversation in the "Hmmm...?" realm...
It was up to a fair 8-deg today and although there is a significant snow
pack on the ground the sun was bright and the sky was clear for a few hours
so ProtoBot ventured back out into the back yard for more GPS expiremental
data gathering.
This time I made sure that ProtoBot was a full 12 ft away from the house and
this time, the house does not have a 1/2"~3/4" glaze of ice hanging on it.
There is however a 3/4" layer of solid ice under the snow back that ProtoBot
is sitting on. I pulled a bonehead move and forgot to take my hand held
Garmin + adapter & extension cord out to verify the readings, however,
surprisingly ProtoBot still recorded erronous readings, like it was doing
inside and in the previous outdoor trial up along side the house.
I have taken time to swap out the GPS module / antenna combination on
ProtoBot with the spare unit that I'll be using on an upcoming project. And
given that ProtoBot's last round of testing performed in a similar (although
less drastic from an error standpoint) manner than did the comercial Garmin
unit, I still have a quandry here. Yes, I am still wondering *IF* this
could be coming from multipath off of the ice layer. I theroise that it is
not as the 10" of snow pack sitting on top of the ice should be enough to
completely disburse the energy, and all of the sattelites reported by the
module as being used in the actual position calculation had a good signal
strength reading.
I don't know that anyone on this list will have input, however it is an
interesting quandry that I am working through and I thought it might be of
interest to the group, as there are others in this group that activly use
GPS on their robots.
Of course I'll post futher when I get to the bottom of the
ssue... -Kenneth
BTW, Ron, the package arrived, thank you. You didn't have to return it but
since you did I'll put it to good use in the next project. (IE, you've
saved me from some eBay surfing). -Thanks...
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