[OSM-newbies] Will the real track please step forward
Dirk-Lüder Kreie
osm-list at deelkar.net
Mon Mar 26 00:06:08 BST 2007
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digger vermont schrieb:
> I have a few tracks I've made by walking around. They make me look like
> a drunken sailor with the amazing ability to right through blocks of
> buildings! I've another from driving that looks somewhat better. It
> actually coincides for the most part with yahoo maps. Is this as good as
> it gets?
>
> I have made some nodes, segments, and ways but at this point I hesitate
> to upload them because of the accuracy.
The SirfStar III Chipset has problems in some situations when you walk
with it, because it trusts speed measurements more than position
measurements apparently.
Disclaimer: I have no real knowledge about how the SirfStar III does
stuff internally, this is based solely upon my own observations of the
behaviour and some knowledge about GPS measurements in general.
Due to the nature of the sampling inside the GPS receiver it detects the
diverse movements of the walking body and extrapolates its next
positions from it, when the positional data is not accurate enough (only
3 sats or bad reception) it even "drifts" in that direction for a bit
longer than strictly needed, thus generating these "drunken sailor" tracks.
You'll find that putting the GPS receiver on your back or shoulder and
cycling to be much more accurate than walking, because the speed
measurements and the repeated location samples can work together.
Dirk-Lüder "Deelkar" Kreie
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