[Openstreetmap] GPS track oddities

Jonathan McDowell noodles at earth.li
Fri Oct 14 18:12:32 BST 2005


I've been trying to produce some tracks around Norwich, but have been
having problems with my tracks appearing out compared to the Landsat
maps. At first I thought this was due to my cheap USB GPS receiver, but
I tried with a Magellan hand held device as well with similar problems.

So I tried something else. I used Streetmap to look up co-ordinates of a
roundabout (52.645225 1.276237) and a bit further up that road
(52.645992 1.273559).

Looking at the points with Google Maps shows them as you'd expect:

http://maps.google.co.uk/maps?q=52.645225+1.276237&iwloc=A&hl=en
http://maps.google.co.uk/maps?q=52.645992+1.273559&iwloc=A&hl=en

So I created a GPX file with these 2 points in it:

<gpx version="1.0" creator="A quick Perl hack"
	xmlns="http://www.topografix.com/GPX/1/0">
<trk>
<trkseg>
<trkpt lat="52.645225" lon="1.276237">
<time>2005-10-14T17:40:02Z</time>
</trkpt>
<trkpt lat="52.645992" lon="1.273559">
<time>2005-10-14T17:41:02Z</time>
</trkpt>
</trkseg>
</trk>
</gpx>

and fed this into osm-editor. Tell it to pull the Landsat data and I get
an image like:

http://the.earth.li/~noodles/osm-wrong.png

(248k)

This seems to me that I'm not going insane and that there's something
wrong with either the LandSat data or the way osm-editor and OSM deal
with it. Can anyone shed any light on this?

J.

-- 
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