[Openstreetmap-dev] Landsat update

Jo Walsh jo at frot.org
Sat Apr 30 11:26:57 BST 2005


On Sat, Apr 30, 2005 at 11:05:31AM +0100, Nick Whitelegg wrote:
> http://www.free-map.org.uk/downloads/landsat_demo.png
> There must be, however, some sort of projection issue. The coastal path is 
> slightly in the water! The tracks were surveyed with a Garmin GPS while the 
> Landsat data is from the NASA server, so at a guess, the Garmin is programmed 
> to use the UK projection while the NASA server the standard worldwide 
> projection?

if you save one of the NASA files and run 'gdalinfo' on it, it should
show the projection near the top. Nng, i suppose that NASA reprojects
them into UTM, probably zone 30 or 31? 

gdal_translate lets you shift a raster from one projection to another
- the UK projection is istr epsg:27700 but i wonder if this is really
  your issue - we tend to have our Garmin set to WGS84

k, i see in grab_landsat.c that you're requesting the landsat tiles in
WGS84. (EPSG:4326). if both your data sets are in WGS84 then perhaps
it's only a GPS accuracy problem - how far into the sea are your
points?

i *think* you can request a different on-the-fly reprojection from a
WMS - try EPSG:32630 which i am using for most things UK map related.
Images appear vertically squashed to me otherwise... i don't know how
this would impinge on your backend tho


zx






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