[Geowanking] Web-based Map Rectification
crschmidt at metacarta.com
Sun Oct 8 15:11:50 PDT 2006
On Sun, Oct 08, 2006 at 11:42:37PM +0200, Sam Critchley - A2B.cc wrote:
> Very interesting. Maybe I don't get it, and this is already being done, but is there a way to store the X/Y to long/lat mappings in the EXIF header of a JPEG somehow after you've warped the image, then you could use the image as a raster map in moving-map applications? I think a couple of more affordable GPS navigation applications do this kind of thing already and it would help with map availability.
After you've warped an image, there is a link available to download the
georeferenced image. If you look at a map page for an image which has
been warped, you'll see a 'download warped image' option.
This 'warped image' is a GeoTIFF: GeoTIFF is the best format that we
could come up with to deliver the image and its metadata in one file.
There are other ways of storing the metadata: with JPEGs, I believe a
wsecond file is stored, known as a 'world file'. This file will allow
you to open your images in a geospatial application.
We chose to support GeoTIFF since it seemed that storing the metadata
directly in the image was the best way to make the files available, as
well as providing a WMS URL that could be used directly by any software
which understands WMS. JPEG files do not have a way to store
georeferencing information directly inside the image, as far as I
understand it, which is why we went with GeoTIFF.
I have successfully downloaded, dragged and dropped a GeoTIFF generated
by this service into osgPlanet via OSSIM, and downloaded the image and
dropped it into being served via MapServer, with no problems. If there
is another format that you would find more useful, we will gladly work
to provide that format: providing a use case so that we can make sure to
test it in that software to ensure it works.
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