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[aprssig] Aerial Photos (Terraserver) and findU

Steve Dimse k4hg at tapr.org
Sun Nov 14 06:01:37 UTC 2004


I was finally able to lay off the pain pills long enough to get some work done!

Here is a script to grab Terraserver tiles and return an image with a geo file.
This works as other geo file cgi's I've done, the cgi returns the geo file, the
image is placed in a temp file referenced by the geo file. And as with other geo
scripts, this can be used in any cgi with a geo parameter. For example:

http://www.findu.com/cgi-bin/plot.cgi?call=*&geo=http://mm.aprs.net/terra.cgi?
call=k4hg|scale=1

The center of the image (and in this case it means the point occurs in the
center tile, not at the exact center of the image) is specified wither with a
callsign or a lat/lon pair:

http://www.findu.com/cgi-bin/plot.cgi?call=*&geo=http://mm.aprs.net/terra.cgi?
lat=24.67|lon=-81.5|scale=64

scale is meters-per-pixel, values accepted by terraserver are 1, 2, 4, 8, 16,
32, and 64.

So far this only returns a 600x600 image, I'll be expanding it to make it work
at other sizes.

The tiles are cached on findU, so the first time you load a particular lat/lon
and scale, it will take longer (about 8 seconds), after that it only takes a a
second to render the map. At some point I'll have to start pruning the cache
based on the last time a tile was used, but of course after the first reload it
again will be in the cache.

Please give this a good workout and let me know how it works...

Steve K4HG




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