Fawcett, David wrote:
Did you go with CGI or MapScript? Care to share a snippet?
Still, here are all the steps in one place. Hopefully this will get
archived and spidered, and the next Google user will have an easier time
than I did! (though a missing - sign in my coords was the true culprit
in many of my tribulations)
I used Mapserver's built-in CGI query mechanism, as it provides
sufficient abstraction to automagically convert latlon and layer into a
image file and pixel, even crossing tileindexes. That would've been 90%
of the hard stuff, done already!
The mapfile does need a query template for the raster layer, as is
documented:
LAYER
NAME "avhrr"
STATUS on
TYPE raster
DATA "AVHRR_SST/avhrr-today.tif"
TEMPLATE "/maps/wms/pixel.template.html"
END
And pixel.template.html is simply this one word, the raw pixel value
from whatever point was selected, from band 0.
[value_0]
The query was intended, as you can see, for a given latlon as opposed to
a point-click and pixels within an image of known height. And since this
was within PHP, I really did want to use 'localhost'
http://localhost/cgi-bin/mapserv?map=/maps/wms/sst.map&mode=query&layers=%s&mapxy=%f+%f
Now in PHP, I simply do file_get_contents($url) and I have the raw pixel
value. In many cases, the pixel value is not the same as the desired
data value but that conversion varies with your particular dataset.
--
Gregor Mosheh / Greg Allensworth, BS, A+
System Administrator
HostGIS cartographic development & hosting services
http://www.HostGIS.com/
"Remember that no one cares if you can back up,
only if you can restore." - AMANDA
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