| Extracting raster using Shapefile as ROI -Revisited [message #52216] |
Thu, 11 January 2007 18:20 |
Gaurav
Messages: 50
Registered: January 2007
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Hi everyone,
I am using IDL to make a customized Remote Sensing and GIS application
wherein I open georefernced satellite image tiles (like ETM -200 tiles,
each of which are 10000 by 10000 pixels in size) over a basic globe
skeleton-like the one defined by d_map.pro in the demo program for
mapping. And this part is easily done with a few hitches.
Next, I want to create subsets if these images, the boundaries of these
subsets being defined by the nodes of a particular shapefile polygon.
Displaying the shapefile or getting the nodes is not too difficult a
job too and I did it using objects. Now, I could easily convert these
nodes to device coordinates and use POLYFILLV to extract the desired
portion (as David very kindly suggested) but this would pose a minor
hitch. That way, I have to have the whole of the portion under the
polygon in display and so I have to CONGRID it or, as it is now,
display them as small tiles using MAP_IMAGE. Using POLYFILLV would only
give me this highly reduced image as output, something that I do not
desire. I want portions of the original image cut out according to the
shapefile.
I found a link in the group:
http://groups.google.com/group/comp.lang.idl-pvwave/browse_t hread/thread/4b90c8f4a2c7b715/6e29cac0ee6fe976?q=Apply+a+sha pefile+to+raster+images+in+IDL&rnum=1#6e29cac0ee6fe976
But I am not sure how it could help me too.
Please bail me out of this problem. I do not exactly need codes, just a
few suggestive pointers or algorithms would do the trick for me.
Regards,
Gaurav
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