Georeference a satellite imageFirst, you need an image, and a lat/lng footprintSo we'll start with a jpeg containing an ASAR image ASA_WSM_1PNPDK20110831_161028_000002693106_00112_49695_3285.N1_4E5EC73B_image_0150.jpg And the lat/lng of the 4 corners of the image -92.246384,32.628281 -87.924263,31.908293 -95.477028,16.658155 -91.673897,15.906074 use gdalinfo to get the dimensions of the original image gdalinfo ASA_WSM_1PNPDK20110831_161028_000002693106_00112_49695_3285.N1_4E5EC73B_image_0150.jpg Driver: JPEG/JPEG JFIF Files: ASA_WSM_1PNPDK20110831_161028_000002693106_00112_49695_3285.N1_4E5EC73B_image_0150.jpg Size is 5532, 23760 Coordinate System is `' Image Structure Metadata: SOURCE_COLOR_SPACE=YCbCr INTERLEAVE=PIXEL COMPRESSION=JPEG Corner Coordinates: Upper Left ( 0.0, 0.0) Lower Left ( 0.0,23760.0) Upper Right ( 5532.0, 0.0) Lower Right ( 5532.0,23760.0) Center ( 2766.0,11880.0) Band 1 Block=5532x1 Type=Byte, ColorInterp=Red Image Structure Metadata: COMPRESSION=JPEG Band 2 Block=5532x1 Type=Byte, ColorInterp=Green Image Structure Metadata: COMPRESSION=JPEG Band 3 Block=5532x1 Type=Byte, ColorInterp=Blue Image Structure Metadata: COMPRESSION=JPEG The first thing to do create a temporary tiff with GCPs (Ground Control Points) that map each corner of the image to a lat/lng pair. We also set the projection to ESPG:4326 which is what Google Earth uses gdal_translate -a_srs EPSG:4326 \ xlate_temp.tif Next we run gdalwarp to create the geo-referenced tiff with "north up". It makes a squared up image by adding buffer space around the original image. gdalwarp -tps xlate_temp.tif georeferenced.tif At this point you should be able to load georeferenced.tif into Google Earth as an image overlay, and the original image should appear within the footprint If the image is really big and you want to make a smaller version for testing, add -ts and set a width for the final image. Leave the height set to 0 and gdalwarp will compute it based on the width gdalwarp -ts 2000 0 -tps xlate_temp.tif georeferenced.tif If you want to set the nodata color for the buffer that is created around the original image, use -dstnodata. This will set the buffer area to white: gdalwarp -dstnodata "255 255 255" 0 -tps xlate_temp.tif georeferenced.tif Other Referenceshttp://code.google.com/apis/kml/articles/raster.html |
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