Projection, QUAC – ENVI – Harris Geospatial Solutions
When I load it to Envi, the image seems like it has no projection (has the shape of a rectangle, but it should be a parallelogram). When I load it to ArcMap, picture has projection (WGS 84, UTM 33N). But if I something change in ENVI (format or calculate some index) and then I save the picture as tiff/geotiff, than the picture lose projection (in ArcMap). I want open this file in ArcMap, but than show me some warning, that me picture has no projection. I need help, how to say to ENVI, that my picture has this projection. I try button Map – Convert Map projection, but it has no effect for me (just create some txt file, but picture stays without projection). I have next problem with QUAC. I need make atmospheric corrections (for this SPOT), but when I run QUAC and choose my image, than show me warning : The input file must contain valid wavelenghts. But I dont know whats the problem. I dont understand what is meant as VALID wavelenghts. Does your SPOT image come with an ancillary file with a .dim extension? If so, then open your file as SPOT DIMAP format using File ->,Open External File ->,SPOT->, DIMAP. This will automatically assign the appropriate wavelengths to the bands. Otherwise, ENVI will open the file as generic TIFF. Next, you can check if ENVI sees the map projection by looking in the Available Bands List to see if the file has a little Globe icon with a ‘+’ symbol next to it that says ‘Map Info’. If you click on the +, it should show you the map projection. What does it say for a map projection? Does it show it is in UTM projection? If so, then ENVI sees the map projection fine. This map information should be passed on with the file through any processing and you can confirm this by looking at the Map Info in the Available Bands List. If you are running ArcGIS 9.3 or 10, you do not need to export the file to TIFF to open the file in Arc. Arc will automatically recognize an ENVI format file with a .dat or .img extension so you can open it directly in Arc and the Map Information should be passed along with the file. Thank you. I found SPOT as DIMAP format. When I load it and roll Map Info, I see the right projection. I stil have problem with ArcGIS 9.3. If I make for example NDVI from me image, it has stil the right projection. But if I use automatic opening in ArcGIS, the image doesnt fit in my shapefile of districts. The districts looks smaller than the image of NDVI, but they should be overlaped. If you opened the file as SPOT DIMAP, do the bands have wavelengths shown in the Available Bands List? Wavelengths should be automatically assigned and you should see the wavelength next to the band name. For example, If they are not, you will need to define them in the header file. Go to FIle ->,Edit ENVI Header and select your SPOT file. Then go to Edit Attributes ->,Wavelengths. Add in the wavelength values for your SPOT data. FWHM values are not required if you do not have them. ENVI will estimate FWHM from the wavelengths and a gaussian distribution. Source.