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I am working with idl in envi,I want to use ENVI_CONVERT_FILE_COORDINATES in case of finding pixel value of specified point,for this porpuse I have lat and long data of my point but I need to open image in IDL as a georefrenced image I noticed that image that is opened using ENVI_OPEN_FILE is not georefrenced,But if I open the same image using ENVI GUI it is georefrenced. So I think the problem is with opening image with its georefrenced data.

How do I open an georeferenced image in IDL?

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ENVI_OPEN_FILE can open a georeferenced image. You should use ENVI_GET_MAP_INFO function to get the map information. You can see this webpage

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  • Dear @JZH thank you for your help.So you mean after oppening file using ENVI_OPEN_FILE I call that function and It will fix the location of pixels base on lat and long? Nov 23, 2014 at 19:55
  • ENVI_GET_MAP_INFO can get the map info through the same fid opened by ENVI_OPEN_FILE. But if you want to get the lat and long of a pixel, use ENVI_CONVERT_FILE_COORDINATES.
    – JZH
    Nov 24, 2014 at 5:10
  • In fact I have a lat and long and I want to get their DN value on picture using IDL,SO I tried to use ENVI-CONVERT-FILE-CORDINATE but It gives me wrong data(I think it is because of not openning file as a georefrence image)..So what I shoould do?I must first open File using ENVI-OPEN_FILE Then using ENVI_GET_MAP_INFO get map info and then I use ENVI_CONVERT_FILE_COORDINATES to get DN values? Nov 24, 2014 at 12:31
  • 1, use ENVI_OPEN_FILE to open the georeferenced image (in this case, the map info is already prepared);2,use ENVI_CONVERT_FILE_COORDINATES with inputs of lat and lon to get the right pixel coordinate (make sure that the image is geographical projection to match the lat and lon)
    – JZH
    Nov 24, 2014 at 12:49
  • Thank you for your help.I used this code:ENVI> ENVI_OPEN_FILE,'E:\Subset_BIP.hdr', R_FID=FID, NO_REALIZE=1 ENVI> ENVI_OPEN_FILE,'E:\MASTER\Payan_Name\DataSer\Output\162\0730\1-1Georefrence_BIP\Subset_BIP.hdr', R_FID=FID, NO_REALIZE=1 ENVI> ENVI_CONVERT_FILE_COORDINATES,FID,xf,yf,Xloc,Yloc ENVI> Yloc=48.742834 ENVI> Xloc=31.345074 ENVI> ENVI_CONVERT_FILE_COORDINATES,FID,xf,yf,Xloc,Yloc ENVI> xf 54.553658073699950 ENVI> yf 3614.6857571678161 ENVI> but I think the result is not right,Does it must be a location of pixel?an integer number? Nov 24, 2014 at 16:38

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