Hi, I am having trouble to retrive a pixel value by geographic long lats. Following is the code. two values obtained by sample/line coordinate and geographic long lats are different. What is wrong with my code? Thanks ;====================================================== ;Open a file using envi batch envi_open_file, fNameInput, r_fid=fid if (fid eq -1) then begin envi_batch_exit return endif ; ; Open the file to read in array OpenR, Lun, fNameInput,/Get_Lun ; Setup the values for the keywords envi_file_query, fid, ns=ns, nl=nl, nb=nb, data_type=data_type,$ interleave=interleave, dims=dims Image=Make_Array(ns,nl,nb); create an array to get the values of the image readu, lun, Image; read the image pixel values into the array Free_Lun, Lun ;print a pixel value by sample and rows print, image[1040, 404, *] ;this prints pixel values for 6 bands ; this fine, correct ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;Retrieve a pixel value by geographic long lats ;get coordinates for image and convert to lat/lon xcoord=116.521 ycoord= 40.1455 ;change from lat/long coordinates to pixel values ENVI_CONVERT_File_COORDINATES, fid, xF, yF,xcoord, ycoord for nb=0, nb-1 do begin ;read multi band data data = ENVI_GET_DATA(fid=fid, dims=dims, pos=nb); pos is the name of the band, 0=1st band, 5=6th band output=data[xcoord, ycoord,*] print, output; this prints pixel values for 6 bands endfor ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;