How to access the classification information in a LAS Lidar file using the programming interface (API)

 ENVI Lidar can be used to read and view Lidar point clouds from LAS files.  It can sometimes be useful to get information from the file without importing it to ENVI Lidar.  The below code example shows how you can read the classification values held in a LAS file.

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PRO getLASclassifications

  COMPILE_OPT idl2

  CATCH,err
  IF err NE 0 THEN BEGIN
     CATCH, /CANCEL
     PRINT, 'Error: ' , !error_state.msg
     MESSAGE,/RESET

     IF OBJ_VALID(e) THEN BEGIN
       e.CLOSE
     ENDIF

     RETURN
  ENDIF

  e = e3de(/headless)
 
  ;provide the name of the classified pointcloud
  lasFileName = 'pointCloud_000.las'

  ;Directly read the input LAS file containing classification values
  oLidar = e3de.openlidar(lasFileName, /DIRECT_READ)
  
  startIndex = 0
  blockSize = 500000
  
  allread = 0

  WHILE (allread eq 0) DO BEGIN
    pointsInRange = oLidar.GetPointsInRange(startIndex, blockSize, $
                            ALL_ATTRIBS=ALL_ATTRIBS, $
                            COUNT=nPointsRead)
   
    ; *ALL_ATTRIBS.CLASSIFICATIONS returns the classification codes stored in
    ; the las file for this iteration of the WHILE LOOP
    inClass = *ALL_ATTRIBS.CLASSIFICATIONS
    IF (nPointsRead LT blocksize) THEN allread = 1

    startIndex += nPointsRead
  ENDWHILE
  
  e.CLOSE
END

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MM June 9, 2015