Design Document for LAS2GEOTIFF

LAS2GEOTIFF

AUTHOR: Barry Olson

Functional Summary:

Convert a LAS image to a geoTIFF image.

Comments:

The current geoTIFF specification does not support the following projections:
  • Goode Homolosine
  • General Vertical Near-Side Perspective
  • Hammer
  • Interrupted Mollweide
  • Mollweide
  • Oblated Equal Area
  • Space Oblique Mercator
  • Wagner IV
  • Wagner VII
  • A geoTIFF image will still be created, but will not be complete. As much of the georeferencing information as possible is included with the geoTIFF image. Some information is not able to be brought over. Version 2 of the specification is suppose to handle most of these projections.

    Background:

    When exporting an image from LAS to TIFF format all the georeferencing information was lost. Extensions exist to the TIFF format that would allow most of the georeferencing information to be retained. Adding these extensions to the regular TIFF images would cause some TIFF viewers to be unable to display the images. It was decided to leave the LAS2TIFF functionality the same as it was and to create a new module to handle the geoTIFF extensions. This also allows the geoTIFF image to contain a number of bands other than 1 or 3.

    Requirements:

  • Images must contain required TIFF tags
  • Use geoTIFF extensions
  • Must handle LAS images regardless of number of bands
  • Support projections currently in LAS
  • Support sphereoids currently in LAS
  • Sub-windowing and sub-banding capabilities
  • Scope/Limitations:

  • Input image(s) must be LAS format
  • Overall design:

    Flow diagram:

    Postscript version available here


    Algorithm:

    Testing criteria:

  • Test single band image -- output should be grayscale image (PhotometricInterpretation = 1)
  • Test 3-band image -- output should be RGB full color image (PhotometricInterpretation = 2)
  • Test 2-band image -- output should be Separated band image (PhotometricInterpretation = 5)
  • Test 4-band (or more) image -- output should be Separated band image (PhotometricInterpretation = 5)
  • Test all error conditions
  • Test with LAS images of: maxlines, maxsamples, maxbands, and each pixel size (BYTE, I*2, I*4, FLOAT)
  • Test with LAS images of each spheroid and projection