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:
- Retrieve the parameters from the parameter block
- Open the LAS file for read access
- Open the geoTIFF file for writing
- Write the TIFF image fields from DDR information into the geoTIFF
- Write the geoTIFF image fields from DDR information into the geoTIFF
- if CREATE WORLD FILE then
- Write affine transformation to world file.
- end if
- Allocate buffers for LAS image and TIFF image
- Initialize processing message
- Read LAS image, one line at a time and write to geoTIFF in BIP forma
- Write out geoTIFF keys
- Close the geoTIFF and LAS file and free buffers
- Stop processing message
- Return successful completion message back to TAE
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