[Liblas-devel] Support for Variable Length Records

[Howard Butler]

All,

Building on some work by Mateusz, I have added support for VLRs to  
libLAS.  The most useful application of this support is the reading  
and writing of georeferencing information for LAS files, but it also  
allows us to carry forward VLRs as part of a LiDAR processing chain  
that includes programs like las2las.  The VLRs are carried around as  
part of the LASHeader, and you interact with them as if they are  
another header data member.

Frank Warmerdam helped us out with parsing and reading the  
georeferencing information, and there is now a LASHeader::GetProj4  
method that you can use to return the spatial reference of a LAS file  
that has VLRs describing the georeferencing information (actually,  
we've found very few of these files even though the spec says that all  
LAS files should have spatial referencing in the form of geotiff  
keys).  To utilize GetProj4, you must link a cvs head version of  
libgeotiff to libLAS with the --with-geotiff configure-time switch.

Because we also support linking with GDAL, I plan to implement a  
GetWKT() (or similarly named) method to the LASHeader that will  
support ESRI SRS WKT operations.

I think we should do a 0.9.7 release to provide the VLR and  
georeferencing work for people to test.  We need some good testing of  
this development with a wide variety of LAS files because the changes  
were a bit disruptive.

Howard