[pdal] Riegl extrabytes stripped

[Howard Butler]

> On Oct 3, 2016, at 7:59 AM, Kristian Evers <kreve at sdfe.dk> wrote:
> 
> Andrew,
> 
> I think, in the case of version 1.1-1.3 LAS files, that the format of the extrabytes are not specified in the VLR header. It is simply not possible in the format specification,

AFAIK, it is allowed to specify the extrabytes format for 1.0-1.3 LAS files. It's up to the software interpreting the specification to actually consume it, however. You are correct about extrabytes being allowed after the end of the fixed part of the point record, it's just that we had no way to communicate the interpretation of those bytes until the 1.4 version of the document.

> but it is still allowed to attach extra stuff at the end of a data record. How much extra stuff can be calculated from the information in the header about the record size, and the size of an un-altered record of a specific data format. I.e. knowing from the header that a record is 41 bytes and the data record point format 1 is 37 bytes we can infer that there must be 4 extra bytes in a record. What those bytes are is not specified in LAS files before version 1.4. And I guess that makes it hard for PDAL to understand how to treat those bytes, since there’s not a predefined dimension to put it in. Sorry if I am stating the obvious here, this stuff can be a bit confusing I think, so just trying make sure we agree on how to interpret the different LAS specifications.

I think one possibility is PDAL only uses this extrabytes machinery for 1.4 files and nothing earlier.