[Liblas-devel] las 1.0 point data record format

[Howard Butler]

On Aug 12, 2010, at 9:45 AM, jasim wrote:

> Hi All,
> 
> I was trying to read the binary LAS files (version 1.0)... Have read everything from PUBLIC HEADER BLOCK and VARIABLE LENGTH RECORDS without any problems.
> 
> Currently having difficulty reading the POINT DATA... not in the sense that I cannot read but in the sense that I do not know which POINT DATA RECORD FORMAT to read for every point data...
> 
> According to "ASPRS LIDAR Data Exchange Format Standard" Version 1.0, May 9, 2003. There is POINT DATA RECORD FORMAT 0 and POINT DATA RECORD FORMAT 1.
> The only difference that I could spot is the last 8 byte double value in FORMAT 1 is additional, also the Scale Angle Rank Format in 0 is specified as char, but in Format 1 it is
> specified as unsigned char. In the above document before the Format 1 it says the following:
> "Other point data formats must be derived from the "Point Data 0" structure with the additional data added thereafter".
> 
> Probably I am missing something, if anyone could help me?
> My question is: so I read Point data in format 0, then how do I know whether the point data is in format 0 or 1? If anyone could
> clearly point to the result, I would be happy!

libLAS' points are returned to you regardless of the point format, and can be assumed to be equivalent to LAS 1.2's point format 3 (ie, all of format 0 + time + color).  Setting the point format in a header will cause points being written into that file to conform to the point format specified.  

Are you using libLAS, or is this a general LAS question?

Howard