[Liblas-devel] PROJ4 / Georeference info?

[Mateusz Loskot]

Howard Butler pisze:
> 
> On Oct 29, 2008, at 10:27 PM, Jason Woolard wrote:
> 
>>
>> Thanks for the great work here. The library is working quite well. I 
>> have another quick question though. Sorry if I'm missing something 
>> obvious.
>>
>> I'm trying to add projection and georeference info to LAS header files 
>> that currently don't have any projection info. I was thinking 
>> something like this would work:
>>
>> >>> from liblas import file
>> >>> infile = liblas.file.File('C:\\liblas_test\\debug.las',mode='r')
>> >>> h = infile.header
>> >>> h.proj4 ='+proj=utm +zone=17 +ellps=WGS84 +units=m'
>> >>> h.proj4
>> '+proj=utm +zone=17 +ellps=WGS84 +units=m'
>> >>> outfile = 
>> liblas.file.File('C:\\liblas_test\\debug_junk.las',mode='w', header=h)
>> >>> outfile.header.proj4
>> '+proj=utm +zone=17 +ellps=WGS84 +units=m'
>> >>> outfile.close()
>> >>> outfile = 
>> liblas.file.File('C:\\liblas_test\\debug_junk.las',mode='r')
>> >>> outfile.header.proj4
>> ''
>> >>>
> 
> 
> 
> You have to write a point to the file or it is not valid.  I guess we 
> should update the wiki to reflect this...  I also wonder if maybe we 
> should have the writer try to throw an exception when nPoints is 0...

Hobu,

I'm not convinced to throw on Zero records.
I believe that documenting it should be enough.
Perhaps we could add new functionality for LAS file validation.
This could go be added to LASReader/LASWriter or - my favorite - as a 
new class, ie. LASValidator, where complex validation logic could be 
implemented (Zero number of points included).


Best regards,
-- 
Mateusz Loskot, http://mateusz.loskot.net
Charter Member of OSGeo, http://osgeo.org