[Liblas-devel] LAS file Coordinate Systems

[Patel, Ronak Avinash (US SSA)]

Howard,

So I see the Geotiff spec describe the GeoKeyDirectoryTag Record tag at:

http://remotesensing.org/geotiff/spec/geotiff2.4.html as

GeoKeyDirectoryTag=(   1,     1, 2,     6,
                      1024,     0, 1,     2,
                      1026, 34737,12,     0,
                      2048,     0, 1, 32767,
                      2049, 34737,14,    12,
                      2050,     0, 1,     6,
                      2051, 34736, 1,     0 )
  GeoDoubleParamsTag(34736)=(1.5)
  GeoAsciiParamsTag(34737)=("Custom File|My Geographic|")

I am writing:

		    (1, 1, 0, 4)
		    (1025, 0, 1, 2)
		    (1024, 0, 1, 2)
		    (2048, 0, 1, 4326)
		    (4097, 0, 1, 9001)

In code this translates to:

final ByteBuffer wrap = ByteBuffer.allocate(40);
		
wrap.putShort((short) 1);
wrap.putShort((short) 1);
wrap.putShort((short) 0);
wrap.putShort((short) 4);
		
wrap.putShort((short) GeoTiffConstants.GTRasterTypeGeoKey);
wrap.putShort((short) 0);
wrap.putShort((short) 1);
wrap.putShort((short) GeoTiffConstants.RasterPixelIsPoint);
		
wrap.putShort((short) GeoTiffConstants.GTModelTypeGeoKey);
wrap.putShort((short) 0);
wrap.putShort((short) 1);
wrap.putShort((short) GeoTiffGCSCodes.ModelTypeGeographic);
		
wrap.putShort((short) GeoTiffGCSCodes.GeographicTypeGeoKey);
wrap.putShort((short) 0);
wrap.putShort((short) 1);
wrap.putShort((short) GeoTiffGCSCodes.GCS_WGS_84);
		
wrap.putShort((short) GeoTiffVCSCodes.VerticalCitationGeoKey);
wrap.putShort((short) 0);
wrap.putShort((short) 1);
wrap.putShort((short) GeoTiffUoMCodes.Linear_Meter);

Does this make sense? It does according to page 14 of the LAS 1.2
spec....
If so, why does lasinfo.exe say that it can't read this tag?

-----Original Message-----
From: Howard Butler [mailto:hobu.inc at gmail.com] 
Sent: Thursday, July 23, 2009 1:30 PM
To: Patel, Ronak Avinash (US SSA)
Cc: Liblas-devel at lists.osgeo.org
Subject: Re: [Liblas-devel] LAS file Coordinate Systems

Are you by chance confusing LAStools with libLAS?

LAStools has a partial implementation of some geotiff key reading/ 
writing.  libLAS, which implements the command line utilities of  
LAStools, uses libgeotiff for geotiff key reading/writing and provides  
a much more complete implementation.

Your results will differ depending on which one (LAStools or libLAS)  
you are using.

Howard


On Jul 23, 2009, at 3:00 PM, Patel, Ronak Avinash (US SSA) wrote:

> I am using lasinfo.exe to display the fields. I downloaded lastools
> separately for Windows.
>
>
> -----Original Message-----
> From: liblas-devel-bounces at lists.osgeo.org
> [mailto:liblas-devel-bounces at lists.osgeo.org] On Behalf Of Howard  
> Butler
> Sent: Thursday, July 23, 2009 12:55 PM
> To: Liblas-devel at lists.osgeo.org
> Subject: Re: [Liblas-devel] LAS file Coordinate Systems
>
>
> On Jul 23, 2009, at 1:39 PM, Patel, Ronak Avinash (US SSA) wrote:
>
>> Howard and Mateusz,
>>
>> Thanks for the help...really appreciate it. Haven't really found many
>> people out there that know the low levels as much as you guys do.
>>
>> I was looking at the LAS 1.2 spec and it says the Georeferencing
>> information requires the GeoKeyDirectoryTag Record.
>>
>> I am able to write that tag out but I see that lasinfo always shows
>> the
>> version to be 0.0.0 regardless of what I put in those fields.
>>
>> According to the spec, the data should be arranged:
>>
>> wKeyDirectoryVersion = 1 (2 bytes)
>> wKeyRevision = 1 (2 bytes)
>> wMinorRevision = 0 (2 bytes)
>> wNumberOfKeys  = the number of sets of 4 unsigned shorts to follow
>>
>> I write out the above shorts and 0 out the rest of the data byte  
>> array
>> but lasinfo always shows 0.0.0 as the version.
>>
>> Is the spec wrong? Or is something else going on here that lasinfo  
>> and
>> libLAS are doing??
>
> Are you linking libLAS with libgeotiff when you compile?  libLAS
> completely ignores georeferencing if libgeotiff is not linked at
> compile time.
>
> Howard
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