[pdal] Setting SRS on las file

[Matthew Hanson]

Thanks to you both, this is indeed helpful

Matthew Hanson
Applied GeoSolutions
(603) 659-3363 x91
http://appliedgeosolutions.com
mhanson at appliedgeosolutions.com


On Sun, Feb 8, 2015 at 10:55 AM, Howard Butler <howard at hobu.co> wrote:

>
> > On Feb 6, 2015, at 2:13 PM, Matthew Hanson <
> mhanson at appliedgeosolutions.com> wrote:
> >
> >
> > We have las files that have no spatial reference embedded in the file.
>  For one, I'm not sure it's necessary to actually add the spatial reference
> to the las file.  We want to create DEM's, so perhaps it's better to just
> leave them as is then set the SRS on the final GeoTiffs.
> >
> > However, for the moment assuming that this makes sense, when I run pdal
> translate
> > $ pdal translate -i input.las -o output.las -a_srs EPSG:XXXXX
> >
> > I get a file that is bigger than the original because it's seemed to add
> 4 new dimensions: Time, Red, Green, Blue.   The original file did not have
> them, although I notice that lasinfo reports min and max for all those
> fields in both files, even though they are missing from the original.
> >
> > Are these standard dimensions in las files, and is there any way to
> control if they are added or not?
>
> Control it with the "format" option, and set it to 0 if you don't want
> Time or RGB. It defaults to 3, which includes those dimensions.
>
> > $ pdal translate -i input.las -o output.las -a_srs EPSG:XXXXX
> --writers.las.format=0
>
>
> >  If we want to add the SRS to files, I'd rather not increase the size of
> them all.  Although maybe this is moot since, as per above, it just doesn't
> make sense to add the SRS anyway.
>
> It is probably easiest to leave the SRS alone until the final GeoTIFF
> write (and then set it with a GDAL VRT). The only advantage of setting it
> on the file before processing is so you don't have to do it in a later step.
>
> Another problem here is setting the SRS is going to cause a rewrite of the
> entire file due to the VLRs needing to be modified. This is one entire
> extra i/o step that's not needed.
>
> Hope this helps,
>
> Howard
>
>
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