[Liblas-devel] Liblas-devel Digest, Vol 79, Issue 1

[Martin Isenburg]

Hi,

We created lasinfo so you can share an overview of the contents of LAS /
LAZ files without having to send the whole file ...

lasinfo -i sample.laz -odix _info -otxt

http://rapidlasso.com/lasinfo
http://lastools.org/download/lasinfo_README.txt
http://www.liblas.org/utilities/lasinfo.html

Regards,

Martin

On Wed, Nov 9, 2016 at 10:42 PM, Alexandre Guyot <alexguyot at yahoo.fr> wrote:

> Hi Martin,
>
> I've actually add a look at this *user_data* field but have a single
> value of '2' for all my points when reading with libLAS while the
> HEIGHT_ABOVE_GROUND attribute showing in GlobalMapper is ranging from
> -0.002 to 33.909.
>
> Cheers,
> Alex
>
>
>
>
>
> ------------------------------
> *De :* Martin Isenburg <martin.isenburg at gmail.com>
> *À :* Alexandre Guyot <alexguyot at yahoo.fr>
> *Cc :* Howard Butler <howard at hobu.co>; "Van Dyke, Daryl" <
> daryl_van_dyke at fws.gov>; "Liblas-devel at lists.osgeo.org" <
> liblas-devel at lists.osgeo.org>
> *Envoyé le :* Mercredi 9 novembre 2016 22h30
>
> *Objet :* Re: [Liblas-devel] Liblas-devel Digest, Vol 79, Issue 1
>
> Hi,
>
> in this case you are indeed just be storing HAG as a quantized value in
> decimeters (or decifeet) in the 8 bit unsigned user_data field that ranges
> from 0 to 255 (e.g. 0 to 25.5 meters or feet). See the README file of
> lasheight for details.
>
> http://lastools.org/download/ lasheight_README.txt
> <http://lastools.org/download/lasheight_README.txt>
>
> Furthermore you seem then to merely visualize the user_data field in
> Global Mapper and not a dedicated HAG field.
>
> Regards,
>
> Martin
>
> On Wed, Nov 9, 2016 at 9:55 PM, Alexandre Guyot <alexguyot at yahoo.fr>
> wrote:
>
> Hi,
>
> Thanks for your help.
> Actually, I havent' specified any switch in lasheight.
>
> My file is in LAS 1.2 and effectively has the HAG value as it can be read
> by some commercial software such as GlobalMapper (as "HEIGHT_ABOVE_GROUND"
> attribute).
>
> Is it therefore stored somewhere else than in extra-bytes or was LAS 1.2
> already using extra-bytes ?
>
> Thanks,
> Alex
>
>
>
>
> ------------------------------
> *De :* Howard Butler <howard at hobu.co>
> *À :* Martin Isenburg <martin.isenburg at gmail.com>
> *Cc :* "Van Dyke, Daryl" <daryl_van_dyke at fws.gov>; "
> Liblas-devel at lists.osgeo.org" <liblas-devel at lists.osgeo.org>
> *Envoyé le :* Mercredi 9 novembre 2016 21h29
> *Objet :* Re: [Liblas-devel] Liblas-devel Digest, Vol 79, Issue 1
>
>
> > On Nov 9, 2016, at 2:20 PM, Martin Isenburg <martin.isenburg at gmail.com>
> wrote:
> >
> > Hi,
> >
> > I believe that Alex talks about the HAG stored as an additional point
> atttribute to an "Extra Bytes" field via the '-store_as_extra_bytes' switch.
> >
> > http://lastools.org/download/ lasheight_README.txt
> <http://lastools.org/download/lasheight_README.txt>
> >
> > There was a discussion on this in the LAStools user forum whether cm
> resolution with a scale factor of 0.01 and a 16 bits signed integer storage
> are enough for most trees.
> >
> > http://groups.google.com/ forum/#!searchin/lastools/
> lasheight$20store_as_extra_ bytes
> <http://groups.google.com/forum/#!searchin/lastools/lasheight$20store_as_extra_bytes>
> >
> > "Extra Bytes" fields are described in the LAS 1.4 specification and are
> therefore also more and more readable in other software.
>
> All of this is accurate information.
>
> Additionally, libLAS does not support LAS 1.4 or support writing LAS 1.4
> extra bytes descriptor VLRs. You'll need to use LAStools or PDAL or LASpy
> to achieve this task if open source is a priority for you.
>
> Howard
>
> ______________________________ _________________
> Liblas-devel mailing list
> Liblas-devel at lists.osgeo.org
> http://lists.osgeo.org/ mailman/listinfo/liblas-devel
> <http://lists.osgeo.org/mailman/listinfo/liblas-devel>
>
>
>
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/liblas-devel/attachments/20161109/a7df8ccb/attachment.html>