[Liblas-devel] Re: Vertical Datum Transformation

Jason Woolard Jason.Woolard at noaa.gov
Fri Oct 29 13:22:16 EDT 2010


hi Ali,

There are a couple of ways to go about this. What I've done in the past is:

- Run las2txt on the LAS files
- Convert the ellipsoid heights to orthometric heights using VDatum. BTW- you can invoke a command line version of VDatum. The details and software are at: 
http://vdatum.noaa.gov/docs/userguide_cmd.html
-Run txt2las on the output from VDatum

It's a little convoluted but if you know a little Python or a similar language this can be done in pretty much one step.

Good luck! 


liblas-devel-request at lists.osgeo.org wrote:
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> Today's Topics:
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>    1. Re: las2txt question (Howard Butler)
>    2. Re: Re: las2txt question (Etienne Bellemare)
>    3. Vertical Datum Transformation (Ibraheem Ali)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Thu, 28 Oct 2010 15:22:29 -0500
> From: Howard Butler <hobu.inc at gmail.com>
> Subject: [Liblas-devel] Re: las2txt question
> To: Randy Bucciarelli <randy at cdip.ucsd.edu>
> Cc: "Liblas-devel at lists.osgeo.org" <liblas-devel at lists.osgeo.org>
> Message-ID: <3EBAF779-6E53-49C9-8705-CB1B9661D549 at gmail.com>
> Content-Type: text/plain; charset=us-ascii
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>
> On Oct 28, 2010, at 3:16 PM, Randy Bucciarelli wrote:
>
>   
>> Hi Howard,
>>
>> Is there a way to format resulting precision of values from the output of las2txt?
>>
>> Or does 'las2txt' simply output the precision of the values how there were initially stored when creating LAS files?
>>     
>
> There isn't, but I agree there should be an option to set/override the precision of x/y/z values (independently)  I have rewritten lasinfo and las2las using the new C++ API, and I think las2txt should also be rewritten as well.  In summary output and other venues in those rewritten utilities, I have tried to respect the specified scale/precision of the dimension if it was set in the header.  
>
> Rewriting las2txt similarly to lasinfo and las2las is in my queue, but I probably won't get to it for a bit.  
>
> Howard
>
> PS, this question should be asked on the list, and I have forwarded it there.
>
> ------------------------------
>
> Message: 2
> Date: Thu, 28 Oct 2010 16:44:53 -0400
> From: Etienne Bellemare <etiennebr at gmail.com>
> Subject: Re: [Liblas-devel] Re: las2txt question
> To: "Liblas-devel at lists.osgeo.org" <liblas-devel at lists.osgeo.org>
> Message-ID:
> 	<AANLkTikdhOeOVoKDew3V=TK1kP-tzJbVEwu-egf__9Cf at mail.gmail.com>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Good point, I'd like to suggest also the ability to specify the header
> separated the same way the fields are going to be. It will create a much
> more consistent file. e.g. for the moment you can't use tab to seperate
> header even if your fields are. Having the ability to set a name for the
> header could be a nice feature too.
>
> Thanks again,
> Etienne
>
> On Thu, Oct 28, 2010 at 4:22 PM, Howard Butler <hobu.inc at gmail.com> wrote:
>
>   
>> On Oct 28, 2010, at 3:16 PM, Randy Bucciarelli wrote:
>>
>>     
>>> Hi Howard,
>>>
>>> Is there a way to format resulting precision of values from the output of
>>>       
>> las2txt?
>>     
>>> Or does 'las2txt' simply output the precision of the values how there
>>>       
>> were initially stored when creating LAS files?
>>
>> There isn't, but I agree there should be an option to set/override the
>> precision of x/y/z values (independently)  I have rewritten lasinfo and
>> las2las using the new C++ API, and I think las2txt should also be rewritten
>> as well.  In summary output and other venues in those rewritten utilities, I
>> have tried to respect the specified scale/precision of the dimension if it
>> was set in the header.
>>
>> Rewriting las2txt similarly to lasinfo and las2las is in my queue, but I
>> probably won't get to it for a bit.
>>
>> Howard
>>
>> PS, this question should be asked on the list, and I have forwarded it
>> there._______________________________________________
>> Liblas-devel mailing list
>> Liblas-devel at lists.osgeo.org
>> http://lists.osgeo.org/mailman/listinfo/liblas-devel
>>
>>     
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> ------------------------------
>
> Message: 3
> Date: Fri, 29 Oct 2010 09:21:36 -0600
> From: Ibraheem Ali <ialhakeem at gmail.com>
> Subject: [Liblas-devel] Vertical Datum Transformation
> To: liblas-devel at lists.osgeo.org
> Message-ID:
> 	<AANLkTin-SzgrpAALbVLc9BXaQTn5afsF0o-D=zJ+1yo+ at mail.gmail.com>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Dear All,
>
> I'm a bit fresh with all LiDAR data processing and analysis.
>
> I've got recently a bunch of LiDAR "las" format files, and their Vertical
> datum is ellipsoidal "WGS 84". The vertical datum is not defined within the
> las files, it was givin to me as a fact from the vendor.
>
> I need to convert these files to NAVD88 Vertical Datum, and I basically need
> to perform the following steps:
>
>  1- Define the vertical datum (WGS 84) ellipsoidal within the files
> 2- Transform to NAVD 88
>
> I've got the "liblas" with "OSGeo w4", but I can not find a clear
> descriptions to the datums available or sample code regarding the above
> mentioned issue
>
> I would ask you kindly to help me with this, and would you please direct me
> to the right documentations?
>
> Thank you very much
>
> Ali
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