convert LAS file from WGS84 UTM zone 11 to NAD83 UTM zone 11N

[Alessandro Montaghi]

Hi all,

I have several las files format in WGS84 UTM zone 11 and i wish to convert in NAD83 UTM zone 11N using las2las batch file. I tried several combination but with result. Anyone know the right code command?

thanks in advance

Ale  

[Kirk Waters - NOAA Federal]

There may be a way to do it in las2las, but I'd suggest trying the VDatum tool at vdatum.noaa.gov. It should handle LAS files, though not LAZ. Its focus is vertical datum transformations. You won't need all the tidal grids for what you're doing, so you should be able to do a smaller download.

Kirk Waters, PhD                     | NOAA Office for Coastal Management

Applied Sciences Program      | 2234 South Hobson Ave
843-740-1227                          | Charleston, SC 29405    

coast.noaa.gov/digitalcoast

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[Terje Mathisen]

Alessandro Montaghi wrote:
> Hi all,
>
> I have several las files format in WGS84 UTM zone 11 and i wish to
> convert in NAD83 UTM zone 11N using las2las batch file. I tried
> several combination but with result. Anyone know the right code command?
>
>

Kirk W have already replied with the proper, maximally accurate method,
but I have to ask:

Why do you need to convert them? Afaik WGS84 and NAD83 differ only at
the continental plate drift rate, which isn't really that significant
over the last 30 years?

I.e. what's the required final precision?

Terje

--
- <Terje.M...@tmsw.no>
"almost all programming can be viewed as an exercise in caching"

[Alessandro Montaghi]

Thanks Terje, 

The commissioner of this data processing expressively requests the final data in NAD83 11N (PS: normally i used always and only wgs84). all yesterday, i tried several setting in las2las but without results.  

[Kirk Waters - NOAA Federal]

Terje is correct that the horizontal difference between wgs84 and nad83 is not great (though also not zero). However, you have to be careful about what is being done in the transform and what your vertical datum is. NAD83 and WGS84 are both 3D datums and the shift between them is generally using equations that affect all three dimensions. If you take WGS84 ellipsoid heights and transform to NAD83 ellipsoid heights, the z-values may shift on the order of a meter (depending where in the world you are). 

As an example, I used the interactive Horizontal Time-Dependent Positioning tool from NOAA/NGS (https://www.ngs.noaa.gov/TOOLS/Htdp/Htdp.shtml) to transform a point in the U.S. Southeast. I set the begin and end times to 2015.0, so there is no temporal shift. You can see in the figure below that the ellipsoid height has changed by -1.5 meters.

Kirk Waters, PhD                     | NOAA Office for Coastal Management

Applied Sciences Program      | 2234 South Hobson Ave
843-740-1227                          | Charleston, SC 29405    

coast.noaa.gov/digitalcoast

[Terje Mathisen]

Alessandro Montaghi wrote:
> Thanks Terje,
>
> The commissioner of this data processing expressively requests the
> final data in NAD83 11N (PS: normally i used always and only wgs84).
> all yesterday, i tried several setting in las2las but without results.

Can you get away with a static adjustment. I.e. if the processed area is
of somewhat limited size, then you could lookup the (x,y,z) offset
between WGS84 and NAD83 for one or more of the closest CORS stations,
then use that the adjust every point by the same amount?

Looking at
https://confluence.qps.nl/pages/viewpage.action?pageId=29855153 I see
that the latest version of NAD83 for USA CONUS is 2010.00 which was
defined in 2011. Is this the one you want?

The linked spreadsheet gives delta values in the 1-2 m range between
NAD83(2011) and ITRF which coincides with WGS84 at the 10 cm level.

Terje

>
> 2015-02-11 0:42 GMT-07:00 Terje Mathisen <terje.m...@tmsw.no

> <mailto:terje.m...@tmsw.no>>:

>
> Alessandro Montaghi wrote:
>
> Hi all,
>
> I have several las files format in WGS84 UTM zone 11 and i
> wish to convert in NAD83 UTM zone 11N using las2las batch
> file. I tried several combination but with result. Anyone know
> the right code command?
>
>
> Kirk W have already replied with the proper, maximally accurate
> method, but I have to ask:
>
> Why do you need to convert them? Afaik WGS84 and NAD83 differ only
> at the continental plate drift rate, which isn't really that
> significant over the last 30 years?
>
> I.e. what's the required final precision?
>
> Terje
>
> --

> - <Terje.M...@tmsw.no <mailto:Terje.M...@tmsw.no>>

[Alessandro Montaghi]

Dear Terje, 

I am working in North of Canada where the closest CORS stations (road, towns and pubs) are very very very very very far from my study area.

Thanks Kirk, 

I will try to use your software because i didn't find a solution to my problem with las2las. I am working on WGS84 - 11n and i need to convert in NAD83 11n (because it's the standard system here). 

[Evon Silvia]

Alessandro,

Since you're in Canada, you might give the TRX tool a try to come up with the transformation in your area. I believe it's more or less the Canadian equivalent of HTDP, for transforming between epochs and between realizations of NAD83 and ITRF. Each iteration of ITRF is approximately equivalent to the corresponding realization of WGS84.

Here's a link: http://webapp.geod.nrcan.gc.ca/geod/tools-outils/trx.php?locale=en

Evon

[Nicolas Cadieux]

Hi,
Good tools here also.  Some may only apply to Canada. Most will permit processing of huge .txt files. So las2txt could be useful. I have used this for large lidar file.

http://www.nrcan.gc.ca/earth-sciences/geomatics/geodetic-reference-systems/tools-applications/10925

Kirk, are you aware of a more precise way to calculate wgs84/emg96 geoid than the tools given here?

http://earth-info.nga.mil/GandG/wgs84/gravitymod/egm96/egm96.html

Nicolas Cadieux M.Sc.
Les Entreprises Archéotec inc. 
8548, rue Saint-Denis Montréal H2P 2H2
Téléphone: 514.381.5112  Fax: 514.381.4995

Le 2015-02-10 18:00, Kirk Waters - NOAA Federal <kirk....@noaa.gov> a écrit :

There may be a way to do it in las2las, but I'd suggest trying the VDatum tool at vdatum.noaa.gov. It should handle LAS files, though not LAZ. Its focus is vertical datum transformations. You won't need all the tidal grids for what you're doing, so you should be able to do a smaller download.

Kirk Waters, PhD                     | NOAA Office for Coastal Management

Applied Sciences Program      | 2234 South Hobson Ave
843-740-1227                          | Charleston, SC 29405    

coast.noaa.gov/digitalcoast

On Tue, Feb 10, 2015 at 4:05 PM, Alessandro Montaghi <alessandr...@gmail.com> wrote:

Hi all,

I have several las files format in WGS84 UTM zone 11 and i wish to convert in NAD83 UTM zone 11N using las2las batch file. I tried several combination but with result. Anyone know the right code command?

thanks in advance

Ale  

--
Download LAStools at
http://lastools.org
http://rapidlasso.com
Be social with LAStools at
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[Kirk Waters - NOAA Federal]

Nicholas,

I'd suggest using the EGM2008 instead of EGM96. The grids and some software are at http://earth-info.nga.mil/GandG/wgs84/gravitymod/egm2008/egm08_wgs84.html. But... I think it's going to leave you unsatisfied unless you're willing to do some programming. The software isn't going to pull in your las/laz files. I coded the grids into software that can work with las (which is why Digital Coast has EGM08 as an output option), but it might be easier to turn the grids into something that lasheight can use. For example, see https://groups.google.com/forum/#!msg/lastools/w5BSoviHt8c/7_YAg5yDM0wJ

That might still take some coding and understanding the grid structure to make the txt file of just the area you need, but it's an easier task.

Kirk

--

Kirk Waters, PhD                     | NOAA Office for Coastal Management

Applied Sciences Program      | 2234 South Hobson Ave
843-740-1227                          | Charleston, SC 29405    

coast.noaa.gov/digitalcoast

[Nicolas Cadieux]

Hi,
Thanks for the info.  I am working with EMG96 because that is what the SRTMs and GDEMs are in. I am using the CGVD2013 instead (Canada official datum).  I was wondering if there was more precise tools to work with EMG96 then those found in the link. I believe it's a 15 min grid for EMG96.

http://earth-info.nga.mil/GandG/wgs84/gravitymod/egm96/egm96.html

Nicolas Cadieux M.Sc.
Les Entreprises Archéotec inc. 
8548, rue Saint-Denis Montréal H2P 2H2
Téléphone: 514.381.5112  Fax: 514.381.4995