Hi Frank,
Thank you very much for the e-mail and the detailed info.
My data cover Texas coastal region (UTM zone 15), the lasinfo results
attached with this e-mail.
I've tried to run the code line you sent me, but the I always get " Program
stopped working" message.
I tried to assign the coordinate system with -a_srs but again same message.
Also, I tried the following, trying to figure out what is the problem:
1)
Caption from CMD:
C:\galveston_datum_conversion> las2las -i gal_000052.las --a_srs
error message:
error: required parameter is missing in 'a_srs'
2)
Caption from CMD:
C:\galveston_datum_conversion> las2las gal_000052.las --a_srs 32615
error message:
error: could not import coordinate system into OSRSpatialReference
SetFromUserInput
I would like to ask you if you may help me with this issue?
BTW: I'm a graduate student at UT_Dallas, and this is part of my research
project.
Thanks again for the information, your help is greatly appreciated.
Best regards,
Ibraheem Ali
On Fri, Oct 29, 2010 at 3:31 PM, Frank Warmerdam <[email protected]>wrote:
> Ibraheem Ali wrote:
>
>> 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?
>>
>
> Ali,
>
> Jason's approach with VDatum can certainly be used; however, over this
> year we have put some significant effort into adding vertical datum
> handling within liblas. With OSGeo4W this should be possible, but
> in addition to the liblas commandline tools package you will also need
> to ensure the "proj-vdatum" package is installed from under "Libraries"
> in the advanced install.
>
> If the file already has horizontal coordinate system information based
> on a geographic coordinate system using the WGS84 ellipsoid then the
> source data will already be considered as using WGS84 ellipsoidal heights.
>
> I have a source file (liblas/test/data/srs.las) which is marked as
> UTM 17 / WGS84. I can transform this to UTM 17 / WGS84 / NAVD88 with
> the command:
>
> las2las -i srs.las -o out.las --t_srs EPSG:32617+5703
>
> The coordinate system EPSG:32617+5703 is a shorthand way of telling
> las2las (or any OGRSpatialReference based application) to create a compound
> coordinate system consisting of EPSG:32617 as the horizontal coordinate
> system (UTM 11 / WGS84) and EPSG:5703 as the vertical coordinate system
> (NAVD88).
>
> The las2las command will (via PROJ.4) pick up the G2003conus.gtx file
> from C:\OSGeo4w\share\proj to convert from WGS84 ellipsoidal heights
> to NAVD88 based heights. The data file is also used by VDatum and
> in particular for WGS84/GRS80 <--> NAVD88 transformation I have compared
> the results between VDatum and this process with agreement to several
> decimal places. For the sample file the offsets are roughly 33m.
>
> Currently the only grid based vertical datum shift files provided with
> OSGeo4W are the 2003 geoid data for the USA (for NAVD88 / EPSG:5703),
> and the EGM 15 global data from 1996 (for EGM96 / EPSG:5773).
>
> Please let me know if you have any problems with this process.
>
> Best regards,
> --
>
> ---------------------------------------+--------------------------------------
> I set the clouds in motion - turn up | Frank Warmerdam,
> [email protected]
> light and sound - activate the windows | http://pobox.com/~warmerdam
> and watch the world go round - Rush | Geospatial Programmer for Rent
>
>
C:\galveston_datum_conversion>LASINFO gal_000050.las
---------------------------------------------------------
Header Summary
---------------------------------------------------------
Version: 1.2
Source ID: 0
Reserved: 0
Project ID/GUID: '00000000-0000-0000-0000-000000000000'
System ID: ''
Generating Software: 'TerraScan'
File Creation Day/Year: 0/0
Header Byte Size 227
Data Offset: 229
Number Var. Length Records: None
Point Data Format: 1
Number of Point Records: 802804
Number of Points by Return: 795410 7317 77 0 0
Scale Factor X Y Z: 0.01 0.01 0.01
Offset X Y Z: -0.00 -0.00 -0.00
Min X Y Z: 293000.00 3217225.40 -27.13
Max X Y Z: 293818.93 3217999.99 -3.60
Spatial Reference:
Geotiff_Information:
Version: 1
Key_Revision: 1.0
Tagged_Information:
End_Of_Tags.
Keyed_Information:
End_Of_Keys.
End_Of_Geotiff.
---------------------------------------------------------
Schema Summary
---------------------------------------------------------
Point Format ID: 1
Number of dimensions: 13
Custom schema?: false
Size in bytes: 28
Dimensions
---------------------------------------------------------
'X' -- size: 32 offset: 0
'Y' -- size: 32 offset: 4
'Z' -- size: 32 offset: 8
'Intensity' -- size: 16 offset: 12
'Return Number' -- size: 3 offset: 14
'Number of Returns' -- size: 3 offset: 14
'Scan Direction' -- size: 1 offset: 14
'Flightline Edge' -- size: 1 offset: 14
'Classification' -- size: 8 offset: 15
'Scan Angle Rank' -- size: 8 offset: 16
'User Data' -- size: 8 offset: 17
'Point Source ID' -- size: 16 offset: 18
'Time' -- size: 64 offset: 20
---------------------------------------------------------
Point Inspection Summary
---------------------------------------------------------
Header Point Count: 802804
Actual Point Count: 802804
Minimum and Maximum Attributes (min,max)
---------------------------------------------------------
Min X, Y, Z: 293000.00, 3217225.40, -27.13,
Max X, Y, Z: 293818.93, 3217999.99, -3.60,
Bounding Box: 293000.00, 3217225.40, 293818.93, 3217999.99
Time: 512076.970930, 516062.002566
Return Number: 1, 3
Return Count: 1, 3
Flightline Edge: 0, 1
Intensity: 3, 693
Scan Direction Flag: 0, 1
Scan Angle Rank: -24, 23
Classification: 1, 9
Point Source Id: 3, 7
User Data: 32, 32
Minimum Color: 0 0 0
Maximum Color: 0 0 0
Number of Points by Return
---------------------------------------------------------
(1) 795410 (2) 7317 (3) 77
Number of Returns by Pulse
---------------------------------------------------------
(1) 788090 (2) 14483 (3) 231
Point Classifications
---------------------------------------------------------
493613 Unclassified (1)
248639 Ground (2)
11971 High Vegetation (5)
48012 Building (6)
24 Low Point (noise) (7)
545 Water (9)
-------------------------------------------------------
0 withheld
0 keypoint
0 synthetic
-------------------------------------------------------
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