using las2las to project from UTM Zone 15 meters to Lambert Conformal Conic (of Ramsey County MN)

[Martin Isenburg]

Hello,

sometime questions are asked in the LinkedIn group of LAStools that you can find here:

http://www.linkedin.com/groups/LAStools-4408378

 

Thanks to Curt for asking this question (see at the end of the email) and for sharing his example data. Assuming that Curt meant "US survey feet" when saying "US foot" then the following command will do the re-projection (else change "survey_feet" to "feet").

las2las -i 4342-03-27_a_a.laz ^

           -target_lcc 500000 100000 survey_feet ^

                           44.79111111 -93.38333333 44.88333333 45.13333333 ^

           -target_elevation_feet ^

           -odix _llc -olaz

I actually created this command-line with the GUI of las2las.exe by specifying a target projection in the menu on the right (see attached image). Afterwards I had to slightly correct the first eight decimal digits of the degree values in the RUN window that pops up ....

Running this lasgrid command afterwards produces a nice PNG raster together with a corresponding KML file that shows up at the exact right location in Google Earth:

lasgrid -i 4342-03-27_a_a_llc.laz ^

          -elevation -highest ^

          -false -set_min_max 900 1000 ^

          -opng

There is a nice tutorial on some simple LAStools operations by Tim Loesch from the DNR Minnesota that you may find useful:

ftp://lidar.dnr.state.mn.us/documentation/LAS_File_Processing_Using_LASTOOLS.pdf

Cheers,

Martin

---

I'm having difficulty projecting LAZ to LAS using Las2Las.exe to prepare files to be read by AutoCAD C3D for design engineering.

I have a bunch of MN DNR LiDAR LAZ data that I would like to project from UTM Zone 15 meters to Ramsey Coounty MN Coordinates using the Las2Las.exe tool. The projection parameters for the Ramsey County Coordiante System are as follows: ... more… 
I have a bunch of MN DNR LiDAR LAZ data that I would like to project from UTM Zone 15 meters to Ramsey Coounty MN Coordinates using the Las2Las.exe tool. The projection parameters for the Ramsey County Coordiante System are as follows: 

Projection: Lambert Conformal Conic 
False Easting: 500000.00 
False Northing: 100000.00 
Central Meridian: -93.3833333334 
Latitude of Origin: 44.7911111111 
First Standard Parallel: 44.8833333333 
Second Standard Parallel: 45.1333333333 
Horizontal Unit: US Foot 
Vertical Unit: Feet 

A sample LAZ file has been uploaded to our public FTP site at:ftp://ftp.co.ramsey.mn.us/PubWorks/Outgoing/LAZLAS/ filename: 4342-03-27_a_a.laz 

Thanks for your assistance! 
Curt Peterson

[Loesch, Tim N (MNIT)]

Martin,

 

I was not able to get the projection to work properly following the process you suggested. I still get an offset that was giving me trouble in the past. The image below shows what I see….

 

Now the image is in UTM Zone 15 NAD83 and from what I can tell the Ramsey county coordinates are the same as the Hennepin county coordinates. What I don’t know is if the offset is due to a display transformation issue or if it is really off but I suspect it is the data…..

 

 

 

Any other suggestions?

 

tim

 

 

Timothy N. Loesch | GIS Operations Supervisor

MN.IT Services @ Department of Natural Resources
Phone:  (651) 259-5475 (w) | tim.l...@state.mn.us | Lat 44.95609, Long -93.08388

Information Technology for Minnesota Government

|   mn.gov/oet

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[Martin Isenburg]

Hello Tim and Curtis,

The issue was that las2las.exe was always converting the horizontal units to metric (meters) when re-projecting to a lambert conformal conic projection. While this should have placed the points to the correct position (just with a different unit) the latest release (130817) of LAStools gives re-projected lambert conformal conic coordinates the requested unit. So on the example data that Curtis provided I ran the following to do the conversion for the first 100,000 points (attached to this message) and followed this with a las2dem hillshade (attached) that aligns correctly in Google Earth and the lasinfo output. Can someone check if this LAZ file loads correctly into ArcGIS (you will need to uncompress to LAS first).

las2las -i 4342-03-27_a_a.laz ^

           -target_lcc 500000 100000 survey_feet ^

                           44.79111111 -93.38333333 ^

                           44.88333333 45.13333333 ^

           -target_elevation_feet ^
           -odix _llc -olaz ^
           -subseq 0 100000

las2dem -i 4342-03-27_a_a_llc.laz -hillshade -opng

lasinfo -i 4342-03-27_a_a_llc.laz

reporting all LAS header entries:

  file signature:             'LASF'

  file source ID:             0

  global_encoding:            0

  project ID GUID data 1-4:   00000000-0000-0000-0000-000000000000

  version major.minor:        1.2

  system identifier:          'LAStools (c) by Martin Isenburg'

  generating software:        'las2las (version 130817)'

  file creation day/year:     235/2012

  header size:                227

  offset to point data:       677

  number var. length records: 3

  point data format:          1

  point data record length:   28

  number of point records:    100000

  number of points by return: 84849 14445 693 13 0

  scale factor x y z:         0.01 0.01 0.001

  offset x y z:               500000 100000 0

  min x y z:                  551678.95 153068.33 911.713

  max x y z:                  552259.59 153360.16 1006.070

variable length header record 1 of 3:

  reserved             43707

  user ID              'LASF_Projection'

  record ID            34735

  length after header  112

  description          'by LAStools of Martin Isenburg'

    GeoKeyDirectoryTag version 1.1.0 number of keys 13

      key 1024 tiff_tag_location 0 count 1 value_offset 1 - GTModelTypeGeoKey: ModelTypeProjected

      key 3072 tiff_tag_location 0 count 1 value_offset 32767 - ProjectedCSTypeGeoKey: user-defined

      key 3075 tiff_tag_location 0 count 1 value_offset 8 - ProjCoordTransGeoKey: CT_LambertConfConic_2SP

      key 3076 tiff_tag_location 0 count 1 value_offset 9003 - ProjLinearUnitsGeoKey: Linear_Foot_US_Survey

      key 3078 tiff_tag_location 34736 count 1 value_offset 0 - ProjStdParallel1GeoKey: 44.88333333

      key 3079 tiff_tag_location 34736 count 1 value_offset 1 - ProjStdParallel2GeoKey: 45.13333333

      key 3088 tiff_tag_location 34736 count 1 value_offset 2 - ProjCenterLongGeoKey: -93.38333333

      key 3081 tiff_tag_location 34736 count 1 value_offset 3 - ProjNatOriginLatGeoKey: 44.79111111

      key 3082 tiff_tag_location 34736 count 1 value_offset 4 - ProjFalseEastingGeoKey: 500000

      key 3083 tiff_tag_location 34736 count 1 value_offset 5 - ProjFalseNorthingGeoKey: 100000

      key 2056 tiff_tag_location 0 count 1 value_offset 7019 - GeogEllipsoidGeoKey: Ellipse_GRS_1980

      key 4099 tiff_tag_location 0 count 1 value_offset 9002 - VerticalUnitsGeoKey: Linear_Foot

      key 4096 tiff_tag_location 0 count 1 value_offset 5103 - VerticalCSTypeGeoKey: VertCS_North_American_Vertical_Datum_1988

variable length header record 2 of 3:

  reserved             43707

  user ID              'LASF_Projection'

  record ID            34736

  length after header  48

  description          'by LAStools of Martin Isenburg'

    GeoDoubleParamsTag (number of doubles 6)

      44.8833 45.1333 -93.3833 44.7911 500000 100000

variable length header record 3 of 3:

  reserved             0

  user ID              'FugroHorizons'

  record ID            0

  length after header  128

  description          'FHZNInfo'

LASzip compression (version 2.2r0 c2 50000): POINT10 2 GPSTIME11 2

reporting minimum and maximum for all LAS point record entries ...

  X    5167895    5225959

  Y    5306833    5336016

  Z     911713    1006070

  intensity 39 400

  edge_of_flight_line 0 1

  scan_direction_flag 1 1

  number_of_returns_of_given_pulse 1 4

  return_number                    1 4

  classification      1     8

  scan_angle_rank   -30    25

  user_data           0     3

  point_source_ID  1301  1303

  gps_time 459139.898465 461070.703339

overview over number of returns of given pulse: 87899 11802 295 4 0 0 0

histogram of classification of points:

           13623  Unclassified (1)

           42498  Ground (2)

            4313  Low Vegetation (3)

            2994  Medium Vegetation (4)

           13435  High Vegetation (5)

           20065  Building (6)

            3072  Model Key-point (mass point) (8)

[Tommy Jordan]

I imported the decompressed LAS file into an ArcGIS LASD dataset and then brought up the World Image basemap behind the points.  The projection info in the header is correct in ArcCatalog - the horizontal projection is exactly correct and the units are right.  The vertical datum information shows up as 'unknown' but the vertical units are feet.

It seems to be a bit off in position when overlaid on the world image basemap.  Don't know if it is the reprojection or the image data that is off in this case.  Screen shot attached.  the lidar shift looks to be about 25 m south and 25 m east, as best I can tell from looking at the features.  Someone who knows the data and area may be able to figure it out better.

Tommy

fun little exercise with my coffee this morning.

On Sun, Aug 18, 2013 at 6:43 AM, Martin Isenburg <martin....@gmail.com> wrote:

Hello Tim and Curtis,

The issue was that las2las.exe was always converting the horizontal units to metric (meters) when re-projecting to a lambert conformal conic projection. While this should have placed the points to the correct position (just with a different unit) the latest release (130817) of LAStools gives re-projected lambert conformal conic coordinates the requested unit. So on the example data that Curtis provided I ran the following to do the conversion for the first 100,000 points (attached to this message) and followed this with a las2dem hillshade (attached) that aligns correctly in Google Earth and the lasinfo output. Can someone check if this LAZ file loads correctly into ArcGIS (you will need to uncompress to LAS first).

las2las -i 4342-03-27_a_a.laz ^

           -target_lcc 500000 100000 survey_feet ^

                           44.79111111 -93.38333333 ^

                           44.88333333 45.13333333 ^

           -target_elevation_feet ^

--

Thomas R. Jordan, Ph.D., CP, CMS
Associate Director
Center for Geospatial Research
Department of Geography   University of Georgia
Athens, GA  30602
706-542-2372
tom...@uga.edu
http://www.crms.uga.edu