lasinfo spatial reference difference between LAStools and libLAS
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Greg Flanagan
Dec 30, 2015, 3:33:25 PM12/30/15
to LAStools - efficient tools for LiDAR processing
I'm transitioning from libLAS to LAStools and I've having an issue with the spatial reference reported by LAStools.
Using libLAS I get the following WKT:
> lasinfo file.las
PROJCS["NAD83 / California zone 3 (ftUS)",
GEOGCS["NAD83",
DATUM["North_American_Datum_1983",
SPHEROID["GRS 1980",6378137,298.2572221010002,
AUTHORITY["EPSG","7019"]],
AUTHORITY["EPSG","6269"]],
PRIMEM["Greenwich",0],
UNIT["degree",0.0174532925199433],
AUTHORITY["EPSG","4269"]],
PROJECTION["Lambert_Conformal_Conic_2SP"],
PARAMETER["standard_parallel_1",38.43333333333333],
PARAMETER["standard_parallel_2",37.06666666666667],
PARAMETER["latitude_of_origin",36.5],
PARAMETER["central_meridian",-120.5],
PARAMETER["false_easting",6561666.667],
PARAMETER["false_northing",1640416.667],
UNIT["US survey foot",0.3048006096012192,
AUTHORITY["EPSG","9003"]],
AUTHORITY["EPSG","2227"]]
Using LAStools I get
> lasinfo file.las
LOCAL_CS["GCS_North_American_1983",
GEOGCS["NAD83",
DATUM["North_American_Datum_1983",
SPHEROID["GRS 1980",6378137,298.2572221010002,
AUTHORITY["EPSG","7019"]],
AUTHORITY["EPSG","6269"]],
PRIMEM["Greenwich",0],
UNIT["degree",0.0174532925199433],
AUTHORITY["EPSG","4269"]],
AUTHORITY["EPSG","2227"],
UNIT["US survey foot",0.3048006096012192]]
Any ideas what could be happening here? I using the same version of gdal, libgeotiff and proj4.
Greg
Martin Isenburg
Dec 30, 2015, 3:42:28 PM12/30/15
to LAStools - efficient command line tools for LIDAR processing
Hi Greg.
you need to share a few more details here. Who generated the LAS file? You? Ideally post a *link* to a small sample LAS (or better LAZ) file. Without knowing anything more I would assume that the lasinfo of libLAS elaborates on the full meaning of the EPSG code 2227 (see [1]) and gives all the details about the Lambert_Conformal_Conic_2SP projection is refers to whereas lasinfo of LAStools only reports the information actually stored in the LAS file without interpreting it further ... ?
Regards,
Martin @rapidlasso
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Kirk Waters - NOAA Federal
Dec 30, 2015, 3:58:20 PM12/30/15
to LAStools - efficient command line tools for LIDAR processing
Martin and Greg,
I usually see the LOCAL_CS from LAStools when the EPSG code hasn't been coded in yet. A grep for 2227 on the LAStools geoprojectionconverter.cpp file from a couple days ago suggests that's the case. While gdal and libLAS use proj.4, LAStools does not, and that where libLAS is finding EPSG:2227. Unfortunately, the EPSG codes for the state plane system that you'll find in the GeoTIFF documentation are all defined with horizontal units of meters. The EPSG:2227 is the right one for getting feet in California zone 3 instead of EPSG:26943, which is in LAStools but uses meters.
Kirk
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Applied Sciences Program | 2234 South Hobson Ave
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843-740-1227 | Charleston, SC 29405
Martin Isenburg
Jan 7, 2016, 4:03:20 AM1/7/16
to LAStools - efficient command line tools for LIDAR processing
Hello Greg and Kirk,
with the latest LAStools release (160106) the above issue should have been resolved. Below a little test with the EPSG code 2227. Note that fusa.laz is in Autralia so this makes no real sense but shows that the EPSG code is now recognized. Also ... for the correct vertical units you would need to add '-elevation_survey_feet' or '-elevation_feet' to the command line.
Regards,
Martin @rapidlasso
D:\LAStools\bin>las2las -i ..\data\fusa.laz -o mist.laz -epsg 2227
D:\LAStools\bin>lasinfo -i mist.laz
lasinfo report for mist.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: 1.1
system identifier: 'LAStools (c) by rapidlasso GmbH'
generating software: 'las2las (version 160106)'
file creation day/year: 40/2010
header size: 227
offset to point data: 321
number var. length records: 1
point data format: 1
point data record length: 28
number of point records: 277573
number of points by return: 263413 13879 281 0 0
scale factor x y z: 0.01 0.01 0.01
offset x y z: 0 0 0
min x y z: 277750.00 6122250.00 42.21
max x y z: 277999.99 6122499.99 64.35
variable length header record 1 of 1:
reserved 43707
user ID 'LASF_Projection'
record ID 34735
length after header 40
description 'by LAStools of rapidlasso GmbH'
GeoKeyDirectoryTag version 1.1.0 number of keys 4
key 1024 tiff_tag_location 0 count 1 value_offset 1 - GTModelTypeGeoKey: ModelTypeProjected
key 3072 tiff_tag_location 0 count 1 value_offset 2227 - ProjectedCSTypeGeoKey: NAD83 / California zone 3 (ftUS)
key 3076 tiff_tag_location 0 count 1 value_offset 9003 - ProjLinearUnitsGeoKey: Linear_Foot_US_Survey
key 4099 tiff_tag_location 0 count 1 value_offset 9001 - VerticalUnitsGeoKey: Linear_Meter
LASzip compression (version 2.4r1 c2 50000): POINT10 2 GPSTIME11 2
reporting minimum and maximum for all LAS point record entries ...
X 27775000 27799999
Y 612225000 612249999
Z 4221 6435
intensity 10 62293
return_number 1 3
number_of_returns 1 3
edge_of_flight_line 0 0
scan_direction_flag 0 0
classification 1 6
scan_angle_rank 79 103
user_data 0 197
point_source_ID 1 1
gps_time 5880.963028 5886.739738
number of first returns: 263413
number of intermediate returns: 283
number of last returns: 263370
number of single returns: 249493
overview over number of returns of given pulse: 249493 27232 848 0 0 0 0
histogram of classification of points:
17553 unclassified (1)
180868 ground (2)
37030 high vegetation (5)
42122 building (6)
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