Pierre, > I just added code to PerfectTIN to read the variable-length records of a LAS > file. I found a WKT record in a square of West Virginia terrain, with no > line feeds; I added line feeds and indentation and attached it. The other > point clouds do not have variable-length records. I'd like to heed the WKT > units when loading a point cloud, if there is a WKT. > > I'm also working on a program called Wolkenbase (not public yet) which will > separate ground from non-ground in a point cloud. If you load a point cloud > with no unit information, I'd like to add a WKT that indicates only the unit > and nothing else. What would that look like?
As far as I know, you can't create a CRS WKT with just unit information. The most minimal content that validates the WKT1 grammar would be something like: LOCAL_CS["unspecified CRS", LOCAL_DATUM["unspecified datum",2000], UNIT["metre",1, AUTHORITY["EPSG","9001"]], AXIS["Easting",EAST], AXIS["Northing",NORTH]] > Do you have code to parse and manipulate WKT? The WKT is in a std::string. Yes, PROJ >= 6 has support for parsing and creating WKT in several versions of the WKT standard. See proj_create_from_wkt() at https://proj.org/development/reference/functions.html, and all other proj_XXXX getters. For creation of WKT, you might need the more advanced functions of https://github.com/OSGeo/PROJ/blob/master/src/proj_experimental.h , before exporting with proj_as_wkt() GDAL's OGRSpatialReference class showcases using number of the above mentionned PROJ functions: https://github.com/OSGeo/gdal/blob/master/gdal/ogr/ogrspatialreference.cpp You may also look at PDAL that uses PROJ and/or GDAL underneath to deal with LAS CRS: https://pdal.io/tutorial/las.html#spatial-reference-system Even -- Spatialys - Geospatial professional services http://www.spatialys.com
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