You want urn:ogc:def:crs:EPSG::26912 from the GML link on spatialreference.org. GML uses the URN syntax for describing coordinate systems.
Alternatively, you could specify
"crs": {
"type": "link",
"properties": {
"href": "http://spatialreference.org/ref/epsg/26912/esriwkt/",
"type": "esriwkt"
}
}
or
"crs": {
"type": "link",
"properties": {
"href": "http://spatialreference.org/ref/epsg/26912/proj4/",
"type": "proj4"
}
}
The GeoJSON spec is not being silly here. It is trying to take advantage of the most precisely specified coordinate system description specification. That is most likely the URN-style GML SRS description.
I would agree that consumption of this is not so widely available. That's why the alternative derferenceable "link" syntax is available, and I explicitly intended it to link to spatialreference.org links. I know proj4js takes advantage of this feature of the GeoJSON specification. You might look there for inspiration.
Yes, geographic coordinates and DEM is bad, depending upon your software of course; several Esri functions don't work properly in geographic coordinates. Your point spacing becomes tiny and so does your cell size.
I believe las2las will reproject LiDAR data based on the readme. This data is supplied in geographic coordinates possibly because it needs to cover a very large area and a projected coordinate system would not be a SRID coordinate system to cover that.
I definitely recommend projecting geographic las to projected las or tools like las2dem probably wont produce intended results, possibly due to small number rounding.
Another case to reproject LiDAR data is when you are supplied las files in different coordinate systems - pick one and project the others.
Best Answer
I looked for an already existing question, but wasn't able to find one.
GRS80 is an ellipsoid (spheroid in Esri software), not an actual geodetic datum or coordinate reference system. If Esri software is given data that only has a grs80 and no other datum information, we'll build a GRS80-based geographic coordinate [reference] system.
Because it's not an actual GeoCRS (datum), there are no available transformations for it.
You could assume that they're all actually NAD 1983, and redefine the coordinate systems to use the standard NAD 1983 geographic coordinate system. Or you could create a custom geographic transformation using the tool. You could either use all zeroes for the parameter values and pick the geocentric translation method.