[Liblas-devel] ECEF?

[Howard Butler]

On Mar 4, 2011, at 8:32 PM, Ben Discoe wrote:

> OK, my first question: how does one store points in ECEF coordinates?
> Specifically, how does one indicate in the header that the points are
> in ECEF?  liblas::SpatialReference seems to only talk about the usual
> geographic and projected CRSes.  In our case, the data is gathered and
> processed in ECEF, served as ECEF, and rendered on the client in ECEF.
> It would be sad to have to convert from ECEF to something like
> lat-lon or UTM, in order to write LAS, then have to convert back again
> on read.
> 
> If there is no explicit support in LAS or libLAS for ECEF, i suppose i
> could just write ECEF anyway, which would no doubt work for reading
> our own files - but then interoperability is lost.

Is there any way to describe ECEF using WKT?  If you're using libLAS 1.6+, it will prefer to use the WKT coordinate system records and you'll be able to at least describe the coordinate system the data are stored it.  

I haven't seen any LAS data in ECEF, or at least seen any coordinate system descriptions in LAS files that describe that in my time doing libLAS.  It's quite common for LAS data to have no coordinate system information at all, however.  Think shapefiles, with all the misery that entails :)

As an aside, I have written up some language for WKT for the next LAS 1.4 specification that I hope is adopted.  See http://liblas.org/development/wkt.html for more information, and I'd be interested in any feedback folks might have.

Another aside is that E57 explicitly supports polar coordinate systems http://libe57.org/  You might look there for options too.

Howard