[pdal] calculate CHM

[Luca Delucchi]

Hi devs,

I'm trying to calculate CHM using filters.programmable but I have some
problems with points close to the DTM border and so I'm not able to
update the Z value for these points.

My idea is to use  filters.predicate to remove these point outside the
DTM and later run the filters.programmable, but I don't know
concatenate the two filter, it seems each filter neeeds a Reader tag
and I don't know how to tell to second filter to read the output of
the first.

Should I use two Writer tag?

Thanks

-- 
ciao
Luca

http://gis.cri.fmach.it/delucchi/
www.lucadelu.org