[pdal] Write and zip function based on PDAL

[Michael P. Gerlek]

> Thank you very much for the update, now both the reader and writer are
working. The workflow that I really want is:

> 1) Read an original las(a little bigger), 

What do you mean "a little bigger"?

> 2) Visualize the point cloud

There is a pcview application in pdal, but it is really only a sample app,
nothing useful for production work.

> 2) Do some filtering(vegetation or forest)

Is the las file already classified?  If so, that's an easy filter to write.

> 3) Write the points to a file

(working now)

> 4) compress the file

(working now) 

> 5) rasterize the file into a DEM(which I can used for hydrologic modeling)

We don't have DEM generation in pdal yet, but that is something we'd like to
have.  lastools has las2dem, but it is likely not open source.

> BTW, a powerful LiDAR viewer will be perfect, I tried the Lasview of
libLAS, it seems working very good, have you already implemented it?

libLAS doesn’t have a viewer as far as I know -- you probably mean the
viewer in lastools?  Here again, I'm not sure how much of that application
is open source.

-mpg