[pdal] Fixing the topology of the hexagon coverage from density

[Jukka Rahkonen]

Hi,

I noticed that the vertices of the hexagon cells that "pdal density" 
writes out do not match exactly. It means that it is not easy to union 
the output into one polygon with GIS tools. The issue can be fixed by 
reducing the precision of coordinates with the PostGIS ST_Snap or 
similar tool. With a projected CRS it was enough to round the 
coordinates into 5 decimal places. It might be good to have a coordinate 
rounding option directly in the density tool.

-Jukka Rahkonen-