WIP: Interpolate missing Z values along a 3D line.
WIP: Interpolate missing Z values along a 3D line.

A work in progress, adapted from @Tomek's work at
http://gis.stackexchange.com/a/18655/108

in support of http://gis.stackexchange.com/questions/146997/how-to-interpolate-line-z-from-sparse-attribute-values

maphew/arcplus,maphew/arcplus,DougFirErickson/arcplus