I updated an old code, Interpolation_auto.F, to a new and revamped version, DEM2GRD.F90. The utility takes in a Digital Elevation Model (DEM) and interpolates it onto an unstructured finite element mesh using the cell-area averaging (CAA) algorithm published in Bilskie & Hagen (2013).
An example input file can be found here.
I also put together a brief User Manual here.