gmf - Calculating the "global mapping function" (GMF).
Add here a paragraph of the function description. Other paragraph can be added
Boehm, J., A.E. Niell, P. Tregoning, H. Schuh (2006), Global Mapping Functions (GMF): A new empirical mapping function based on numerical weather model data, Geophphysical Research Letters, Vol. 33, L07304, doi:10.1029/2005GL025545.
No warranty, there are no inputchecks.
(not matrix aware)