Conformal Map Functions (CMAPF)

What are the CMAPF routines?

The CMAPF routines are libraries of tools - functions and subroutines that allow meteorological model programs to be independent of the choice of map projection on which their model is based. Most models are based on a rectangular lattice of mesh points drawn on some specific map, the choice of which depends on a number of considerations, including the size and location of the region to be modeled. The geometry of the map introduces subtle changes in the equations describing the physics of the model, whose terms are provided by calls to these subroutines.

When a model requires input data from another source, which was gridded on some other mesh drawn on some other map projection, the CMAPF routines can accomplish the translation from one to the other, since they can work with several projections concurrently.

What Map Projections do the CMAPF routines deal with?

There are two versions of the CMAPF routines, version 1.0 and 2.0. Version 1.0 covers the standard conformal map projections centered at the North and South Pole, namely the Polar Stereographic, the Mercator, and the Lambert Conformal projections.

Version 2.0 covers the same set of conformal routines, but instead of being restricted to centering on the poles, they may be centered on an equatorial point (Transverse Mercator) or on any other point (Oblique Stereographic).

In what language can I access the CMAPF routines?

The CMAPF function libraries were written in FORTRAN and in C. Both versions are essentially the same, except for minor variations to accommodate the differences in language.

Where can I find out more about the CMAPF functions?

Version 1.0 is described more fully in an article, Conformal Map Transformations for Meteorological Modelers, by Albion D. Taylor, published in the February, 1997 issue of Computers and Geosciences (v23, no 1). An FAQ is also available here.

How do I use the CMAPF libraries?

Instructions for using the routines are summarized in the C-version here and in the FORTRAN-version here

How do I obtain the CMAPF libraries?

Version 1.0 (13.6 Kb, gz) is available for download here, or from the Computers and Geosciences site.

Version 2.0 (21,4 Kb, gz), is now available here. This version (also known as the Dmapf routines) adds Oblique and Transverse projections to the normal projections covered by version 1.0. That is, projections can be oriented around any diameter of the Earth, rather than just the Polar axis, which can be convenient for smaller scale local grids. Instructions on the use of the Dmapf routines is available for both the C-language and the FORTRAN language.

In addition, several display utility routines using Dmapf can be installed on 32-bit Windows platforms (Windows 95 and later).