There is a great, free contour mapping program called gmt
GMTSYSTEM(l) MISC. REFERENCE MANUAL PAGES GMTSYSTEM(l)
gmtsystem - A generic data processing and display software
The GMT-SYSTEM is a public domain software package that can
be used to manipulate and display 2-dimensional (e.g.,
time-series or (x,y) series) or 3-dimensional data sets
(e.g., (x,y,z) grids). The processing and display routines
within the GMT- SYSTEM are completely general and will han-
dle any (x,y) or (x,y,z) data as input. Most of the pro-
grams will produce some kind of output, which falls into
four categories. Some of the programs may produce more than
one of these types of output:
1. 1-D Tables - For example, a (x,y) series may be fil-
tered and the filtered values are output. These files
are in the ASCII format and can be edited with any text
2. 2-D grdfiles - Programs that grid data will typically
read (x,y,z) ASCII tables and create a 2-D equidistant
table which is stored in a binary file format. These
files are called grd-files and cannot be edited with
ordinary text editors.
3. PostScript - The plotting programs all use the
PostScript page description language to define plots.
These commands are stored as ASCII text and can be
edited should you want to customize the plot beyond the
options available through the programs themselves.
4. Reports - Several programs read ASCII tables or binary
grd-files and report statistics and other information.
Such text is written to the standard error stream and
can therefore be separated from ASCII table output.
You can get it from pub/gmt on kiawe.soest.hawaii.edu (Get all the GMT_*.tar.Z
files plus the new netcdf.tar.Z).