
NCL > Application examples > Basic examples
MapPlot example 3
How to use masking and overlays with maps
This mapping example was created using HLU C and HLU FORTRAN library calls and NCL. It demonstrates how to use masking and overlays to show a map and a contour plot together. The names of the source files for this example are mp03c.c, mp03f.f, and mp03n.ncl.

Discussion
This module discusses how to create this example using HLU function
calls and a resource file. The program demonstrates how to create a MapPlot
object and set the mask area specifiers to be used when overlaying the
ContourPlot object. The resource file used in this example is called mp03.res.
A detailed discussion of how this example works appears in its source code.
Creating the plot using HLUs
The HLU C program that generates this plot is called mp03c.c.
Creating the plot using HLU FORTRAN library calls
The HLU FORTRAN program that generates this plot is called mp03f.f.
Creating the plot using NCL
The NCL script that generates this plot is called mp03n.ncl.
The data
The contour data for this plot was generated by the subroutine GENDAT. This routine is located in the source file for the C and FORTRAN versions of this example. The NCL version reads the data from an external file called mp03n.asc.
How to run this example
The examples are installed in the following locations:
- $NCARG_ROOT/lib/ncarg/hluex/mapplot/mp03c.c
- $NCARG_ROOT/lib/ncarg/hluex/mapplot/mp03f.f
- $NCARG_ROOT/lib/ncarg/nclex/mapplot/mp03n.ncl