ARM-DOE/pyart — pull request #134 by scollis (2014-03-24 19:12:05+00:00)
Title: Fix map background

I have added an example but need Jonathan to run doc generation on it.. Uses NSA CF file from ASR tutorial as example..

A few enhancements to PPI plotting with map backgrounds, specifically cross hairs, labels and range rings.. Underlying routines can also be used to plot things like aircraft tracks or other shapes..
![nsa](https://f.cloud.github.com/assets/825351/2503974/118b43c2-b388-11e3-85e4-93562ec0e6a3.png)