text: Title: Possible bug plotting CSAPR-2 HSRHIs
  Body: In plotting CSAPR-2 HSRHIs from CACTI, I am having issues with plotting RHIs at 90° azimuth with `display.plot_rhi()`.  This behavior is repeatable amongst many files, but only at this azimuth angle.  Seems like a geometry issue.  
  Example is here:
  ![junk](https://user-images.githubusercontent.com/3288592/55437035-c1e1f100-5552-11e9-9ccb-9287bac036d7.png)
  Interestingly, `radar.get_gate_x_y_z(sweep=3)` seems to extract ok values:
  ![get_gate](https://user-images.githubusercontent.com/3288592/55436859-3c5e4100-5552-11e9-8dcd-21cb5b3a6099.png)
  I'll keep digging...