Display method for plotting locations of azimuth angles

[jjhelmus]

As suggested by @nguy on the Py-ART mailing list a method for plotting a line along a particular azimuthal angle on top of a plot of a PPI would make a good addition to Py-ART.

[gamaanderson]

ideally such a line should not be a strait line, but slightly curved depending on the map projection.

[jjhelmus]

Agreed, although only on maps. I think the line should be straight when generated with RadarDisplay. Would transforming the Cartesian coordinates of the line into Geographic (latitude and longitude) points would results in a curved line.

[nguy]

I think a straigh line is the way to go with RadarDisplay. The code in pyart.util.xsect.cross_section_ppi should do a lot of the work for this, right? The Cartesian and geographic (fed back into the basemap instance) should be able to be used for the line if I'm thinking of this correctly.

[jjhelmus]

The antenna_to_cartesian function will work for the RadarDisplay. For plotting on maps the best solution is probably to also transforms these to geographic coordinate, I have to think about this a bit more.

[jjhelmus]

Unless I'm not understanding the use of this function, I don't think pyart.util.xsect.cross_section_ppi will be of use here.

[nguy]

Not the function, I was just floating through some of the code. I was also thinking of having the ability to select a line for cross-sectioning, like can be done here in the future, which is why I was rummaging through that particular code.

Not sure if this would be a Py-ART or ARTview thing though.

[nguy]

I should say the GUI part would obviously be ARTview, but where do we put the code under the hood?

[jjhelmus]

Scott and I were talking a few days ago about adding methods to the Radar and Grid class which return the indices for the nearest gate or point to a set of coordinates (either x, y, z or longitude, latitude and altitude). I think with methods like this, lookup of the data would be quite straightforward. I opened an issue (#476) for this feature.

[jlpippitt]

I know this is an old post and you may have implemented new code. I was able to plot azimuths doing the following.

dtor = math.pi/180.0
max_range=150.0
maxrange_meters = max_range * 1000.
meters_to_lat = 1. / 111177.
meters_to_lon =  1. / (111177. * math.cos(radar_lat * dtor))

for azi in range(0,360,30):
        azimuth = 90. - azi
        dazimuth = azimuth * dtor
        lon_maxrange = radar_lon + math.cos(dazimuth) * meters_to_lon * maxrange_meters
        lat_maxrange = radar_lat + math.sin(dazimuth) * meters_to_lat * maxrange_meters
        display.plot_line_geo([radar_lon, lon_maxrange], [radar_lat, lat_maxrange],line_style='k-',lw=0.5)

[zssherman]

Thanks @jlpippitt ! I can't remember if this was ever added, but would be great to add to an example or function if it never was. I'll look into that.