Computing cartesian and geographical coordinates for polar data

In [1]:
import numpy as np
import wradlib.georef as georef
import wradlib.io as io
import wradlib.util as util
import warnings
warnings.filterwarnings('ignore')

Read the data

Here, we use an OPERA hdf5 dataset.

In [2]:
filename = 'hdf5/20130429043000.rad.bewid.pvol.dbzh.scan1.hdf'
filename = util.get_wradlib_data_file(filename)
pvol = io.read_opera_hdf5(filename)

Count the number of datasets

In [3]:
ntilt = 1
for i in range(100):
    try:
        pvol["dataset%d/what" % ntilt]
        ntilt += 1
    except Exception:
        ntilt -= 1
        break

Define radar location and scan geometry

In [4]:
nrays = int(pvol["dataset1/where"]["nrays"])
nbins = int(pvol["dataset1/where"]["nbins"])
rscale = int(pvol["dataset1/where"]["rscale"])
coord = np.empty((ntilt, nrays, nbins, 3))
for t in range(ntilt):
    elangle = pvol["dataset%d/where" % (t + 1)]["elangle"]
    coord[t, ...] = georef.sweep_centroids(nrays, rscale, nbins, elangle)
# ascale = math.pi / nrays
sitecoords = (pvol["where"]["lon"], pvol["where"]["lat"],
              pvol["where"]["height"])
print(coord.shape)
(5, 360, 960, 3)

Retrieve azimuthal equidistant coordinates and projection

In [5]:
coords, proj_radar = georef.spherical_to_xyz(coord[..., 0],
                                             np.degrees(coord[..., 1]),
                                             coord[..., 2], sitecoords)
test = coords[0, 90, 0:960:60, 0]
print(test)
[1.24984800e+02 1.51230048e+04 3.01206529e+04 4.51178353e+04
 6.01144584e+04 7.51104287e+04 9.01056525e+04 1.05100036e+05
 1.20093487e+05 1.35085910e+05 1.50077213e+05 1.65067302e+05
 1.80056083e+05 1.95043465e+05 2.10029352e+05 2.25013652e+05]

Retrieve geographic coordinates (longitude and latitude)

Using convenience function spherical_to_proj.

In [6]:
lonlatalt = georef.spherical_to_proj(coord[..., 0],
                                     np.degrees(coord[..., 1]),
                                     coord[..., 2], sitecoords)
test = lonlatalt[0, 90, 0:960:60, 0]
print(test)
[5.50734017 5.71615328 5.92494778 6.13371911 6.34246274 6.55117413
 6.75984874 6.96848204 7.17706951 7.38560664 7.5940889  7.8025118
 8.01087084 8.21916154 8.42737941 8.63552   ]

Using reproject

In [7]:
lonlatalt1 = georef.reproject(coords, projection_source=proj_radar,
                             projection_target=georef.get_default_projection())

test = lonlatalt1[0, 90, 0:960:60, 0]
print(test)
[5.50734017 5.71615328 5.92494778 6.13371911 6.34246274 6.55117413
 6.75984874 6.96848204 7.17706951 7.38560664 7.5940889  7.8025118
 8.01087084 8.21916154 8.42737941 8.63552   ]