def get_proj(ifile):
"""
MAP_PROJ - Model projection [1=Lambert, 2=polar stereographic,
3=mercator, 6=lat-lon] (required)
TRUELAT1 - required for MAP_PROJ = 1, 2, 3 (defaults to 0 otherwise)
TRUELAT2 - required for MAP_PROJ = 6 (defaults to 0 otherwise)
STAND_LON - Standard longitude used in model projection (required)
REF_LON, REF_LON - A reference longitude and latitude (required)
KNOWNI, KNOWNJ - The I and J locations of REF_LON and REF_LAT (required)
POLE_LAT - optional for MAP_PROJ = 6 (defaults to 90 otherwise)
POLE_LAT - optional for MAP_PROJ = 6 (defaults to 0 otherwise)
DX, DY - required for MAP_PROJ = 1, 2, 3 (defaults to 0 otherwise)
LATINC, LONINC - required for MAP_PROJ = 6 (defaults to 0 otherwise)
"""
projname = {
1: "lambert_conformal_conic",
2: 'polar_stereographic',
3: 'mercator'
}[ifile.MAP_PROJ]
var = ifile.createVariable(projname, 'i', ())
var.grid_mapping_name = projname
var.earth_radius = 6370000.
var.false_easting = 0
var.false_northing = 0
x0_from_cen = len(ifile.dimensions['west_east']) / 2 * ifile.DX
y0_from_cen = len(ifile.dimensions['south_north']) / 2 * ifile.DY
if projname == 'mercator':
var.longitude_of_projection_origin = ifile.STAND_LON
var.standard_parallel = ifile.TRUELAT1
elif projname == "lambert_conformal_conic":
var.standard_parallel = np.array([ifile.TRUELAT1, ifile.TRUELAT2])
var.longitude_of_central_meridian = ifile.STAND_LON
var.latitude_of_projection_origin = ifile.MOAD_CEN_LAT
elif projname == 'polar_stereographic':
var.straight_vertical_longitude_from_pole = ifile.STAND_LON
var.latitude_of_projection_origin = ifile.TRUELAT1
var.standard_parallel = ifile.MOAD_CEN_LAT
from PseudoNetCDF.coordutil import getproj4_from_cf_var
from mpl_toolkits.basemap import pyproj
projstr = getproj4_from_cf_var(var)
proj = pyproj.Proj(projstr)
gcx, gcy = proj(ifile.CEN_LON, ifile.CEN_LAT)
glx = gcx - x0_from_cen
gly = gcy - y0_from_cen
var.false_easting = -glx
var.false_northing = -gly
return projname
def getproj(self, withgrid=False, projformat='pyproj'):
from PseudoNetCDF.coordutil import getproj4_from_cf_var
gridmapping = self.variables['crs']
proj4str = getproj4_from_cf_var(gridmapping, withgrid=withgrid)
preserve_units = withgrid
if projformat == 'proj4':
return proj4str
elif projformat == 'pyproj':
import pyproj
# pyproj adds +units=m, which is not right for latlon/lonlat
if '+proj=lonlat' in proj4str or '+proj=latlon' in proj4str:
preserve_units = True
return pyproj.Proj(proj4str, preserve_units=preserve_units)
elif projformat == 'wkt':
import osr
srs = osr.SpatialReference()
# Imports WKT to Spatial Reference Object
srs.ImportFromProj4(proj4str)
srs.ExportToWkt() # converts the WKT to an ESRI-compatible format
return srs.ExportToWkt()
else:
raise ValueError('projformat must be pyproj, proj4 or wkt')