def dem_degree2meter(demfile):
"""
compute the spatial resolution in meters for a DEM with WGS84 degree coordinates.
Parameters
----------
demfile: str
the DEM file
Returns
-------
tuple
(posting_east, posting_north)
See Also
--------
spatialist.auxil.haversine
"""
with Raster(demfile) as ras:
res_lon, res_lat = ras.res
lat = (ras.geo['ymin'] + ras.geo['ymax']) / 2
lon = (ras.geo['xmin'] + ras.geo['xmax']) / 2
post_north = haversine(lat, lon, lat + res_lat, lon)
post_east = haversine(lat, lon, lat, lon + res_lon)
return post_east, post_north
def ovs(parfile, targetres):
"""
compute DEM oversampling factors for a target resolution in meters
Parameters
----------
parfile: str
a GAMMA DEM parameter file
targetres: int or float
the target resolution in meters
Returns
-------
tuple of float
the oversampling factors for latitude and longitude
"""
# read DEM parameter file
dempar = ISPPar(parfile)
# extract coordinates and pixel posting of the DEM
if hasattr(dempar, 'post_north'):
post_north, post_east = [
abs(float(x)) for x in [dempar.post_north, dempar.post_east]
]
else:
res_lat, res_lon = [
abs(float(x)) for x in [dempar.post_lat, dempar.post_lon]
]
# compute center coordinate
lat = float(dempar.corner_lat) - (res_lat * (dempar.nlines // 2))
lon = float(dempar.corner_lon) + (res_lon * (dempar.width // 2))
# convert DEM resolution to meters
post_north = haversine(lat, lon, lat + res_lat, lon)
post_east = haversine(lat, lon, lat, lon + res_lon)
# compute resampling factors for the DEM
ovs_lat = post_north / targetres
ovs_lon = post_east / targetres
return ovs_lat, ovs_lon
def test_haversine():
assert haversine(50, 10, 51, 10) == 111194.92664455889
