geocat.comp.gradient._arc_lon_wgs84#
- geocat.comp.gradient._arc_lon_wgs84(lon, lat)#
The arc length calculation for the wgs84 ellipsoid at a longitude uses a taylor series from.
\[arclon = lon \cdot \cos(lat) \cdot \sqrt{a^2 \cdot \cos(lat)^2+b^2 \cdot \sin(lat)^2}\]This returns the distance from the Greenwich Meridian to a given latitude This is accurate to within floating point error.
Note
This doesn’t need to be a taylor series, though the taylor series is faster and a needed step for the _arc_lat_wgs84 function to avoid the elliptic integral
- Parameters
lon (
numpy.ndarray
,xarray.DataArray
) – 2-dimensional dataset, of orthographic longitude coordinateslat (
numpy.ndarray
,xarray.DataArray
) – 2-dimensional dataset, of orthographic latitude coordinates
- Returns
gradients (
list
ofnumpy.ndarray
,list
ofxarray.DataArray
) – Longitudinal arc from Prime Meridian calculated using th WGS84 geoid.
See also
Related NCL Functions: grad_latlon_cfd, gradsf, gradsg