Mapping Toolbox™

rcurve - Radii of curvature of ellipsoid

Syntax

r = rcurve(ellipsoid,lat)
r = rcurve('parallel',ellipsoid,lat)
r = rcurve(ellipsoid,lat,units)
r = rcurve('meridian',ellipsoid,lat,units)
r = rcurve('transverse',ellipsoid,lat,units)

r = rcurve(ellipsoid,lat) and r = rcurve('parallel',ellipsoid,lat) return the parallel radius of curvature at the latitude lat for a given elliptical definition, where ellipsoid is a two-element ellipsoid vector. This is the radius of the small circle encompassing the ellipsoid at the given latitude. The radius is a distance in units consistent with the semimajor axis, the first element of ellipsoid.

r = rcurve(ellipsoid,lat,units) specifies the units of the input lat, where units is any valid angle units string. The default is 'degrees'.

r = rcurve('meridian',ellipsoid,lat,units) returns the meridianal radius, which is the radius of curvature at the latitude lat for the ellipse described by a meridian on the ellipsoid.

r = rcurve('transverse',ellipsoid,lat,units) returns the transverse radius, which is the radius of a curve described by the intersection of the ellipsoid with a plane normal to the surface of the ellipsoid at the latitude lat.

Examples

The radii of curvature of the default ellipsoid at 45º, in kilometers:

r = rcurve('transverse',almanac('earth','ellipsoid','km'),...
            45,'degrees')

r =
   6.3888e+03

r = rcurve('meridian',almanac('earth','ellipsoid','km'),...
            45,'degrees')

r =
   6.3674e+03

r = rcurve('parallel',almanac('earth','ellipsoid','km'),...
            45,'degrees')

r =
   4.5024e+03

See Also

rsphere

rad2km, rad2nm, rad2sm

readfields