title | keywords | sidebar | permalink | summary | tags | toc | editdoc | |
---|---|---|---|---|---|---|---|---|
MakeEllipseCoord (Fortran) |
spherical harmonics software package, spherical harmonic transform, legendre functions, multitaper spectral analysis, fortran, Python, gravity, magnetic field |
mydoc_sidebar |
makeellipsecoord.html |
|
false |
fdoc |
Compute the coordinates of an ellipse placed at a given latitude and longitude.
call MakeEllipseCoord (coord
, lat
, lon
, dec
, a_theta
, b_theta
, cinterval
, cnum
, exitstatus
)
coord
: output, real*8, dimension(360/cinterval
, 2)
: The latitude (:,1) and longitude (:,2) coordinates of the ellipse in degrees.
lat
: input, real(dp)
: The latitude of the center of the ellipse in degrees.
lon
: input, real(dp)
: The longitude of the center of the ellipse in degrees.
dec
: input, real(dp)
: Rotation angle of the semi-major axis of the ellipse in degrees with respect to local north.
a_theta
: input, real(dp)
: The angular radius of the semi-major axis of the ellipse in degrees.
b_theta
: input, real(dp)
: The angular radius of the semi-minor axis of the ellipse in degrees.
cinterval
: optional, input, real(dp), default = 1
: Angular spacing in degrees of the output latitude and longitude points. If not present, the default is 1.
cnum
: optional, output, integer
: Number of elements in the output arrays.
exitstatus
: output, optional, integer
: If present, instead of executing a STOP when an error is encountered, the variable exitstatus will be returned describing the error. 0 = No errors; 1 = Improper dimensions of input array; 2 = Improper bounds for input variable; 3 = Error allocating memory; 4 = File IO error.
MakeEllipseCoord
will calculate the (lat, long) coordinates of an ellipse placed on a sphere at position (lat
, lon
). The semi-major and semi-minor axes, expressed in angular radii in degrees, are given by a_theta
and b_theta
, respectively. The semimajor axis of the ellipse is initially directed due north, and it is then rotated clockwise by the angle dec
. This is useful for plotting ellipses on geographic maps. The first index in the output vectors corresponds to the northern rotated semimajor axis, and subsequent points are arranged in a clockwise manner. Input and output units are in degrees.