makeellipsecoord.3

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.TH "makeellipsecoord" "1" "2021-02-15" "Fortran 95" "SHTOOLS 4.11"
.hy
.SH MakeEllipseCoord
.PP
Compute the coordinates of an ellipse placed at a given latitude and
longitude.
.SH Usage
.PP
call MakeEllipseCoord (\f[V]coord\f[R], \f[V]lat\f[R], \f[V]lon\f[R],
\f[V]dec\f[R], \f[V]a_theta\f[R], \f[V]b_theta\f[R],
\f[V]cinterval\f[R], \f[V]cnum\f[R], \f[V]exitstatus\f[R])
.SH Parameters
.TP
\f[V]coord\f[R] : output, real(dp), dimension(360/\f[V]cinterval\f[R], 2)
The latitude (:,1) and longitude (:,2) coordinates of the ellipse in
degrees.
.TP
\f[V]lat\f[R] : input, real(dp)
The latitude of the center of the ellipse in degrees.
.TP
\f[V]lon\f[R] : input, real(dp)
The longitude of the center of the ellipse in degrees.
.TP
\f[V]dec\f[R] : input, real(dp)
Rotation angle of the semi-major axis of the ellipse in degrees with
respect to local north.
.TP
\f[V]a_theta\f[R] : input, real(dp)
The angular radius of the semi-major axis of the ellipse in degrees.
.TP
\f[V]b_theta\f[R] : input, real(dp)
The angular radius of the semi-minor axis of the ellipse in degrees.
.TP
\f[V]cinterval\f[R] : optional, input, real(dp), default = 1
Angular spacing in degrees of the output latitude and longitude points.
If not present, the default is 1.
.TP
\f[V]cnum\f[R] : optional, output, integer(int32)
Number of elements in the output arrays.
.TP
\f[V]exitstatus\f[R] : output, optional, integer(int32)
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.
.SH Description
.PP
\f[V]MakeEllipseCoord\f[R] will calculate the (lat, long) coordinates of
an ellipse placed on a sphere at position (\f[V]lat\f[R],
\f[V]lon\f[R]).
The semi-major and semi-minor axes, expressed in angular radii in
degrees, are given by \f[V]a_theta\f[R] and \f[V]b_theta\f[R],
respectively.
The semimajor axis of the ellipse is initially directed due north, and
it is then rotated clockwise by the angle \f[V]dec\f[R].
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.
.SH See also
.PP
makecirclecoord