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curve2mask.1
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curve2mask.1
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.\" Automatically generated by Pandoc 2.5
.\"
.TH "curve2mask" "1" "2017\-11\-28" "Fortran 95" "SHTOOLS 4.4"
.hy
.SH Curve2Mask
.PP
Given a set of latitude and longitude coordinates representing a closed
curve, output a gridded binary mask.
.SH Usage
.PP
call Curve2Mask (\f[C]mask_dh\f[R], \f[C]n\f[R], \f[C]sampling\f[R],
\f[C]profile\f[R], \f[C]nprofile\f[R], \f[C]np\f[R],
\f[C]centralmeridian\f[R], \f[C]exitstatus\f[R])
.SH Parameters
.TP
.B \f[C]dh_mask\f[R] : output, integer, dimension (\f[C]n\f[R], \f[C]n\f[R]*\f[C]sampling\f[R])
A Driscoll and Healy (1994) sampled grid describing the concentration
region R.
All elements on output will either be 1 (for inside the concentration
region) or 0 (for outside R).
.TP
.B \f[C]n\f[R] : input, integer
The number of latitudinal samples in \f[C]dh_mask\f[R].
The effective spherical harmonic bandwidth of this grid is
\f[C]L=n/2\-1\f[R].
.TP
.B \f[C]sampling\f[R] : input, integer
For 1, \f[C]dh_mask\f[R] has \f[C]n\f[R] x \f[C]n\f[R] samples.
For 2, \f[C]dh_mask\f[R] has \f[C]n\f[R] x \f[C]2n\f[R] samples.
.TP
.B \f[C]profile\f[R] : input, real*8, dimension (\f[C]nprofile\f[R], 2)
List of latitude (:,1) and longitude (:,2) coordinates in degrees
specifying a single closed curve.
.TP
.B \f[C]nprofile\f[R] : input, integer
The number of coordinates in the curve \f[C]profile\f[R].
.TP
.B \f[C]np\f[R] : input, integer
The value of the returned mask at the North pole (90N, 0E).
If the North pole is outside of the concentration region, set this to 0;
if it is inside the concentration region, set this to 1.
.TP
.B \f[C]centralmeridian\f[R] : input, optional, integer, default = 0
If 1, the curve is assumed to pass through the central meridian: passing
from < 360 degrees to > 0 degrees.
The curve makes a complete circle about the planet in longitude.
.TP
.B \f[C]exitstatus\f[R] : 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.
.SH Description
.PP
\f[C]Curve2Mask\f[R] will take a list of latitude and longitude
coordinates that represent a single closed curve, and output a mask
\f[C]mask_dh\f[R] that contains 1s and 0s where the grid nodes are
inside and outside of the curve, respectively.
\f[C]mask_dh\f[R] must be sampled according to the Driscoll and Healy
(1994) sampling theorem with \f[C]n\f[R] samples in latitude, and either
possess \f[C]n\f[R] samples in longitude (\f[C]sampling=1\f[R]) or
\f[C]2n\f[R] samples in longitude (\f[C]sampling=2\f[R]).
It is necessary to specify a single point as being inside or outside of
the curve, and for this the value at the North pole (90N, 0E) must be
specified as either 0 or 1.
.PP
This routine saves the three\-term recursion factors and square roots of
the integers the first time being called.
If subsequent calls possess the same value of \f[C]lmax\f[R], these will
not be recomputed.
If you wish to deallocate this memory, which is an array of length
\f[C](lmax+1)*(lmax+2)\f[R], recall this routine with
\f[C]lmax=\-1\f[R].
.SH References
.PP
Driscoll, J.R.
and D.M.
Healy, Computing Fourier transforms and convolutions on the 2\-sphere,
Adv.
Appl.
Math., 15, 202\-250, 1994.
.SH See also
.PP
shreturntapersmap, computedmap