makegrid2d.1

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.TH "makegrid2d" "1" "2018\-01\-30" "Fortran 95" "SHTOOLS 4.2"
.hy
.SH MakeGrid2D
.PP
Create a 2D cylindrical map of arbitrary grid spacing from a set of
spherical harmonic coefficients.
.SH Usage
.PP
call MakeGrid2D (\f[C]grid\f[], \f[C]cilm\f[], \f[C]lmax\f[],
\f[C]interval\f[], \f[C]nlat\f[], \f[C]nlong\f[], \f[C]norm\f[],
\f[C]csphase\f[], \f[C]f\f[], \f[C]a\f[], \f[C]north\f[],
\f[C]south\f[], \f[C]east\f[], \f[C]west\f[], \f[C]dealloc\f[],
\f[C]exitstatus\f[])
.SH Parameters
.TP
.B \f[C]grid\f[] : output, real*8, dimension (180/\f[C]interval\f[]+1, 360/\f[C]interval\f[]+1)
A 2D equally spaced map of the input spherical harmonic coefficients
\f[C]cilm\f[].
The array is in raster format with upper\-left and lower\-right
coordinates of (90 N, 0 E) and (90 S, 360 E), respectively.
.RS
.RE
.TP
.B \f[C]cilm\f[] : input, real*8, dimension (2, \f[C]lmax\f[]+1, \f[C]lmax\f[]+1)
The real spherical harmonic coefficients to be expanded in the space
domain.
The coefficients \f[C]C1lm\f[] and \f[C]C2lm\f[] refer to the cosine
(\f[C]Clm\f[]) and sine (\f[C]Slm\f[]) coefficients, respectively, with
\f[C]Clm=cilm(1,l+1,m+1)\f[] and \f[C]Slm=cilm(2,l+1,m+1)\f[].
.RS
.RE
.TP
.B \f[C]lmax\f[] : input, integer
The maximum spherical harmonic degree of the coefficients \f[C]cilm\f[]
used when calculating the grid.
.RS
.RE
.TP
.B \f[C]interval\f[] : input, real*8
The latitudinal and longitudinal spacing of \f[C]grid\f[].
.RS
.RE
.TP
.B \f[C]nlat\f[] : output, integer
The number of latitudinal samples.
Both 90 N and 90 S are included.
.RS
.RE
.TP
.B \f[C]nlong\f[] : output, integer
The number of longitudinal samples.
Both 0 and 360 E are included.
.RS
.RE
.TP
.B \f[C]norm\f[] : input, optional, integer, default = 1
1 (default) = 4\-pi (geodesy) normalized harmonics; 2 = Schmidt
semi\-normalized harmonics; 3 = unnormalized harmonics; 4 = orthonormal
harmonics.
.RS
.RE
.TP
.B \f[C]csphase\f[] : input, optional, integer, default = 1
1 (default) = do not apply the Condon\-Shortley phase factor to the
associated Legendre functions; \-1 = append the Condon\-Shortley phase
factor of (\-1)^m to the associated Legendre functions.
.RS
.RE
.TP
.B \f[C]f\f[] : input, optional, real*8
The flattening of the reference ellipoid that is subtracted from the
function.
This is given by (\f[C]R_equator\-R_pole)/R_equator\f[].
The semi\-major axis \f[C]a\f[] (i.e., \f[C]R_equator\f[]) must be
specified for this calculation.
.RS
.RE
.TP
.B \f[C]a\f[] : input, optional, real*8
The semi\-major axis of the reference ellispoid that is subtracted from
the function.
The flattening \f[C]f\f[] must be specified for this calculation.
.RS
.RE
.TP
.B \f[C]north\f[] : input, real*8, optional, default = 90
The maximum latitude of the output raster grid, in degrees.
The default is 90 degrees.
.RS
.RE
.TP
.B \f[C]south\f[] : input, optional, real*8, default = \-90
The minimum latitude of the output raster grid, in degrees.
The default is \-90 degrees.
.RS
.RE
.TP
.B \f[C]east\f[] : input, optional, real*8, default = 360
The maximum longitude of the output raster grid, in degrees.
The default is 360 degrees.
.RS
.RE
.TP
.B \f[C]west\f[] : input, optional, real*8, default = 0
The minimum longitude of the output raster grid, in degrees.
The default is 0 degrees.
.RS
.RE
.TP
.B \f[C]dealloc\f[] : input, optional, integer, default = 0
0 (default) = Save variables used in the external Legendre function
calls.
(1) Deallocate this memory at the end of the funcion call.
.RS
.RE
.TP
.B \f[C]exitstatus\f[] : 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.
.RS
.RE
.SH Description
.PP
\f[C]MakeGrid2D\f[] will create a 2\-dimensional cylindrical map,
equally spaced in (geocentric) latitude and longitude, from a set of
input spherical harmonic coefficients.
The output grid is in raster format possessing upper\-left and
lower\-right coordinates of (90 N, 0 E) and (90 S, 360 E), repsectively.
If the optional parameters \f[C]north\f[], \f[C]south\f[], \f[C]east\f[]
and \f[C]west\f[] are specified, then the output grid will possess
upper\-left and lower\-right coordinates of (\f[C]north\f[],
\f[C]west\f[]) and (\f[C]south\f[], \f[C]east\f[]), repsectively.
The employed spherical harmonic normalization and Condon\-Shortley phase
convention can be set by the optional arguments \f[C]norm\f[] and
\f[C]csphase\f[]; if not set, the default is to use geodesy 4\-pi
normalized harmonics that exclude the Condon\-Shortley phase of (\-1)^m.
.PP
If the optional arguments \f[C]f\f[] and \f[C]a\f[] are specified, the
output function will be referenced to an ellipsoid with flattening
\f[C]f\f[] and semimajor axis \f[C]a\f[].
The normalized legendre functions are calculated in this routine using
the scaling algorithm of Holmes and Featherstone (2002), which are
accurate to about degree 2800.
The unnormalized functions are accurate only to about degree 15.
.SH References
.PP
Holmes, S.
A., and W.
E.
Featherstone, A unified approach to the Clenshaw summation and the
recursive computation of very high degree and order normalised
associated Legendre functions, J.
Geodesy, 76, 279\-299, 2002.
.SH See also
.PP
makegriddh, makegriddhc, makegridglq, makegridglqc, makegravgriddh,
makemaggriddh