GRDPROJECT
Section: Misc. Reference Manual Pages (l)
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NAME
grdproject - Forward and Inverse map transformation of 2-D grd files
SYNOPSIS
grdproject in_grdfile -Jparameters -Rwest/east/south/north[r]
[ -Ddx[m|c][/dy[m|c]] ] [ -Edpi ] [ -F ] [ -Gout_grdfile ] [ -I ]
[ -Nnx/ny ] [ -Ssearch_radius ] [ -V ]
DESCRIPTION
grdproject will do one of two things depending whether -I has been set. If set, it
will transform a gridded data set from a rectangular coordinate system onto a geographical
system by resampling the surface at the new nodes. If not set, it will project a geographical
gridded data set onto a rectangular grid. The new nodes are filled based on a simple weighted
average of nearby points. Aliasing is avoided by using sensible values for the search_radius.
The new node spacing may be determined in one of several ways by specifying the grid spacing,
number of nodes, or resolution. Nodes not constrained by input data are set to NaN.
No space between the option flag and the associated arguments. Use upper case for the
option flags and lower case for modifiers.
- in_grdfile
-
2-D binary grd file to be transformed.
#include "explain_-j.txt"
#include "explain_-R.txt"
OPTIONS
- -D
-
Set the grid spacing for the new grid. Append m for minutes, c for seconds.
- -E
-
Set the resolution for the new grid in dots pr inch.
- -F
-
Force pixel registration [Default is grid registration].
- -G
-
Specify the name of the output netCDF grd file.
- -I
-
Do the Inverse transformation, from rectangular to geographical.
- -N
-
Set the number of grid nodes in the new grid.
- -S
-
Set the search radius for the averaging procedure [Default avoids aliasing].
#include "explain_-V.txt"
EXAMPLES
To transform the geographical grid dbdb5.grd onto a pixel Mercator grid at 300 dpi, run
grdproject dbdb5.grd -R20/50/12/25 -Jm0.25 -E300 -F
-Gdbdb5_merc.grd
To inversely transform the file topo_tm.grd back onto a geographical grid try
grdproject topo_tm.grd -R-80/-70/20/40 -Jt-75/1:500000 -I -D5m -V -Gtopo.grd
RESTRICTIONS
The boundaries of a projected (rectangular) data set will not necessarily give rectangular
geographical boundaries (Mercator is one exception). In those cases some nodes may be unconstrained (set to NaN).
To get a full grid back, your input grid may have to cover a larger area than you are interrested in.
SEE ALSO
gmt, gmtdefaults, mapproject
#include "refs.i"
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- OPTIONS
-
- EXAMPLES
-
- RESTRICTIONS
-
- SEE ALSO
-
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