GRDPROJECT

Section: Misc. Reference Manual Pages (l)
Updated: DATE
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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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Time: 07:11:54 GMT, January 07, 2025