How can I put my curvilinear coordinate data in a map projection?
The map projection scripts assume that the I,J indices from a dataset are associated with longitude and latitude respectively. This assumption allows the scripts to define the following variables which are used by all the map projections:
let/quiet Pi = 3.14159265 let/quiet deg2rad = Pi / 180.0 let/quiet mp_x = x let/quiet mp_y = y let/quiet mp_lambda = mp_x * deg2rad let/quiet mp_phi = mp_y * deg2radWhen you have curvilinear data this assumption no longer holds and you must alter the definitions of
mp_lambda
and mp_phi
to use longitude and
latitude matrices which describe the locations of your data. In the script below,
this is accomplished with:
let mp_lambda = my_lon[d=arctic.lon] * deg2rad let mp_phi = my_lat[d=arctic.lat] * deg2rad
The journal file to create this plot is:
! Set the region and define the map projection. ! Plot the underlay. ! Add a graticule. ! set win/size=.3/asp=1:ax set region/x=270:630/y=-90:90 go mp_orthographic 90 60 use coads_climatology set grid sst shade/noaxis/nokey/title="Sea Ice Concentration (percent coverage) and SST" sst[t="15-mar"]*mp_mask, x_page, y_page go mp_graticule ! Read in the data defined on the curvilinear axes. ! define axis/x=1:80:1 iindex define axis/y=1:58:1 jindex define grid/x=iindex/y=jindex coord_grid file/var=my_lon/columns=80/grid=coord_grid arctic.lon file/var=my_lat/columns=80/grid=coord_grid arctic.lat file/var=ice/columns=80/grid=coord_grid aricecon.dat set variable/bad=-1 ice ! Redefine the mp_~ variables for the curvilinear data ! let mp_lambda = my_lon[d=arctic.lon] * deg2rad let mp_phi = my_lat[d=arctic.lat] * deg2rad ! We need to cancel the region because the i,j indices ! on the curvilinear grid have do not have the same meaning ! as the i,j indices from the COADS dataset. ! set grid ice can region shade/over/key/nolabel/noaxis/pal=grayscale ice*10, x_page, y_page ! Restore the mp_~ variables to their original settings ! let mp_lambda = mp_x * deg2rad let mp_phi = mp_y * deg2rad set region/y=-90:90 go mp_fland 60
Last modified: Jun 29. 1999