I have a plot of Montserrat, centred on -62.2°,16.75°, with a Mercator projection created using Generic Mapping Tools (GMT), as below.
I would like to add a grid on top of this, using the centre as the origin. However, I would like to produce the overlying grid in terms of metres, rather than degrees. Is there a way in which I can assign -62.2°,16.75° as the origin, and then produce grid lines of multiples of 1000m from the origin (1000m, 2000m, 5000m, etc) (perhaps through psxy?)?
The code used to produce this plot is
set loc_area = -R-63.2/-61.2/15.75/17.75
set loc_proj = -Jm3.25i
set outfile = bath_map.ps
psbasemap $loc_area $loc_proj -O -Bf1a1WSen:.'Montserrat Local': -X7.5i -Y0 -K >> $outfile
grdimage $loc_area $loc_proj -O -Clant.cpt lant_topo.nc -K >> $outfile
grdcontour lant_topo.nc -Ccont.cpt -A- -Q100 -W $loc_area $loc_proj -O -K >> $outfile
Just convert the degrees into meters; your grid will be super small