unix - Mercator projection with metric grid overlay (metre increments from centre) - GMT Generic Mapping Tools -

i have plot of montserrat, centred on -62.2°,16.75°, mercator projection created using generic mapping tools (gmt), below.

i add grid on top of this, using centre origin. however, produce overlying grid in terms of metres, rather degrees. there way in can assign -62.2°,16.75° origin, , produce grid lines of multiples of 1000m origin (1000m, 2000m, 5000m, etc) (perhaps through psxy?)?

the code used produce 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 degrees meters; grid super small

gmt pscoast -r-62.25/-62.12/16.65/16.84 -jm6i -p -b.01666666g.00898311174 -ggray -dh -slightblue -wred > gmt_tut_4.ps