multiple grdimage ovelay

13 Apr 2019

Question

if you have more than one grd data to plot at one figure, you may need know this trick.
there are three steps:

1. gridding your data
2. set 0 or other special value to NAN
3. force NAN to be transparent

code

# first step 
gmt xyz2grd $TXT $RR -I0.022d/0.02d  -G$GRD
# second step, the key is +n0, which make 0 to be flaged as NaN
gmt grdconvert $GRD2 -Gtmp.grd=nb+n0
# third step, -Q force NAN to be transparent
gmt grdimage $JJ $RR tmp.grd  -C$CPT2 -Q -K -O >>$P

example

plot two edges on one figure.