# Surimposed geophysical fields and topography **URL:** \ **Category:** Q&A\ **Created:** [April 21, 2020, 6:07am UTC](https://forum.generic-mapping-tools.org/t/surimposed-geophysical-fields-and-topography/401 "2020-04-21T06:07:36Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![wbm06](https://avatars.discourse-cdn.com/v4/letter/w/34f0e0/32.png) [@wbm06](https://forum.generic-mapping-tools.org/u/wbm06)\ **Post date:** [April 21, 2020, 6:07am UTC](https://forum.generic-mapping-tools.org/t/surimposed-geophysical-fields-and-topography/401/1 "2020-04-21T06:07:36Z")
Dear all, I am using GMT5 and I am trying to get on the same figure LAB depth and surface topography. But I did not understand what I misunderstood or miss to get this figure. Any comments or suggestions. Cheers /bin/rm tmp.ps tmp.cpt gmt makecpt -Crainbow -T40/300/50 -Z \>tmp.cpt #### Make a basemap of central and southern Africa: gmt psbasemap -R-1.5/50.5/-35.5/11.5 -JM14 -Ba2f1 -P -X2.0 -Y15 -K \>tmp.ps #### Convert the xyz file into GRD file using xyz2grd awk ‘{print $1, $2, $3}’ LAB.xyz | gmt xyz2grd -R -I0.5 -Gtmp.grd #gmt grdimage tmp.grd -JM -Ctmp.cpt -E50 -K -O \>\>tmp.ps #### Resample tmp.grd from coarse (0.5 deg.) into finer resolution (0.1 degree) using grdsample. # The output file is tmph.grd. gmt grdsample tmp.grd -Gtmph.grd -I0.1 ### Cut out the portion of elevation data from a global database #### The output is topo0.grd gmt grdcut etopo1\_bedrock\_africa.grd -Gtopo0.grd -R ### Resample it into the same interval as tmph.grd grdsample topo0.grd -Gtopoh.grd -I0.1 #### Produce the gradient file. This time I usd -Nt to make a more dramatic shade gmt grdgradient topoh.grd -Gtopoh.int -A45 -Nt #### Produce the image using the resampled grd file and tmp.int gmt grdimage tmph.grd -Itopoh.int -Ctmp.cpt -R -J -O -K \>\>tmp.ps #### Overlay with coastlines and political boudnaries gmt pscoast -R -JM -B2f2 -A1000 -W1 -N1 -D -P -V -K -O \>\> tmp.ps #### Plot the scale bar at the bottom of the plot gmt psscale -Ctmp.cpt -Dx8c/1c+w6c/0.5c+jTC+h -Bxaf+l"LAB " -By+lkm -K -O -Y-2.5 \>\> tmp.ps ---
**Author:** ![Joaquim](https://yyz1.discourse-cdn.com/flex047/user_avatar/forum.generic-mapping-tools.org/joaquim/32/16_2.png) [@Joaquim](https://forum.generic-mapping-tools.org/u/Joaquim)\ **Post date:** [April 21, 2020, 10:51pm UTC](https://forum.generic-mapping-tools.org/t/surimposed-geophysical-fields-and-topography/401/2 "2020-04-21T22:51:48Z")
Sorry, but is the question exactly? ---
**Author:** ![wbm06](https://avatars.discourse-cdn.com/v4/letter/w/34f0e0/32.png) [@wbm06](https://forum.generic-mapping-tools.org/u/wbm06)\ **Post date:** [April 21, 2020, 11:49pm UTC](https://forum.generic-mapping-tools.org/t/surimposed-geophysical-fields-and-topography/401/3 "2020-04-21T23:49:47Z")
Sorry, my question is how can we get topography in background and LAB depth or Moho depth on the top. The script I put here doesn’t work and I dont know why. ---
**Author:** ![Esteban82](https://yyz1.discourse-cdn.com/flex047/user_avatar/forum.generic-mapping-tools.org/esteban82/32/54_2.png) [@Esteban82](https://forum.generic-mapping-tools.org/u/Esteban82)\ **Post date:** [April 21, 2020, 11:54pm UTC](https://forum.generic-mapping-tools.org/t/surimposed-geophysical-fields-and-topography/401/4 "2020-04-21T23:54:04Z")
Maybe you could add transparency (-t50) to the top grid. ---
**Author:** ![wbm06](https://avatars.discourse-cdn.com/v4/letter/w/34f0e0/32.png) [@wbm06](https://forum.generic-mapping-tools.org/u/wbm06)\ **Post date:** [April 22, 2020, 12:46am UTC](https://forum.generic-mapping-tools.org/t/surimposed-geophysical-fields-and-topography/401/5 "2020-04-22T00:46:20Z")
> [@Esteban82](#): > > -t50 which line of the script? ---
**Author:** ![Esteban82](https://yyz1.discourse-cdn.com/flex047/user_avatar/forum.generic-mapping-tools.org/esteban82/32/54_2.png) [@Esteban82](https://forum.generic-mapping-tools.org/u/Esteban82)\ **Post date:** [April 22, 2020, 12:49am UTC](https://forum.generic-mapping-tools.org/t/surimposed-geophysical-fields-and-topography/401/6 "2020-04-22T00:49:49Z")
> [@wbm06](#): > > gmt grdimage tmph.grd -Itopoh.int -Ctmp.cpt -R -J -O -K \>\>tmp.ps In this line of the script. ---
**Author:** ![wbm06](https://avatars.discourse-cdn.com/v4/letter/w/34f0e0/32.png) [@wbm06](https://forum.generic-mapping-tools.org/u/wbm06)\ **Post date:** [April 22, 2020, 1:24am UTC](https://forum.generic-mapping-tools.org/t/surimposed-geophysical-fields-and-topography/401/7 "2020-04-22T01:24:03Z")
> [@Esteban82](#): > > gmt grdimage tmph.grd -Itopoh.int -Ctmp.cpt -R -J -O -K \>\>tmp.ps Thanks Esteban82. It seems that I have another problem. For mysterious reasons tmph.grd and topoh.grd are not the same size. 🤔