How to plot sphdistance

Q&A
1

Good afternoon all, Please can someone help me out on how to plot sphdistance, I have be trying it for the past 4 days but not able to plot it. I need help on it, below is the code, table and the plot for your assistance

gmt begin map pdf

 gmt set MAP_FRAME_TYPE plain
 gmt set FONT_LABEL 16p
 gmt makecpt -Cjet -T-15/30/2
gmt pscoast -R16/33/-35/-22 -JM20c -BWSne -Baf -I1/1p,0/200/251 -W1,black -Gwhite -Di -N2/0.25p,black -Na/0.5,black  -Swhite > SA.ps 
 gmt sphtriangulate sphdist.dat -Qv -D > t.txt
 gmt sphdistance -R16/33/-35/-22 -I1 -Q -Gsphdistance.nc -Lk
 gmt grdcontour sphdistance.nc -JM20c -C200 -A1000 -Bafg

gmt end show

##long lat Baselin distance trend (mm/yr) strain rate (ns/yr)
28.73 -25.8 brnk-kman 585482.7849 0.529872 0.905017216
28.73 -25.8 brnk-krug 101591.861 0.807424 7.947723293
28.73 -25.8 brnk-kstd 253915.681 -0.42579 -1.676895252
26.51 -33.32 grhm-grnt 219699.4559 -0.963341603 -4.384815607
26.51 -33.32 grhm-heid 775992.9562 -1.164514529 -1.500676674
26.51 -33.32 grhm-hrac 831168.1609 -0.131461888 -0.158165211
26.51 -33.32 grhm-ixop 487358.5262 -0.009527236 -0.01954872
26.51 -33.32 grhm-kley 532649.8163 -0.087179301 -0.163670949
26.51 -33.32 grhm-kman 760152.5533 -0.413122831 -0.543473583
26.51 -33.32 grhm-krug 811154.678 -0.748993613 -0.923367187
26.51 -33.32 grhm-kstd 630845.0232 0.416425222 0.66010701
24.53 -32.25 grnt-heid 736888.7823 -2.013026227 -2.731791114
24.53 -32.25 grnt-hrac 768219.0729 -0.977451076 -1.272359813
24.53 -32.25 grnt-ixop 576341.3867 -1.151929874 -1.998693657
24.53 -32.25 grnt-kley 389345.7837 -0.397910006 -1.021996442
24.53 -32.25 grnt-kman 513058.4321 -0.328268625 -0.639826977
24.53 -32.25 grnt-krug 751818.3475 -1.404661767 -1.868352603
24.53 -32.25 grnt-kstd 571143.9313 -0.117879776 -0.206392416

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2

Your data are duplicative. Their are sets of 3 identical points all over

sphtriangulate [ERROR]: STRIPACK: Failure in TRMESH. The first 3 nodes are collinear.

3

Looks like you only have 3 unique points

4

I have more than that but only wanted to try with those point first, then if i get right I can then plot the points. Is the table right please, don’t really know how to set the table for sphdistance.

5

Please sir can I get sample on how the table to plot the sphdistance look like.
Thanks for your assistance

6

As for almost all gmt table reader modules, it expects lon, lat [, z] so your table is readable but all those repeated coordinates will keep giving you errors since one cannot make triangles out of 3 copied points.

Also, surely you have already looked at example 35 in the illustration gallery which shows sphdistance input and output? The purpose of the documentation is to actually use it.