Thanks. So if I use psvelo and try this example:
gmt psvelo data_test -R -JM -Sn0.2i -W2p,red with data_test format
Longitude Latitude phi dt which is the output format from this kind of analysis) it cannot work.
if I use
gmt psxy data_test -R -JM -Sv0.2i -W2p,red, I am almost there but I want to have the bar centred and not started from Long, Lat
Any comment or advice to get a correct figure with anisotropy bars in the correct azimuth and length from the input file?