+v misses the point

Q&A
1

Dear Gurus,

when adding arrowheads to a multisegment line the arrowheads don’t point on the coordinate of the origin/termination of the multisegment line at least when using -JG. No difference between -v/-vb/-ve. A single line is no problem.

cat > path.txt << END
 30.3  51.5
  8.2  70.4
-71.8  61.2
END

gmt begin earth_arrowhead
  gmt basemap -Rg -JG8.1703/49.9816/15c -Bg
  gmt plot path.txt -W2p,green
  gmt plot path.txt -W1p,red+v0.5c
  gmt plot path.txt -Skcrosshair/0.5c -Wthinnest,black
gmt end show

earth_arrowhead
earth_arrowhead1777×1777 625 KB

I expected the red line to run the same track as the green line with both arrows pointing into the respective crosshair symbols. Am I missing something?

2

I’m still not sure what is going on here. After some more experimentation I found, that single segment lines are fine and only multi segment lines show this strange behavior.

Maybe one of the Gurus can explain what’s going on here?

earth_arrowhead
earth_arrowhead1777×1777 429 KB

cat > path.txt << END
>
 45  45
  0  75
-75  60
>
 45  30
-75  45
>
 30  30
-30  15
>
 45  15
 0  -15
-75  30
END

gmt begin earth_arrowhead
  gmt basemap -Rg -JG8/50/15c -Bg
  gmt plot path.txt -W2p,green
  gmt plot path.txt -W1p,red+v0.5c
  gmt plot path.txt -Skcrosshair/0.5c -Wthinnest,black
gmt end show