How to avoid the funky look of -JT and -SE-?

Q&A
1

I was surprised by the funky look of the Transverse Mercator projection (-JT) when combined with some -SE- on the plot borders (tuned for extra visual appeal):

tissot11
tissot11487×647 148 KB

Those Tissot’s Indicatrix are not supposed to look that spiky. Is this some clipping at the borders going rogue?

gmt begin tissotJT pdf
  gmt coast -R0/360/-80/80 -JT-15/15/15c -Bpg30 -Bsg90 -Ba30 -B+t" Transverse Mercator projection (-Jt -JT)" -Wthinnest,gray -Glightgray
  gmt plot indicatrix.txt -SE- -Gred@50 -Wred
gmt end show

indicatrix.txt (826 Bytes)

2

No way to avoid that bug except to say clear of the periodic boundary in the y-direction. I have added a small version of this as a failing test script to our test suite, see https://github.com/GenericMappingTools/gmt/pull/4681

3

The bug has been identified and fixed in a PR being considered for approval. WIth the fix your plot looks like this instead:

tissotJT
tissotJT1947×2578 403 KB

4

Thank you @pwessel, now works like a charm!