Geographic Basemap - Axes Annotation Orientation

I am creating a map using the Oblique Mercator projection. The labelling of the axes looks like this:


I want to rotate the Longitude annotations by 180°, so that they are more readable. Is that possible? I’ve looked at -B+a, but that doesn’t work for geographic basemaps. I’ve also looked at MAP_ANNOT_ORTHO, but that has no effect either.

Can you send the psbasemap command that makes the frame please? See MAP_ANNOT_OBLIQUE for various options.

Basemap command is:

psbasemap -Ba10g5 -JOA133.1/-2.7/143.95/500 -Rn-2600/2600/-800/800 -O -K >> %ps%

Thanks, looks like GMT4 syntax to me. Anyway, something like this

gmt psbasemap -Ba10g5 -JOA133.1/-2.7/143.95/9i -R-2600/2600/-800/800+un --FORMAT_GEO_MAP=dddF --MAP_ANNOT_OBLIQUE=0 >

avoids the overprinting. There should never be a need to rotate by 180 unless you are also rotating the figure after it is made. All the annotations above are readable and not backward.

Thanks for that Paul. You have actually revealed the underlying problem and that is I am rotating the figure 90° after it is made. The oblique equator is parallel to the x- axis and I want it to be parallel to the y-axis, hence the 90° rotation. I’ve asked the question about that in a separate post.
Thanks for the prompt reply.