Is this the case only for mapproject?
If I run
gmt pscoast -Jstere/0/90/1:10000000 -Bafg -W -RNO -pdf stereotest
is it gmt or proj that does the projection calculation?
Fun: I once wanted to test; gmt vs. proj: is the projection identical?
ps=proj_vs_gmt.ps
#dump coast line and proj to mercator, replace # with >
gmt psxy --PS_MEDIA=A0 \
<(sed "s/#/>/g" <(proj +proj=merc +lon_0=0 +ellps=WGS84 <(sed "s/>/#/g" <(gmt pscoast -ENO -M)))) \
-R0/3460000/7920000/11410000 -P -JX20c -Wthick,black -K > $ps
#project norge.gmt to mercator with GMT
gmt pscoast -ENO -M | gmt mapproject -Jm0/1:100 -R4/32/57/72 -C | \
gmt psxy -R -J -Bafg -BWeSn+t"proj vs. gmt" -O -Wred >> $ps
gmt psconvert -Tg -A -Z $ps
rm gmt.history
Making gmt use proj4 would be a huge deal in my opinion. proj-stuff is everywhere.