I have a map using an oblique region, defined by -R-104.98/-4.549/-104.82/-4.548+r with projection -JOA-104.9/-4.56/100.5/7i and a line that goes off the map. Is it possible to find the intersection between the (west) edge of the map and this line? I essentially need to be able to extract the coordinates of the lower left and upper left corners of the map and then use gmt spatial line.txt westborder.txt -Ie, but I have not figured out how to get the upper left corner. The closest I have been able to get is gmt mapproject -R$region -J$Jparam -Wr, but that doesn’t actually give the region I desire (not the bounding meridians), not to mention that it gives the meridians in 0-360 units and not -180-180…
What about mapproject -WE?
That just returns my original region (but in 0-360 format):
-R255.0200000000099/-4.54900000000183/255.180000000001/-4.548000000000185+r
Interestingly, it appears that this introduces a very small but of numerical error.
mapproject -We+n2
should return a closed rectangle with all 4 corner coordinates. choose your corner.