O.3.4 Label placement at simple line intersections

Often, it will suffice to place contours at the imaginary intersections between the contour lines and a well-placed straight line segment. The -Gl or -GL algorithms work well in those cases:

pscoast -R50/160/-15/15 -JM5.5i -Glightgray -A500 -K -P > GMT_App_O_4.ps
grdcontour geoid.grd -J -O -B20f10WSne -C10 -A20+d+s8 -GLZ-/Z+ -S10 -T:LH >> GMT_App_O_4.ps

The obvious choice in this example is to specify a great circle between the high and the low, thus placing all labels between these extrema.

Figure O.4: Labels are placed at the intersections between contours and the great circle specified in the -GL option.

The thin debug line in Figure O.4 shows the great circle and the intersections where labels are plotted. Note that any number of such lines could be specified; here we are content with just one.