%D = integer degrees %<width.precision>d = floating point degrees %M = integer minutes %<width.precision>m = floating point minutes %S = integer seconds %<width.precision>s = floating point seconds %E = label with E/W instead of +/- %N = label with N/S instead of +/-For example, the command set format x "%Ddeg %5.2mmin %E" will cause x coordinate -1.51 to be labeled as " 1deg 30.60min W".
If the xtics are left in the default state (set xtics numeric) the coordinate
will be reported as a decimal number of degrees, and format will be assumed
to contain normal numeric format specifiers rather than the special set above.