gmt begin GMT_earthmask
gmt makecpt -Clightblue,burlywood,blue,red,white -T-0.5/4.5/1 -N
gmt grdimage @earth_mask_05m -JQ0/15c -Baf -BWsNe
gmt legend -DJBC+w15c+o0/0.5c -F+p1p << EOF
N 5
S - s 0.5c lightblue 0.25p - Ocean [0]
S - s 0.5c burlywood 0.25p - Land [1]
S - s 0.5c blue 0.25p - Lake [2]
S - s 0.5c red 0.25p - Island [3]
S - s 0.5c white 0.25p - Pond [4]
EOF
gmt end show