I'm trying to do something really simple, plot a rectangle using psxy on a .cdf grid file. Something like:
grdimage grid.cdf -JM20c -R-70/0/20/60 -Bf20g10 -K > image.ps psxy rectangle.dat -JM -R -B -W0.5p -O >> image.ps
My rectanle.dat file is a two column file with 5 lon/lat points. Once plotted, the rectangle has two straight vertical sides and two curved upwards horizontal sides and I cannot figure out why. Any ideas?