Generate the contour plot. LEVELS= specifies the values of the contour levels. LLEVELS= sets the line types for the contour lines. Solid lines identify negative contour levels, and dashed lines identify positive contour levels. 
proc gcontour data=reflib.pondgrid;
   plot vdist*hdist=height /levels= -30 -12 -7  -3 0 3 5 7 12
                            llevels=  1   1  1  1  1 2 2 2 2  2
                            legend=legend1
                            haxis=axis1
                            vaxis=axis2;
run;
quit;