function []=fld_plot(tl,rkm,zr,dbmin,dbmax,case_name)
% Plot the acoustic transmission loss field versus range and depth
% using the pseudo color plot pcolor and a gray scale determined by
% dbmin and dbmax.
figure;
pcl=pcolor(rkm,zr,tl);
hold on;
caxis([dbmin dbmax]);
shading flat;
color_levels=32;
colormap(gray(color_levels));
set(gca,'ydir','reverse');
title(case_name);
xlabel('Range (km)');
ylabel('Depth (m)');
colorbar;