I am plotting geopotential height data with geoshow and would like to have coastlines superimposed on my data. In the code below, data is a 41x25 matrix. The shape of the matrix is always the same, but the values change with different levels of geopotential height. For my first level, the code below works as desired (first attached image). However, when I change the levels, the coast lines appear incomplete (second image) or not at all (third image). I do not change the code that produces the image, only the values in data change, as reflected by the scale on the colourbar. Any suggestions about where the problem is here would be greatly appreciated.
fig1= figure ('name', 'test');
geoshow(latgrid, longrid, data, 'DisplayType','surface')
coast = load('coast.mat');
c = colorbar;