Constraining area of hillshading from DEM/TIN

Discussion created by mud on Jun 17, 2014
Latest reply on Jun 18, 2014 by mud

I have made hillshading from contour data of an island I am working on but I cannot ???remove??? the grey fill area with a Pixel Value of 180 that fills in the sea. I tried Layer Properties ??? Symbology ??? Display Background Value ???180??? as ???white???, which I have used in other places to remove backgrounds, but of course this made all areas with a value of ???180??? go white, destroying the hillshading, so it is obviously the wrong approach.

To make the hillshading, I first made a TIN of the contour data, then a DEM from the TIN. I removed the background value in the DEM by the method described above (set background to white) and then made hillshading from the DEM. However, I can see that the TIN fills in the sea area in bays with triangles (TINs) and I wonder if it is these that are causing my problem.

I suspect I need to either restrict the formation of the TIN or the formation of the hillshading to within my coastline. I tried various options but none that I tried worked.

Any suggestions?

If this is not the cause of the problem, any other suggestions would be welcome.