I am having similar issue as (https://groups.google.com/forum/#!topic/cesium-dev/GimzfxR4Guo). I have attached the snapshot of the result that I am getting with 10m resolution DEM (Cartodem-10m). Initially it was Float-32 type(for which I used bil-32 from geoserver), but even after converting to Int-16 type (and using bil-16 from geoserver) same issue is recurring. I am using Cesium-1.13 and Geoserver 2.8.0. Any solutions?