Could you help me please.
The first question
In the format description http://cesiumjs.org/data-and-assets/terrain/formats/heightmap-1.0.html says that the size of the height map is 65 * 65.
If the tile has a mix of land and water, it is necessary to fill the additional mask with size of 256 * 256.
I do not understand which the size of the tile: 65*65 or 256*256.
I have two choices:
1) tile size is 256 * 256, and a height map is constructed by decimation;
2) tile size is 65 * 65, and the mask is constructed by interpolating.
The second question
How to distinguish between land and water?
Do I understand correctly that if the pixel value on the tile is less or equal to zero, this point corresponds to the water, otherwise it corresponds to the land?