In the Add Rasters To Mosaic Dataset tool, the default Raster Type is Raster Dataset. However, if the input data is a terrain dataset, the Raster Type field must be set to Terrain, otherwise the tool cannot add terrain datasets to a mosaic dataset.
When this value is set in the Raster Type field, a warning is displayed next to the Raster Type field: "000159: Raster type could not be validated. Please open the raster type properties page and specify the cell size." This means the user must define a cell size for the terrain, just as a standard non-terrain raster would have a cell size associated with the raster data format.
If the terrain is created from a point feature class, a possible starting value for the terrain cell size is the average point spacing value obtained from the Point File Information geoprocessing tool (3D Analyst Conversion Toolbox > Conversion > From File). The point spacing is most accurate when the rectangular extent of the file being examined is filled with data. Files with points over large water bodies or on the perimeter of a study area, only partially occupied with data, will not produce accurate estimates. The instructions below describe how to add a terrain dataset in the Add Rasters to Mosaic Dataset tool.
Adding a terrain dataset
1. In the Raster Type field, select Terrain as the data type.
2. Click the Properties button at the right of the field to open the Raster Type Properties dialog box.
3. On the Terrain page, set the pixel size in the units of the terrain dataset coordinate system.
For more information about the settings, click the About the Terrain raster type property link.
The pixel size must be set based on the density and accuracy of the terrain data, as well as the system's processing capabilities. The terrain's pixel size can be changed to be smaller or larger than the average point spacing, and the pixel value will be interpolated from the terrain data.