## Description

The input raster is missing the vertical coordinate system.

## Solution

The vertical coordinate system of the input raster is used internally to compute the z-factor and the height of the target locations. Assign a vertical coordinate system for the input raster if it does not have one.

To add a vertical coordinate system, use the Define Projection tool. In the first parameter, specify the raster dataset as the input dataset. In the second parameter, click the Properties button. The Spatial Reference Properties dialog box appears. Click the Z Coordinate System tab on the dialog box and choose the z-coordinate system.

If the vertical coordinate system of the input raster is left undefined, the tool will run, but the z-unit of the input raster is assumed to be the same as its x,y-unit.