There is a color scale and a numerical scale of the data. The numerical values are mapped to the color values. You can choose between several predefined color palettes by right-clicking on the color palette toolbar.

Also there are several mapping modes. The simplest is “Autoscaling” - in this mode the color map is stretched from minimum to maximum of the data. Also you can select an area on the image and set is as a “Region of interest” - then the minimum and maximum will be taken from this area.

Another common mode is “Fixed” - in this mode you can manually select the range and offset of the color map. If you double-click the color palette toolbar, the limits will be set to the maximum and minimum of the data - this is a good point to start from.

The numerical Z scale of the surface image can be shown in different ways - in absolute or in relative coordinates, in different units. This parameters can be selected in “Preferences” dialog (appears after a right-click on the image)