Hillshade function
A hillshade is a grayscale 3D model of the surface, with the sun's relative position taken into account for shading the image. This function uses the latitude and azimuth properties to specify the sun's position.
The inputs for this function are the following:
- Input DEM
- Azimuth
- Altitude
- Z Factor
By default, a grayscale color ramp is used to display a hillshaded elevation model. The following image displays an elevation model using the default hillshade symbology.
Azimuth and Altitude
The properties altitude and azimuth together indicate the sun's relative position that will be used for creating any 3D model (hillshade or shaded relief). Altitude is the sun's angle of elevation above the horizon and ranges from 0 to 90 degrees. A value of 0 degrees indicates that the sun is on the horizonâ€”that is, on the same horizontal plane as the frame of reference. A value of 90 degrees indicates that the sun is directly overhead.
Azimuth is the sun's relative position along the horizon (in degrees). This position is indicated by the angle of the sun measured clockwise from due north. An azimuth of 0 degrees indicates north, east is 90 degrees, south is 180 degrees, and west is 270 degrees.
Z Factor
The scaling factor used to convert the elevation values. The scaling factor is used for two purposes: first, to convert the elevation units (such as meters or feet) to the horizontal coordinate units of the dataset, which may be feet, meters, or degrees, and second, to add vertical exaggeration for visual effect.
To convert from feet to meters or vice versa, see the table below. For example, if your DEM's elevation units are feet and your mosaic dataset's units are meters, you would use a value of 0.3048 to convert your elevation units from feet to meters (1 foot = 0.3048 meters).
This is also useful when you have geographic data (such as DTED in GCS_WGS 84 using latitude and longitude coordinates) where the elevation units are in meters. In this case, you need to convert from meters to degrees (0.00001; see below). The value for degree conversions are approximations.
From | To | ||
---|---|---|---|
Feet | Meters | Degrees | |
Feet | 1 | 0.3048 | 0.000003 |
Meters | 3.28084 | 1 | 0.00001 |
To apply vertical exaggeration, you must multiply the conversion factor by the exaggeration factor. For example, if both elevation and dataset coordinates are meters and you want to exaggerate by a multiple of 10, the scaling factor would be unit conversion factor (1.0 from the table) multiplied by the vertical exaggeration factor (10.0), or 10. As another example, if the elevations are meters and the dataset is geographic (degrees), you would multiply the units conversion factor (0.00001) by 10 to get 0.0001.