Upward openness maps show ridge crests in white, while downward openness maps show valleys in white. They provide dramatic depictions of terrain.

Reflectance |
Upward (Positive) openness |
Downward (Negative) openness |

Choice of upward (positive) and downward (negative) openness. For each select a region size in meters, because openness is defined as a maximum or minimum angle over a specified region. The region size should be at least as large as the ridge/valley spacing in the region. The Graph parameter by Region size option can help you pick the value by seeing the inflection points.

Openness calculates an angle in each of 8 radials in the
principal compass directions. The diagrams to the left shows two of the
angles computed for upward openness. The peak in the top diagram will have
a high value for openness, while the valley in the bottom diagram will
have a small value. The Value L shows the distance used for the computation; for the peak, visibility extends all the way out to L, while for for valley, the steep walls block visibility well before the L distance. If you want, you can only use some of the 8
radial directions. This is set on the |

Openness maps correlate strongly with maximum and minimum curvature.

Short distance openness maps can be very effective with urban lidar DSM.

Last revision 11/26/2017