Understanding visibility analysis

The shape of a terrain surface dramatically affects which parts of the surface someone standing at a given point can see. What is visible from a location is an important element in determining the value of real estate, the location of telecommunications towers, or the placement of military forces. ArcGIS 3D Analyst allows you to determine visibility on a surface from point to point along a given line of sight or across the entire surface in a viewshed.

What is a line of sight?

A line of sight is a line between two points that shows the parts of the surface along the line that are visible to or hidden from an observer. Creating a line of sight allows you to determine whether a given point is visible from another point. If the terrain hides the target point, you can see where the obstruction is and what else is visible or hidden along the line of sight. The visible segments are shown in green, and the hidden segments are shown in red. A black dot at the beginning of the line represents the observer location. A blue dot represents the point of obstruction from the observer to the target. A red dot at the end of the line represents the target location.

To create a line of sight interactively, set the offset of the observer and target points above the surface, then click the observer and target points - a graphic line representing the line of sight appears between them. The line of sight is shown in the scene above as a green and red 3D line graphic that follows the surface. Although you cannot create a line of sight in ArcScene, you can create one in ArcMap and copy and paste it into a scene.