Area Target Properties

Area Target Boundary

This page lets you define and edit the boundary points that make up the perimeter of an area target and also view the area covered by the area target. The maximum number of boundary points that can be edited for an area target is set on the General Preferences properties page. For area targets with more boundary points than the maximum, the Boundary properties page for the Area Target is disabled and the area covered by the area target must be computed manually by clicking Compute. (Keep in mind that the computation cannot be stopped or interrupted once you start it.)

A self-intersecting area target cannot be filled and its area cannot be computed.

Begin by setting the Area Type to pattern or ellipse.

You can also define the entire area target boundary by clicking in the 2D Graphics window. If you use the mouse in the 2D Graphics window to define the area boundary, be sure that the Basic Boundary page is open. You do not need to click OK or Apply after you have defined the area boundary in the 2D Graphics window. You will need to click OK or Apply if you have made any other changes on the Boundary properties page.

The Area field displays the area of the currently defined target in the selected unit.

For more information on setting object properties using the mouse, see Mouse Shortcuts

Pattern Area Type

Specify the position of perimeter points by entering the appropriate values in the table or by clicking in the 2D Graphics window at the location of each point.

If you do not specify a boundary with at least three points, the area target is not defined.

The Points table displays a summary of the latitude and longitude values for each perimeter point. You can add, change, or delete points as follows.

Add Perimeter Points

1. Click Add beside the Points table to add a line of data representing a boundary point.
2. Edit the Latitude and Longitude values for each point by double-clicking the appropriate field in the table and entering the desired value in the editable field.
3. Repeat steps 1 and 2 to define each point along the boundary of the area target.
4. Click OK or Apply to save your changes.

After you enter the first boundary point, you can turn on the Add New Point option in the Map Pick Mode area, and click anywhere in the 2D Graphics window to add additional boundary points (latitude/longitude values) to the table.

Edit Perimeter Points

1. Double-click the latitude or longitude value in the line of data representing the boundary point that you want to change.
2. Enter the new latitude or longitude values.
3. Click OK or Apply to save your changes.

After you enter the first boundary point, you can turn ON the Change Selected Point option in the Map Pick Mode area, and click anywhere in the 2D Graphics window to change boundary points (latitude/longitude values).

Delete Perimeter Points

1. Select the line of data representing the boundary point that you want to remove.
2. Click Remove.
3. Click OK or Apply to save your changes.

Items in the Points list can be removed individually or as a group. If you want all points along the boundary of an area target to be removed, use the Remove All button.

Ellipse Area Type

Define an elliptical area boundary using the following parameters:

Option	Description
Semimajor Axis	Half the length of the ellipse's long axis.
Semiminor Axis	Half the length of the ellipse's short axis.
Bearing	The angle, measured in an easterly direction, between the major axis of the ellipse and the local North direction.

The axes of the ellipse are measured on the surface of a theoretical sphere with a radius the same as the radius of the central body at the center of the area target: