Options | Point Entry | Save

Sensor Pattern Tool

The Pattern tool is available to all sensors attached to vehicles. The sensor pattern is defined by a set of directions specified by azimuth and elevation. Use the Pattern Tool to create a custom sensor pattern or to edit an existing sensor pattern by defining the perimeter points that mark the boundaries of the sensor pattern.

The azimuth and elevation values may be entered manually or are computed from points on the ground (specified manually or loaded from an AreaTarget). When computing to points on the ground, the direction to each point is computed from the parent's vehicle location at the specified input time (ignoring any blockage by the central body itself). That direction is represented using azimuth and elevation measured with respect to the parent vehicle's body axes (not the sensor's body axes) at that input time.

Once computed using the parent vehicle's body axes, the azimuth and elevation values are treated as standard Custom sensor pattern data in Az-El mask format, with azimuth and elevation being interpreted as defining direction in the sensor's body frame (not the parent vehicle's body frame). It is typical when defining a custom sensor pattern using points on the ground to choose the sensor's pointing to align the sensor body axes with its parent vehicle's body axes so that the projection of the sensor aligns with the input points on the ground at the input time.

To create a custom sensor pattern using the Pattern Tool, follow these steps:

  1. Select the Custom Sensor Type on the sensor's Definition properties page.
  2. Click Pattern Tool.
  3. Specify the time that the sensor should use when calculating the parameters that make up the sensor pattern.
  4. Choose a point type.
  5. Create perimeter points that define the sensor pattern.
  6. Choose whether or not to display the sensor's boresight.
  7. Choose whether or not to display the field of regard.
  8. Choose whether or not to have STK interpolate between data points.

Pattern Tool Options

OptionDescription
TimeSpecify the time that the sensor should use when calculating the parameters that make up the sensor pattern. Typically this time coincides with the passage of the vehicle over a particular point on the Earth.
Point TypeThe Point Type determines the way in which you specify the perimeter points.
Show BoresightIf enabled, a boxed X representing the boresight graphically displays in the 2D Graphics window. Show Boresight is enabled by default.
Show Field of RegardIf you select this check box, STK outlines the horizon of the sensor in the 2D Graphics window. Show Field of Regard is enabled by default.
Do not interpolate between pointsSelect this option to disable interpolation, i.e., STK will not add interpolated points between the input points in the table. If not selected, STK will add more points when the existing points are greater than a user-specified angular distance apart.

Using this option (preventing interpolation) may cause inaccuracies in access or problems trying to visualize the custom sensor in 2D or 3D Graphics if your points are greatly spaced.

Point types

You can choose from the following Point Types to specify the perimeter points that define the boundaries of a custom sensor.

Point TypeDescription
Latitude, LongitudeSpecify individual earth latitude and longitude pairs in the points list to create a ground perimeter projection of the sensor pattern.
Azimuth, ElevationSpecify individual azimuth and elevation pairs in the points list. Azimuth is measured in the XY plane of the sensor about its boresight (Z axis). It is right-handed for space-based sensors and left-handed for ground-based sensors. Elevation is defined as the angle above the XY plane of the sensor, with its boresight being 90 degrees.
Enter from Area TargetUse the latitude and longitude pairs that define an area target's perimeter. If you choose this option, specify the Area Target File Name or click Load... to browse for a file. After you enter a valid file name, the latitude and longitude values for each perimeter point appear in the Points list.

Point entry

Use the Point Entry pane to add, delete, or change the sensor pattern's perimeter points.

You can also define the sensor pattern by clicking the perimeter points in the 2D Graphics window while the Pattern Tool window is open.

Add perimeter points

Use the following steps to create data points for the perimeter. One row of values describes a single point in the sensor pattern.

  1. Click Insert Point.
  2. In the new row that appears in the grid, enter the latitude and longitude or azimuth and elevation values for the point.
  3. Repeat steps 1 and 2 for each new point. A minimum of three points are required to create a pattern. If necessary, STK will automatically add a point to close the contour to the point list. This point will be the same as the first point in the list.

Change perimeter points

Double-click the value that you want to change in the Points list. Then enter the new value.

Delete perimeter points

To delete one point, select the point that you want to delete from the Points list and click Delete Point.

To delete all points from the Points list, click Delete All Points.

The following diagram illustrates a custom pattern sensor shaped like an arrow:

Saving custom sensor patterns

Click Save... to the right of the Custom Pattern File Name option. Specify the path and name of the file to which you wish to save the pattern information.

STK creates an ASCII text file (*.Pattern) based on the points you entered when you created or edited the sensor pattern.