To evaluate the quality of coverage to a single object in the Systems Tool Kit® (STK®) application, you can use the Coverage Tool, which is available from the Analysis menu. This tool is available for facilities, places, radars, receivers, sensors, targets, transmitters, and vehicles. Use the single-object coverage method to determine coverage if you are interested in coverage of a small number of well-defined locations or along the trajectory of a moving object.
For instance, you may wish to calculate single-object coverage to track the position of a truck along a known road in the Colorado Rocky Mountains. You know that you can receive position information using the GPS receivers, but you do not know if the quality of coverage is adequate over the course of the road. To determine the accuracy of the GPS receivers over that road, you would first define a ground vehicle with a great arc path corresponding to the path of the road. Next, you would add all of the satellites in the GPS constellation to the scenario. Finally, you would open the Coverage tool for the ground vehicle and assign the GPS satellites as assets for that object. You may also define a Figure Of Merit type to the object to better define the quality of coverage. In this instance, you would choose a dilution of precision (DOP) Figure Of Merit type, then review the value of the DOP as the truck travels along the road.
The main differences between normal and single-object coverage are:
- You can use single-object coverage to analyze objects with time-dependent positions.
- You can only analyze one Figure Of Merit at a time using single-object coverage.
Specifying an access interval
First, you will need to specify the Interval or Start and Stop times to be used to calculate coverage. By default, these times correspond to the period of the object in the case of vehicles or vehicle subobjects. For facilities, places, targets, or their subobjects, the times correspond to the scenario's time period. For more information on the options available for time intervals and start and stop times, see Time Options.
Choosing assets for use in computing coverage
To determine coverage for a single object, you must assign one or several assets to be used in coverage computations. For single-object coverage, it is important to have a clear understanding of the asset time periods. The time period for the coverage analysis is constructed as the intersection of the reference object time period and the asset time period. Assets are used to calculate whether coverage to the object can be achieved. If you define a Figure Of Merit for the coverage, coverage to the object from the assets is measured by the Figure Of Merit values.
Coverage processing does not verify that assets are defined during the specified access interval.
Assigning assets for an object
The Assets list, on the left side of the Coverage window, contains a list of assets that you can assign to the Coverage object. If an object in the list appears in bold with an asterisk (*) to the left of its name, it is currently assigned to the coverage object. Objects that you can assign as assets to the Coverage object are all types of vehicles and sensors, as well as chains, constellations, radars, receivers, and transmitters.
To assign an asset to the Coverage object, highlight the object in the Assets list, then click . To remove an item from the Assets list, select it and click .
When assigning a Constellation, Satellite Collection, or a Chain object containing constellations as an Coverage asset, use the drop-down menu with selection of Grouped and Separate. You can then characterize all objects in the Constellation or Satellite Collection object as a single asset (Grouped) or as separate assets (Separate). For more information, see Using Grouped Assets.
Activating and deactivating assets for an object
After STK processing computes accesses, you can change the status of each asset in the Assets list from Active to Inactive or vice versa. This enables you to remove selected assets from consideration without removing access information from the coverage calculations. You can use the Inactive option to simulate the effect of an asset failure on the coverage provided by a set of satellites.
Computing coverage for an object
Once you have assigned assets for the object and defined the quality of coverage expected, click to compute coverage for the object.
When the STK software computes coverage for the object, it also computes the static value for the Figure Of Merit type you chose and displays the coverage graphics, if you enabled them. STK processing automatically computes access to support coverage analysis if you generate any of the standard Coverage reports or graphs.
Clearing single-object coverage and access computations
You can clear the coverage definition of the selected object by clicking in the Coverage window. You can clear the access definition of the selected object by clicking . You may want to clear these to free up memory associated with the coverage analysis or when you wish to define a new coverage problem.
If you have already closed the Coverage window, you can select Remove All Object Coverages from the Analysis menu. The Remove All Object Coverages tool removes coverage for all the objects in the scenario.
Defining the quality of coverage
You can evaluate the quality of coverage for an object by choosing the method for computing coverage, setting measurement options, and identifying the criterion needed to achieve satisfactory coverage. By default, all single-object coverages are defined with a simple coverage Figure Of Merit type. The field to the right of the button displays the FOM type selected. Beneath the FOM type is the value of the Figure Of Merit for the selected object. This value changes if you redefine the Figure Of Merit or choose a different FOM type. If you wish to calculate coverage using a different FOM type, click in the Figure of Merit of the Coverage window.
In the Specify Figure of Merit window, you can change the default Figure Of Merit type from Simple Coverage to a number of other types. The fields in this window enable you to choose the type and criteria for the object's Figure Of Merit.
Displaying the quality of coverage in a graphics window
Once you have defined the Figure Of Merit, you can set the display of coverage levels in the 3D Graphics window using the options in the Graphics area of the Coverage Tool window.
Quality of coverage graphics options
| Option | Description |
|---|---|
| Show Marker Animation Highlight | If this check box is selected, the STK UI will display graphics providing a highlight around the normal object marker and update the highlight during animation. |
| Show FOM Graphics on Vehicle Track | If this check box is selected and Satisfaction is selected or contours are defined, the STK UI will display graphics providing a persistent display of time-dependent information about the Figure Of Merit. This option is only available if the STK software is calculating coverage from a vehicle object. |
| / | This button is labeled Display Options if the Figure Of Merit is Simple Coverage or Access Separation, or Satisfaction for other figures of merit. It opens the Object Coverage Graphics window, where you can define the display graphics for coverage satisfaction. |
| This button opens the Contours window, where you can specify how levels of Figure Of Merit values will be displayed in the graphics window. This button is not available if the Figure Of Merit is Simple Coverage or Access Separation. |
Coverage graphics depend on the dynamic definition of the Figure Of Merit. If the Figure Of Merit has no dynamic definition, nothing will appear in the 3D Graphics window.
Saving object coverage
Selecting the Save Configuration check box tells the STK application to save the single-object coverage definitions when the scenario is saved to disk, assuming that you already computed coverage.