Coverage Trade Study in Mountainous Terrain

STK Premium (Air), STK Premium (Space), or STK Enterprise
You can obtain the necessary licenses for this tutorial by contacting AGI Support at support@agi.com or 1-800-924-7244.

For this lesson, you need to install STK's Analyzer capability. It is included in the STK Premium software download, but you must install it separately from the main STK application.

This tutorial requires an internet connection and STK 12.9 or newer to complete in its entirety. If you have an earlier version of STK, you can view a legacy version of this lesson.

The results of the tutorial may vary depending on the user settings and data enabled (online operations, terrain server, dynamic Earth data, etc.). It is acceptable to have different results.

Capabilities covered

This lesson covers the following STK Capabilities:

  • STK Pro
  • Coverage
  • STK Analyzer

Problem statement

The Mount Saint Helens Worm Flows Route, from Marble Mountain Sno-Park, is the most direct route to the summit of Mount St. Helens during the winter season. Four ranger stations are used to perform visual observations of the trail. At times, only two stations are manned. You want to know which two observation posts, together, have the best percentage of visual coverage on the trail.

Solution

Build an STK scenario that analyzes the coverage of the four ranger stations used to monitor the Mount Saint Helens Worm Flows Route. Use STK's Analyzer capability to perform a coverage analysis of the exercise area using all possible combinations of two of the four different station locations. Determine which combination of two stations provides the greatest percentage coverage along the hiking trail.

What you will learn

Upon completion of this tutorial, you will understand how to:

  • Set up Analyzer
  • Use the Design of Experiments Tool

Watch the following video. Then follow the steps below, which incorporate the systems and missions you work on (sample inputs provided).

Creating a new scenario

First, you must create a new STK scenario; then build from there.

  1. Launch STK ().
  2. Click Create a Scenario in the Welcome to STK dialog box.
  3. Enter the following in the STK: New Scenario Wizard:
    4. Option Value
    Name: Ranger_Stations
    Location: Default
    Start: Default
    Stop: Default
  4. Click OK when you finish.
  5. Click Save () when the scenario loads. STK creates a folder with the same name as your scenario for you.
  6. Verify the scenario name and location in the Save As window.
  7. Click Save.

Save () often during this lesson!

Disabling Terrain Server

You're going to use a local terrain file for analysis. Turn off Terrain Server.

  1. Right-click Ranger_Stations () in the Object Browser.
  2. Select Properties ().
  3. Select the Basic - Terrain page.
  4. Clear the Use terrain server for analysis check box in the Terrain Server frame.
  5. Click OK to accept your changes and close the Properties Browser.

Adding terrain

Load analytical terrain.

  1. Bring the 3D Graphics window to the front.
  2. Click Globe Manager () in the 3D Graphics window toolbar.
  3. Click Add Terrain/Imagery () on the Globe Manager Hierarchy toolbar.
  4. Select Add Terrain/Imagery... () in the shortcut menu.
  5. Click the Path: ellipsis () when the Globe Manager: Open Terrain and Imagery Data dialog box opens.
  6. Go to <STK install folder>\Data\Resources\stktraining\imagery.
  7. Click OK.
  8. Select the StHelens_Training.pdtt check box.
  9. Click Add .
  10. Click Yes when prompted to Use Terrain for Analysis.

Using a KMZ file in your scenario

In Globe Manager, you can use the KML window to add Keyhole Markup Language (KML) files (.kml/.kmz) to a 3D Graphics window. You can choose to display or hide the features specified in the KML files, and you can zoom to them using the KML window shortcut menu. As stated earlier, you are performing analysis along the Mt. Saint Helens Worm Flows Climbing Route. You would like to view the route as a model in the 3D Graphics window. You have a KMZ file that models the Mt. Saint Helens Worm Flows Climbing Route. You can use the STK Globe Manager to inlay the KML file for visualization in the 3D Graphics window. After you visualize the KMZ in STK, you can import it as an object to use for your analysis.

  1. Select the KML tab in Globe Manager.
  2. Click Open KML Content () in the KML toolbar.
  3. Go to <STK install folder>\Data\Resources\stktraining\KML.
  4. Select MtStHelens.kmz.
  5. Click Open .

Importing MtStHelens.kmz as an STK object

Turn your KML item into an STK object.

  1. Right-click Mount Saint Helens Worm Flows Route in Globe Manager.
  2. Select Import as Line Target.

Showing surface lines

Have STK display surface lines on terrain data whenever it is available from any source.

  1. Open Ranger_Stations () Properties ().
  2. Select the 3D Graphics - Global Attributes page.
  3. Open the On Terrain: shortcut menu in the Surface Lines frame.
  4. Select On.
  5. Click OK to accept your changes and to close the Properties Browser.
  6. Bring the 3D Graphics window to the front.
  7. Right-click Mount Saint Helens Worm Flows Route () in the Object Browser.
  8. Select Zoom To.

Mount Saint Helens Worm Flows Route

Building the first ranger station

There are four ranger stations along the hiking trail. The observation platforms are fifty feet high. You will build the first ranger station and then reuse it to create the other three ranger stations. By using Copy and Paste, all you will have to do is change the locations of the remaining three ranger stations.

  1. Select Place () in the Insert STK Objects tool ().
  2. Select the Define Properties () method.
  3. Click Insert...
  4. Set the following options on the Basic - Position page:
    5. Option Value
    Latitude 46.1488 deg
    Longitude -122.177 deg
    Height Above Ground 50 ft
  5. Click Apply to accept your changes and keep the Properties Browser open.
  6. Right-click Place1 () in the Object Browser.
  7. Select Rename.
  8. Rename Place1 () to Station1.

Setting your constraints

Use your analytical terrain source to set viewing constraints.

  1. Select the Constraints - Active page.
  2. Clear Enable - Line Of Sight in the Active Constraints list.
  3. Click Add new constraints () in the Active Constraints toolbar.
  4. Select Terrain Mask in the Constraint Name list in the Select Constraints to Add dialog box.
  5. Click Add.
  6. Click Close to close the Select Constraints to Add dialog box.
  7. Click OK to accept your changes and to close the Properties Browser.

Creating three more ranger stations

Using copy and paste, you can insert three more ranger stations into the scenario. You will only need to change their latitudes and longitudes.

  1. Select Station1 () in the Object Browser.
  2. Click Copy () in the Object Browser toolbar.
  3. Click Paste () three times in the Object Browser toolbar.
  4. One at a time, open the properties of Stations two through four and make the following property changes on their Basic - Position page:
    5. Station Latitude Longitude
    Station2 46.1412 deg -122.165 deg
    Station3 46.1638 deg -122.184 deg
    Station4 46.1606 deg -122.174 deg

Decluttering labels

Use Label Declutter to separate the labels of the ranger stations and make them easier to see in the 3D Graphics window.

  1. Bring the 3D Graphics window to the front.
  2. Click Properties () in the 3D Graphics window toolbar.
  3. Select the Details page in the Properties Browser.
  4. Select Enable in the Label Declutter frame.
  5. Click OK to accept your changes and to close the Properties Browser.

Viewing the Worm Flows route and the ranger stations

  1. Bring the 3D Graphics window to the front.
  2. Right click on Station1 () in the Objects Browser
  3. Select Zoom To.
  4. Use your mouse's scroll wheel or right button to zoom out until you can see the Worm Flows Route and all four stations.

Defining the Grid Area of Interest

You want to assess the coverage of any two of the four nodes along Mount Saint Helens Worm Flows Route. The Coverage Definition () object defines a coverage area for analysis. Coverage analysis is based on the accessibility of assets (objects that provide coverage) and geographical areas. Define the location of a coverage grid.

  1. Insert a Coverage Definition () object using the Insert Default () method.
  2. Open CoverageDefinition1's () properties ().
  3. Select the Basic - Grid page.
  4. Select Custom Boundary as the Type for the Grid Area of Interest.
  5. Click Select Boundaries ....
  6. Move () Mount_Saint_Helens_Worm_Flows_Route () from the Boundary Objects list to the Selected Objects list in the Select Boundaries... dialog box.
  7. Click OK to close the Select Boundaries... dialog box.

Setting the Grid Definition

The statistical data computed during a coverage analysis is based on a set of locations, or points, that span the specified grid area of interest.

  1. Select Distance in the Point Granularity shortcut menu in the Grid Definition frame.
  2. Enter 10 ft in the Distance field.

Setting the altitude of the grid points

Place the grid points to 5 feet above the terrain.

  1. Select Altitude above Terrain in the Point Altitude shortcut menu.
  2. Enter 5 ft in the Altitude above Terrain field.
  3. Click Apply to accept your changes and keep the Properties Browser open.

Setting your grid constraints

Use the constraints you applied to Station1 () across the coverage grid.

  1. Click Grid Constraint Options....
  2. Select Place in the Reference Constraint Class shortcut menu in the Grid Constraint Options dialog box.
  3. Select Use Object Instance.
  4. Select Station1.
  5. Click OK to close the Grid Constraint Options dialog box.
  6. Click Apply to accept your changes and keep the Properties Browser open.

Selecting your coverage assets

Assets properties enable you to specify the STK objects you want to use to provide coverage.

  1. Select the Basic - Assets page in the Coverage Properties Browser.
  2. Select all four Place () objects in the Assets list.
  3. Click Assign.
  4. Click Apply to accept your changes and keep the Properties Browser open.

Setting an interval

For your scenario, you have static assets covering a static area. If you compute the coverage over the whole scenario time, that would be a waste of computations. None of the objects will change positions over time, so you can shorten the computation time.

  1. Select the Basic - Interval page.
  2. Open the Interval: shortcut menu in the Access Interval frame.
  3. Select Replace With Times.
  4. Type +1 sec in the Stop: field.
  5. Click Apply to accept your changes and keep the Properties Browser open.

Turning off automatic recomputing

Advanced properties enable you to adjust the manner in which STK stores and computes access information. Although it is not required, the possibility exists that after computing coverage, you might change the properties of an asset. Therefore, set up the Coverage Definition object to enable you to manually compute coverage.

  1. Select the Basic - Advanced page.
  2. Clear Automatically Recompute Accesses.
  3. Click Apply to accept your changes and keep the Properties Browser open.

Showing 2D Graphics coverage grid

Later in the scenario, you will display color contours along the route. In order to better visualize the contour colors, remove the grid points along the route.

  1. Select the 2D Graphics - Attributes page.
  2. Clear Show Points in the Grid frame.
  3. Click OK to accept your changes and close the Properties Browser.

Computing Accesses tool

The Compute Accesses tool enables you to compute accesses between the grid points and the assigned assets.

  1. Select CoverageDefinition1 () in the Object Browser.
  2. Select CoverageDefinition in the Menu bar.
  3. Select Compute Accesses in the shortcut menu.

Creating Coverage Figure of Merit

The Coverage Figure of Merit () object enables you to analyze coverage in various directions over time, using several attitude-dependent figures of merit.

  1. Insert a Figure of Merit () object using the Insert Default () method.
  2. Select CoverageDefinition1 () in the Select Object dialog box.
  3. Click OK.

Measuring number of assets

Prior to running a trade study in Analyzer, determine how much of the route can be observed when utilizing all four stations. N Asset Coverage measures the number of assets available simultaneously during coverage.

  1. Open FigureOfMerit1's () properties ().
  2. Select the Basic - Definition page.
  3. Select N Asset Coverage for the Definition - Type.
  4. Set the following in the Satisfaction frame:
    5. Option Action
    Enable On
    Satisfied if Greater Than
    Threshold 0
  5. Click Apply to accept your changes and keep the Properties Browser open.
    6.  

Generating Figure of Merit percent satisfied report

You want to determine the overall percentage of coverage along the route when all of the ranger stations are manned. The Percent Satisfied report presents the percentage of the total grid area and actual area where the static value of the Figure Of Merit meets the specified satisfaction criterion.

  1. Right-click FigureOfMerit1 () in the Object Browser.
  2. Select Report & Graph Manager... () in the shortcut menu.
  3. Select the Percent Satisfied () report in the Styles listin the Report & Graph Manager.
  4. Click Generate....
  5. Note that the approximate percent satisfied is 93.

    6. One result is the percentage of coverage along the route when using all four stations. You'll compare this number to your analysis when using Analyzer.

  6. Close the report and the Report & Graph Manager.

Creating static contours

You can specify how levels of coverage quality display in both the 2D and 3D Graphics windows. To accurately display contour levels for figures of merit in the 2D and 3D Graphics window, you should know the approximate range of values for the current Figure Of Merit. You have four stations in your coverage analysis. Based on your Percentage Satisfied report, you don't have 100% coverage. There are obvious gaps in the coverage, so you need to create a contour range.

Turning off animation graphics

  1. Return to the Figure of Merit () object's properties ().
  2. Select the 2D Graphics - Animation page.
  3. Clear Show Animation Graphics.
  4. Click Apply to accept your changes and keep the Properties Browser open.

Creating contours

  1. Select the 2D Graphics - Static page.
  2. Select the Markers option in the Show Points As frame.
  3. Leave the default marker as is.
  4. Select the Show Contours option in the Display Metric frame.
  5. Click Remove All in the Level Attributes frame.
  6. Set the following in the Level Adding frame:
    7. Option Value
    Start 0
    Stop 4
    Step 1
  7. Click Add Levels .
  8. Ensure Color Ramp is selected in the Color Method shortcut menu.
  9. Set the following:
    10. Option Value
    Start Color Red
    End Color Blue
  10. Click Apply to accept your changes and to keep the Properties Browser open.

Displaying contour legends

The Legend option provides you with a convenient way to interpret contour data displayed in the 2D and 3D Graphics windows. In this instance, you cannot view the Line Target () object contours in the 3D Graphics window.

  1. Click Legend... .
  2. Click Layout... in the Static Legend for FigureOfMerit1 dialog box.
  3. Select Show at Pixel Location in the 2D Graphics Window frame in the Figure of Merit Legend Layout dialog box.
  4. Enter 0 in the Number Of Decimal Digits field in the Text Options frame.
  5. Click OK to close the Figure of Merit Legend Layout dialog box.
  6. Close the Static Legend for FigureOfMerit1 dialog box.
  7. Click OK to accept your changes and to close the Properties Browser.
  8. Bring the 2D Graphics window to the front. You should see the legend in the window.
  9. Using your mouse, zoom in to the Worm Flows Route.

    10. You should see the color contours representing how many stations can simultaneously observe that portion of the route.

    Color Contours

Using Analyzer

Analyzer automates STK trade studies and parametric analysis by blending the engineering analysis capabilities of Ansys ModelCenter with AGI's STK software suite. Through its integration with the STK GUI and by using its own toolbars, Analyzer eliminates the need for scripts or programming.

Now that you have determined the static coverage values for the route, run a trade study to determine which two nodes will result in the least degradation.

  1. Select the View menu at the top of STK.
  2. Select Toolbars in the first-level menu.
  3. Select Analyzer in the second-level menu.
  4. Click Analyzer... () in the Analyzer toolbar.

Assigning STK Variables and Property Variables (Inputs)

Use the Analyzer Main Form to configure input and output variables available for further analysis.

  1. Select CoverageDefinition1 () in the STK Variables list.
  2. Select the General tab in the STK Property Variables frame.
  3. Expand () Assets ().
  4. Expand () Place/Station1 () through Place/Station4 ().
  5. Double-click all four Status () variables, one at a time, to move them to the Analyzer Variables list.

Assigning Data Provider Variables (Outputs)

Output variables are listed in the Data Providers, Object Coverage, or DeckAccess tab of the Outputs group.

  1. Select FigureOfMerit1 () in the STK Variables list.
  2. Select the Data Providers tab in the Data Provider Variables frame.
  3. Expand () Static Satisfaction ().
  4. Double-click Percent Satisfied () to move it to the Analyzer Variables list.

    5. You now have the required inputs and outputs for the trade study.

    Analyzer Variables

Using the Design of Experiments tool

You can use the Design of Experiments (DOE) tool to create and perform tables of runs for a scenario. You can either use a classical design type, such as a Full Factorial design, or supply your own custom table of runs. For this exercise, you need to cover all possibilities of two stations being manned and two stations being unmanned. You are determining which pair of stations will provide the highest percentage of coverage.

  1. Click Design of Experiments Tool... () in the Analyzer tool bar.
  2. Select the Variables tab when the DOE Tool opens.
  3. Drag and drop each Place_Station Status () from the components list, in order (1-4), to the Design Variables list.

    4. Design Variables List

  4. Drag and drop Percent_Satisfied () from the Components list to the Responses list.

    5. Response Variable

Creating a Design Table

The Design Table section contains tools for editing design matrices. You can directly edit values, add runs, and delete runs. You can save these edited designs for later recall or for import from lists of comma-separated values. If you look at the default table, there are multiple runs. Each Status column represents a station. You do not need to manually enter values into the table. You only need to delete each run that does not have a combination of two eInactive and two eActive cells.

  1. Select the Design Table tab.
  2. Highlight and click Delete () for run(s) that do not have a combination of two eInactive and two eActive cells. When you have completed the design table, you should have a total of six runs (scenarios) that cover each possibility of two stations active and two stations inactive.

    3. Completed Design Table

  3. Click Run... to run the analysis.

    4. When the run is complete, look at the Data Explorer. You can see which run has the highest percentage of coverage. Based on the following picture, you can see that when stations two and four (eActive) are manned, they present the highest percentage of visual observation along the trail. Therefore, on days that only allow for manning two ranger stations, stations two and four are the best choice.

    Table

  4. Make a note of which two ranger stations resulted in the highest percentage of coverage (e.g. 2 and 4).
  5. Close the Data Explorer.
  6. Click No when the Save dialog box opens.
  7. Close the DOE Tool.
  8. Close Analyzer.

De-assigning stations one and three

Using the run that resulted in the highest percentage of coverage along the route, you can change the Coverage Definition () object assets and the Figure of Merit () contours to reflect and visualize the coverage along the route.

  1. Return to STK.
  2. Open CoverageDefinition1's () properties ().
  3. Select the Basic - Assets page when the Properties Browser opens.
  4. Select all four Assets in the Assets list.
  5. Click De-assign.
  6. Select Station2 () and Station4 ().
  7. Click Assign.
  8. Click OK to accept your changes and to close the Properties Browser.
  9. Read the information warning and close the Analyzer Variables dialog box.

Viewing the results

Bring the 2D Graphics window to the front to view the overall coverage using just Station2 () and Station4 ().

Station 2 and station 4 coverage

Summary

This tutorial introduced you to Analyzer and the Design of Experiments Tool. There are four ranger stations that park rangers use to monitor the Mount Saint Helens Worm Flows Route. Often, only two stations can be manned. You used STK to determine which two stations provide the highest percentage of visual coverage. You accomplished this by doing the following:

  • Applied a local analytical terrain file (.pdtt) to your analysis

  • Inserted four Place () objects into the scenario at the locations of the ranger stations

  • Converted a KMZ file into a Line Target () object that modeled the Mount Saint Helens Worm Flows Route

  • Set up a Coverage Definition () object to obtain the percentage of the Worm Flows Route that is visible to all four ranger stations

  • Used Analyzer's Design of Experiments tool to create a design table and determined that ranger stations two and four provide the most coverage along the Worm Flows Route when park rangers can only man two stations

Saving your work

  1. Close any open reports, properties, and the Report & Graph Manager.
  2. Save () your work.