Part 6: Introduction to the Pro Capabilities

STK Pro, 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.

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.

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

Credits: ISERV, NASA

Capabilities covered

This lesson covers the following STK Capabilities:

  • STK Pro

Problem statement

Engineers and operators require a quick way to determine if local terrain is affecting visibility between ground sites and satellites for a variety of purposes such as communications, imaging, and general situational awareness. In this tutorial, there is a GPS monitoring station in the vicinity of Mount St. Helens. A USGS Digital Elevation Model (DEM) file contains terrain data for the area requiring analysis. Raw satellite imagery is available of Mount St. Helens which will provide situational awareness of the analytical area when converted as an inlay. A further need exists to create color elevation imagery of the area to be used in a briefing and in documentation.

Solution

Using STK, load a DEM file to analyze the impact of local terrain on accesses between a ground station and GPS satellites. Create a color elevation image, and convert a raw satellite image that can be used as an inlay for visualization and situational awareness. Change the DEM file into a STK Terrain File (pdtt) which can be used to visualize terrain in the 3D Graphics window.

What you will learn

Upon completion of this tutorial, you will be able to:

  • Use local terrain files for analysis
  • Create images from terrain data that show elevation data colored by height
  • Convert a single image into a format that can be displayed in the 3D Graphics window
  • Create terrain inlays for a specific region
  • Model a Constellation object
  • Model a Chain object

Video guidance

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

Create a new scenario with a run time of 24 hours.

  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:

    STK_Pro
    Start: Default
    Stop: Default
  4. When you finish, click OK.
  5. When the scenario loads, click Save (). A folder with the same name as your scenario is created for you.
  6. Verify the scenario name and location in the Save As window.
  7. Click Save.

Save () often!

Locating the U.S. Geological Survey DEM file

The DEM file used in this tutorial is located in the install directory. Take a moment to download the file. DO NOT unzip the folder. Follow the instructions in the tutorial to use the file.

  1. Create a folder on your Desktop called Terrain.
  2. Using File Explorer, browse to the location of the DEM file using the following:
    • STK 11: C:\Program Files\AGI\STK 11\CodeSamples\CodeSamples.zip\SharedResources\Scenarios\Events
    • STK 12: C:\Program Files\AGI\STK 12\CodeSamples\CodeSamples.zip\SharedResources\Scenarios\Events
  3. Locate and copy the file named hoquiam-e.dem.
  4. Paste the hoquiam-e.dem file into the Terrain folder you created on your desktop.

Using the DEM file for analysis and visualization

The Pro capability adds realism to system models. Building on the fundamental capabilities of STK, Pro introduces more sophisticated modeling through advanced access constraints, flexible sensor shapes, complex visibility links, more object tracks and digital terrain data.

Load the locally available DEM terrain data file to be used for analysis and visualization into the scenario.

  1. Right click on STK_Pro () in the Object Browser.
  2. Select Properties ().
  3. Select the Basic - Terrain page when the Properties Browser opens.
  4. Clear Use terrain server for analysis.

    5. You're using a local terrain file for both analysis and visualization. By turning off streaming terrain, you are simulating what you'd see in a setting that doesn't have an Internet connection.

  5. Click Add in the Custom Analysis Terrain Sources: frame.
  6. Open the file type shortcut menu.
  7. Select USGS DEM (DEM).
  8. Browse to the Terrain folder on your desktop that contains the hoquiam-e.dem file.
  9. Select hoquiam-e.dem.
  10. Click Open.
  11. Click OK to accept your changes and to close the Properties Browser.

Displaying a background image and inlay in the 2D Graphics window

  1. Bring the 2D Graphics window to the front.
  2. Click Properties () in the 2D Window Defaults tool bar.
  3. Select the Imagery page when the Properties Browser opens.
  4. Select the Image File: option.
  5. Ensure Basic.bmp is selected (default).

Displaying borders and terrain extents in the 2D Graphics window

Outline international borders and all the states of the United States and provinces of Canada:

  1. Select the Details page.
  2. Click on and highlight the following (leave RWDB2_Coastlines highlighted) in the Map Details field:
    • RWDB2_International_Borders
    • RWDB2_Provincial_Borders

    Create a yellow outline of the extent of the hoquiam-e.dem file's location:

  3. Select the Show Extents check box in the Terrain Regions Display frame.
  4. Click OK to accept your changes and to close the Properties Browser.

Viewing your changes in the 2D Graphics window

  1. Bring the 2D Graphics window to the front.
  2. Zoom in () to the state of Washington.

    3. The yellow box in the southwest corner of the state is the location of the hoquiam-e.dem file. Analysis inside the box can be done using local terrain. Analysis outside the box will take place on the WGS84.

    Show Extents

  3. Zoom in () to the terrain extents and move it to the right of your map.

Creating a color elevation image

The Create Color Elevation Imagery utility allows you to create images from terrain data that show elevation data colored by height (for example, blue for sea level, green for land, and white for mountain tops). This is useful if you need to visualize terrain but lack imagery or if you want to put the emphasis on height rather than the content of the image.

  1. Open the Utilities menu.
  2. Select Create Color Elevation Imagery.
  3. Move the Create Color Elevation Imagery utility next to the terrain region display in the 2D Graphics window.46
  4. Enter the following extents which match the hoquiam-e.dem extents:
    5. Option Value
    North Lat 47 deg
    West Lon -123 deg
    East Lon -122 deg
    South Lat 46 deg
  5. Click Get Min/Max Alt.

    6. Displays the minimum and maximum altitude values of the region selected in the 2D Graphics window. This range can help if you use explicit colors. Set HSV for the rendering of elevation data during the conversion process. The resulting image is colored so that elevations are drawn with a linearly interpolated color between the minimum altitude and the maximum altitude, depending on the elevation. Change the minimum altitude values. The default values create a dark blue color. You are landlocked so use a corresponding HSV code that removes the blue.

  6. Set the following Min Altitude: values in the Color Options frame:
    7. Option Value
    Hue 0.25
    Saturation 0.75
    Value 0.20
  7. Select the JPEG 2000 Image (jp2) Format: in the Output File frame.
  8. Click the Directory: ellipses ().
  9. Browse to the location of your scenario (e.g. C:\Users\username\Documents\STK 12\STK_Pro).
  10. Click Select Folder.
  11. Type StHelensColor in the Filename: field.
  12. Click Convert.
  13. Close the Create Color Elevation Imagery utility.

Displaying the image using 2D Graphics Imagery

2D Graphics Imagery is used to display a background image and inlay images in 2D Graphics windows.

  1. Bring the 2D Graphics window to the front.
  2. Open the 2D Graphics window properties ().
  3. Select the Imagery page.
  4. Click Add... in the Inlay Images frame.
  5. Select StHelensColor.jp2 in the Map Images dialog box.
  6. Click Open.
  7. Click OKto accept your changes and to close the Properties Browser.

Viewing the inlaid image in the 2D Graphics window

  1. Bring the 2D Graphics window to the front.

    2. Lower elevations are darker in color and higher elevations are lighter in color. Mount St. Helens sticks out as the highest point in the image.

color elevation imagery

Converting an image and terrain data to a 3D image

Use the Imagery and Terrain converter to convert a single image, with or without terrain data, into a format that can be displayed in a 3D Graphics window. The image is converted to a pdttx or jp2 file (image inlay) and the terrain data is converted to a pdtt file (terrain inlay).

Converting an image using the Imagery converter

Convert an ISS SERVIR Environmental Research and Visualization System (ISERV) LEVEL-R (RAW) imagery .jpg into JPEG 2000 Image (jp2) inlay.

  1. Open the Utilities menu.
  2. Select Imagery and Terrain Converter.
  3. Select the Single Image page when the Properties Browser opens.

Selecting the image Input Data

Select the image file to be converted.

  1. Click the Image Filename: ellipsis () in the Input Data frame.
  2. Browse to the location of the ISERV imagery (Typically, <STK install folder>\Data\Resources\stktraining\imagery\) in the File dialog box.
  3. Select ISERV_Imagery.
  4. Click Open.
  5. Select the file named IPR201407092040194622N12217W.JPG.
  6. Click Open.

    7. The extents are automatically read from the metadata contained in the supporting files and entered into the Image: fields located in the Image Extent frame.

Setting the image Output Data

You can select a JPEG 2000 image.

  1. Set the following in the Output Data / Image file frame:
    2. Option Value
    Format: JPEG 2000 Image (jp2)
    Directory: Location of the scenario (e.g. C:\Users\username\Documents\STK 12\STK_Pro
    Filename: ISERV_StHelens
  2. Click Convert.

Creating a terrain inlay using the Terrain Region converter

Use the Terrain Region converter to create terrain inlays (pdtt files) for a specific region. Select your input data.

  1. Select the Terrain Region page.
  2. Open the Terrain Source: shortcut menu in the Input Data frame.
  3. Select the path to the hoquiam-e.dem file.

Setting the terrain Output Data

  1. Set the following in the Output Data frame:
    2. Option Value
    Directory: Location of the scenario (e.g. C:\Users\username\Documents\STK 12\STK_Pro
    Filename: StHelensTerrain
  2. Click Convert.
  3. Click Close to close the Imagery and Terrain Converter when finished.

Adding terrain and imagery files in Globe Manager

Globe Manager allows you to customize scenario globes with imagery and terrain data as well as manage that data once it has been applied. The Hierarchy window is used to add central bodies, image, and terrain items to a scenario.

  1. Bring the 3D Graphics window to the front.
  2. Click Globe Manager () in the Globe Manager toolbar.
  3. Click Add Terrain/Imagery () In the Hierarchy toolbar.
  4. Select Add Terrain/Imagery... (Add Terrain/Imagery button) in the shortcut menu.

Selecting the files to display in the 3D Graphics window

You can use the Globe Manager: Open Terrain and Imagery Data dialog box to select imagery and terrain data to display in the 3D Graphics window.

  1. Open the Path: shortcut menu when the Globe Manager: Open Terrain and Imagery Data dialog box opens.
  2. Select the path to your scenario (e.g. C:\Users\username\Documents\STK 12\STK_Pro).
  3. Select both the Image (ISERV_StHelens.jp2) and Terrain files (StHelensTerrain.pdtt).
  4. Click Add.
  5. Select No in the Use Terrain for Analysis dialog box.

    6. You're already using the hoquiam-e.dem file for analysis.

Viewing the terrain and imagery files in the 3D Graphics window

  1. Right-click on ISERV_StHelens.jp2 in Globe Manager.
  2. Select Zoom To.
  3. Use your mouse to view the image and surrounding terrain.

    4. ISERV imagery and local terrain

    You can see the satellite image ISERV_StHelens.jp2 which is placed on top of the StHelensTerrain.pdtt. Terrain outside of the image is still visible. If desired, you can return to Globe Manager and turn Aerial.ve back on to use Bing Maps. You can also, toggle ISERV_StHelens.jp2 or StHelensTerrain.pdtt on and off to see the visual difference. The ISERV_StHelens.jp2 image can also be used as an inlay in the 2D Graphics window.

  4. When finished, ensure the ISERV_StHelens.jp2 and StHelensTerrain.pdtt are turned on.

Inserting the GPS Tracking Device

Insert a Place () object which will simulate the GPS satellite tracking device.

  1. Select Place () in the Insert STK Objects tool.
  2. Select the Insert Default () method.
  3. Click Insert... .
  4. Right click on Place1 () in the Object Browser.
  5. Select Rename in the shortcut menu.
  6. Rename Place1 () to TrackingDevice.
  7. Open TrackingDevice's () properties ().
  8. Select the Basic - Position page when the Properties Browser opens.
  9. Set the following:
    10. Option Value
    Latitude: 46.204 deg
    Longitude: -122.188 deg
    Height Above Ground: 5 ft

    Height Above Ground represents the height of the tracking device's antenna.

  10. Click Applyto accept your changes and to keep the Properties Browser open.

Defining an Azimuth-Elevation Mask

The AzElMask properties enable you to define an azimuth-elevation mask for the GPS tracking device.

  1. Select the Basic - AzElMask page.
  2. Set the following:
    3. Option Value
    Use: Terrain Data
    Use Mask for Access Constraint Select
  3. Click Applyto accept your changes and to keep the Properties Browser open.

    4. Selecting Terrain Data automatically creates and stores an azimuth-elevation (Az-El) mask file, which is an ASCII text file that is formatted for compatibility with STK and ends in an .aem extension, into your scenario folder. Turning on Use Mask for Access Constraint enables the Az-El Mask constraint located on the Constraints - Basic page. Using the Az - El Mask constraint constrains access to the object by azimuth-elevation masking which is a 360 degree field of view around the object being constrained.

Displaying the Azimuth-Elevation Mask

For situational awareness, you can display the Azimuth-Elevation Mask in both the 2D Graphics and 3D Graphics windows.

  1. Select the 2D Graphics - AzElMask page.
  2. Set the following At Range properties:
    3. Option Value
    Show Select
    Number of Steps: 10
    Minimum Range: 0 km
    Maximum Range: 50 km
  3. Click OKto accept your changes and to close the Properties Browser.

Viewing the Azimuth Elevation Mask in the 3D Graphics window

  1. Bring the 3D Graphics window to the front.
  2. Click Properties () in the 3D Window Defaults toolbar.
  3. Select the Details page when the Properties Browser opens.
  4. Select Enable in the Label Declutter frame.
  5. Click OKto accept your change and to close the Properties Browser.

    6. Label Declutter is used to separate the labels on objects that are in close proximity for better identification in small areas. It also keeps object labels from being hidden by terrain.

  6. Right-click on TrackingDevice () in the Object Browser.
  7. Select Zoom To in the shortcut menu.
  8. Using your mouse, zoom out until you can see the visual representation of the Azimuth-Elevation Mask.

    9. azimuth elevation mask

    Each ring represents a 10 kilometer range out to 50 kilometers. Around the edge of the view, you can see indications of North (N), South (S), East (E), and West (W). The view indicates that the view to the east, west, and south are poor. Visibility to the north is good.

Inserting the Constellation object

Load the GPS Constellation using orbital elements from GPS almanac files. The Almanac files can be stored in local directories or pulled from AGI Servers (internet connection required). STK creates a constellation that includes all of the satellites in the almanac. Keep in mind, you can build Constellation () objects yourself by loading an empty Constellation () object and assigning objects required for your analysis.

  1. Insert a Satellite () object using the Load GPS Constellation () method.

    2. Once loaded, you will see each individual Satellite () object and a Constellation () object containing all of the satellites.

  2. Open GPSConstellation's () properties ().
  3. Select the Basic - Definition page when the Properties Browser opens.

    4. You can see each GPS satellite has been moved to the Assigned Objects list. If required, you could remove any satellites from the list that are non-operational or are not required for analysis.

  4. Select the Constraints - Basic page.

    5. For the purposes of this problem, you require access to at least four GPS satellites at any given time. It doesn't matter which four. Also, take into account that when performing an access, the access will be analyzed from the satellite to the GPS tracing device.

  5. Open the 'From' access position: shortcut menu in the Logical Restriction frame.
  6. Select At Least N.
  7. Change the value to 4.
  8. Click OKto accept your changes and to close the Properties Browser.

Inserting the Chain object

A Chain object is a list of objects (either individual or grouped into constellations) in order of access.

  1. Insert a Chain () object using the Insert Default () method.
  2. Rename Chain1 () to GPStoDevice.

Defining the start and end objects

Start by choosing the start object and end object in your chain.

  1. Open GPStoDevice's () properties ().
  2. Select the Basic - Definition page when the Properties Browser opens.
  3. Click the Start Object: ellipses ().
  4. Select GPSConstellation () in the Select Object dialog box.
  5. Click OK to close the Select Object dialog box.
  6. Click the End Object: ellipses ().
  7. Select TrackingDevice () in the Select Object dialog box.
  8. Click OK to close the Select Object dialog box.

Choosing the Chain object's connections

After you choose the start and end objects in your chain, you need to build the chain's connections.

  1. Click Add in the Connections frame.
  2. Click the From Object: ellipses ().
  3. Select GPSConstellation () in the Select Object dialog box.
  4. Click OK to close the Select Object dialog box.
  5. Click the To Object: ellipses ().
  6. Select TrackingDevice () in the Select Object dialog box.
  7. Click OK to close the Select Object dialog box.
  8. Click OK to accept your changes and to close the Properties Browser.

Viewing the accesses in the 3D Graphics window

  1. Bring the 3D Graphics window to the front.
  2. Zoom To TrackingDevice ().
  3. Using your mouse, zoom out until you can see accesses from the ground site to the GPS satellites.

    4. Chain accesses

  4. Click Start () in the Animation toolbar to animate the scenario.

    5. Notice how the accesses don't appear until they're above the Az El Mask. Conversely, they disappear when they reach the Az El Mask. Terrain is being taken into account for the accesses.

  5. Click Reset () in the Animation toolbar to reset the scenario when you are finished.

Generating the Complete Chain Access report

The Complete Chain Access report shows times during which access among all objects in a chain is possible through one or more strands.

  1. Right-click on GPStoDevice () in the Object Browser.
  2. Select Report & Graph Manager... () in the shortcut menu.
  3. At the top of the Styles list clear Show Reports when the Report & Graph Manager opens.
  4. Select the Complete Chain Access () graph in the Installed Styles list.
  5. Click Generate... .

    6. The Complete Chain Access is telling you exactly what you need to know. If there is a solid line across the report, that means you always have access to at least four or more GPS satellites during the entire analytical period. If there is a break in the line, that's a period when three or less GPS satellites are being accessed.

  6. Close the Graph.

Generating the Individual Strand Access report

A Individual Strand Access report represents one possible access pathway through the chain. For a chain that consists of a series of individual objects, only a single strand is possible. If a chain contains one or more constellations, multiple strands are possible, but constellation constraints (ANY OF, ALL OF, AT LEAST N, EXACTLY N) can affect the possible number of strands.

  1. Return to the Report & Graph Manager.
  2. Select the Individual Strand Access () graph.
  3. Click Generate... .

    4. This graph shows you when the ground site can see individual GPS satellites when that satellite is paired up with at least three more satellites.

  4. Keep the graph open.

Turning off the Azimuth Elevation Mask constraint

You can verify that analytical terrain is being used in your analysis.

  1. Open TrackingDevice's () properties ().
  2. Select the Constraints - Active page.
  3. Clear the Enable check box for the Az-El Mask Constraint Name.
  4. Click Applyto accept your changes and to keep the Properties Browser open.
  5. Return to the Individual Strand Access graph.
  6. Click Refresh (F5) () in the graph toolbar.

    7. Notice how the individual strands grow larger? The surrounding terrain is no longer being used in the analysis.

  7. Return to TrackingDevice's () properties ().
  8. Select Use in the Az - El Mask frame.
  9. Click OK to accept your changes and to close the Properties Browser.
  10. Return to the Individual Strand Access graph.
  11. Click Refresh (F5) () in the graph toolbar.

    12. The individual strands shrink because analytical terrain is being used in the analysis.

Saving your work

  1. Reset () the scenario and close any reports or tools that are still open when you are finished.
  2. Save () your work.

Summary

You began by loading a USGS DEM terrain file into your scenario which you used as analytical terrain. You used the Create Color Elevation Imagery tool to create an image from the terrain data that showed elevation data colored by height in the 2D Graphics window. You used the Imagery and Terrain Converter utility to create an ISERV image which you displayed in the 3D Graphics window and the terrain converter to create a pdtt terrain file from the USGS DEM file. You used this file to visualize the terrain features in the 3D Graphics window. You inserted a Place object into the scenario that simulated a GPS tracking device. You set up the tracking device to use the terrain analytically. You propagated GPS Satellites from GPS almanac and created a Constellation object which contained the GPS Satellites. Finally, you inserted a Chain object into the scenario and created accesses from the GPS Constellation to the tracking device. You required at least four or more satellites in your analysis which you graphed using a Complete Chain Access graph and an Individual Strand Access graph.

On you own

Should you use AzEl Mask or Terrain Mask? Make sure to read the PROs and CONs between the two. When using a Facility, Place or Target object in an access computation, obscuration of the line of sight by terrain can be accounted for in one of two ways: selection of the Terrain Mask constraint or selection of the AzEl Mask constraint. While both constraints serve to model the same physical obstruction, there are important differences between the constraints which should be considered when selecting between the two. Try using Terrain Mask instead of Az-El Mask as a constraint and compare the differences in your reports or graphs and the difference in calculation time.

Also, you could enable Terrain Server and enable either Line-Of-Sight Terrain Mask or Azimuth/Elevation Mask. Place a ground site anywhere on the globe and access a satellite of your choice. Make sure to tell the ground site to use terrain. Try accessing a Ground Vehicle () object or an Aircraft () object as it moves through terrain. Have fun!