Working with Multitrack Objects

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.

Capabilities covered

This lesson covers the following STK Capabilities:

  • STK Pro

What you will learn

This tutorial is an introduction to the Multitrack object (MTO) in STK. In this exercise, you will:

  • Create an MTO Object
  • Change the appearance of MTO tracks in the 2D Graphics window
  • Modify the view of an MTO in the 3D Graphics window

You can use MTO objects within STK to group together many moving or stationary objects. An MTO consists of one or more "tracks." Each track consists of points with time, latitude, longitude, and altitude information.

MTOs are the most efficient way to quickly display a large number of objects within STK. However, MTOs are only for visualization. If you want to perform analyses such as graphs, reports, and access calculations with your objects, you cannot use an MTO object.

For this tutorial, you will create and visualize four paths: a friendly ship, a friendly ground vehicle, an enemy ship, and an enemy ground vehicle.

Creating a new scenario

  1. Launch STK ().
  2. Click Create a Scenario in the Welcome to STK dialog box.
  3. Enter the following in the New Scenario Wizard:
    OptionValue
    NameMTO_Scenario
    LocationDefault
    Start1 Aug 2015 15:00:00.00
    Stop+ 1 day
  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.

Changing the date format

For this scenario, change the date format to epoch seconds.

  1. Right-click your scenario, MTO_Scenario ().
  2. Open MTO_Scenario's Properties ().
  3. Go to the Basic - Units page.
  4. Change the DateFormat to Epoch Seconds (EpSec).
  5. Click OK to save your changes and close the MTO_Scenario properties browser.

Creating an MTO object

Insert an MTO object into the scenario.

  1. Click Insert Object (), located in the Default toolbar.
  2. Click Edit Preferences....
  3. Select the check box next to MTO and click OK.
  4. Select the MTO object () and Define Properties method. The MTO object's properties browser appears.

Adding tracks

Add four tracks to the MTO object. Each track represents one vehicle.

  1. Go to the Basic - Tracks properties page. This page displays all tracks that are part of the MTO.
  2. Click New four times to add four tracks to this MTO object.
  3. Highlight the first track and click Modify.... The "Modify Track Data" dialog box appears.
  4. Name this track "Friendly Ship".
  5. Click Insert Point.
  6. Double-click each field of the first point to enter the following data:
    7. Option Value
    Time 0 EpSec
    Latitude 42.4 deg
    Longitude -86.6 deg
    Altitude 0 km
  7. Click Insert Point again and modify the second point with the following data:
    8. Option Value
    Time 10000 EpSec
    Latitude 43.1 deg
    Longitude -86.5 deg
    Altitude 0 km
  8. Select the Interpolate Position check box to make sure that the track computes intermediate points from one point to the next as you animate.
  9. Click OK to close the "Modify Track Data" dialog box.
  10. Click Apply in the MTO properties browser.

Viewing the Friendly Ship track

Take a look at the track of the Friendly Ship.

  1. In the 2D Graphics window, zoom in on the Great Lakes area. Alternatively, you can zoom in on a rectangle roughly centering on 42 degrees latitude, -86 degrees longitude.
  2. Animate the scenario. You should see a marker representing your "Friendly Ship" track move along the east side of Lake Michigan.

Modifying the other three MTO tracks

Return to the Basic - Tracks page of your MTO object properties browser. Modify the other three tracks according to the table below, making sure that you select the Interpolate Position check box for each track.

STK will automatically rearrange the points by time, so after entering the data for point #2, it may jump to the #3 position.

Track Name Point Time Latitude Longitude Altitude
2 Enemy Ship 1 0.0 42.7 -87.6 0
2 6000.0 43.4 -87.0 0
3 10000.0 43.3 -86.5 0
3 FriendlyTruck 1 0.0 40.8 -84.4 0
2 5000.0 41.2 -85.0 0
3 10000.0 41.8 -85.3 0
4 EnemyTruck 1 0.0 43.2 -86.1 0
2 7000.0 42.2 -85.7 0
3 10000.0 42.1 -85.0 0

After inserting all of the track points, click OK on MTO object properties browser and animate the scenario. You should now see all four of your objects move along the MTO paths.

Adjusting graphics attributes

In this section you will adjust certain attributes to make the MTO graphics easier to see and understand.

Changing the line width

Make your track lines thicker by adjusting a 2D Graphics attribute.

  1. Open the properties browser of the MTO object again.
  2. Go to the 2D Graphics – Track Attributes page.
  3. Click Select All.
  4. Click Modify. This opens the "Modify Track Graphics Data" dialog box.
  5. Change the Line Width value to 3.
  6. Click OK to save your changes and close the dialog box.
  7. Click Apply On the 2D Graphics – Track Attributes page, you should see that the paths displayed are now thicker.

Changing marker styles

To make it easier to identify the types of objects represented, you will now change the markers for the paths.

  1. Go back to the 2D Graphics – Track Attributes page
  2. Highlight the first path and hold down the Ctrl key while clicking on the second path to multiselect the two ships.
  3. Click Modify. This opens the "Modify Track Graphics Data" dialog box.
  4. Change the marker style to the ship icon
  5. Click OK to save your changes and close the dialog box.
  6. Multiselect tracks 3 and 4.
  7. Change their marker style as you did in steps 3-5 but using the ground vehicle icon.

Changing colors

You can use color to distinguish between "friendly” and “enemy” vehicles.

  1. Multiselect tracks 2 and 4.
  2. Click Modify. This opens the "Modify Track Graphics Data" dialog box.
  3. Using the drop-down selection, change Color to red.
  4. Click OK to save your changes and close the dialog box.
  5. Use the same procedure to set tracks 1 and 3 to green.
  6. Click Apply in the MTO object properties browser.
  7. Animate the scenario. You should now see two ship icons and two ground vehicles. The red paths represent enemy vehicles and the green paths represent friendly vehicles.

2D View of the MTO paths

Applying 3D models to the MTO objects

You can replace the object markers with models of the ships and ground vehicles.

  1. Open the 3D Graphics – 3D Track Attributes page in the MTO object properties browser.
  2. Highlight track 1 and click Modify. This opens the "Modify Track 3D Graphics Data" dialog box.
  3. Select the Show check box in the Model area.
  4. Click the ellipsis () button next to Model File.
  5. Select the file ship.glb in the Sea directory.
  6. Set the log scale to 2.0.
  7. Clear the "Z Points toward Nadir" check box.
  8. Click OK to save changes and close the "Modify Track 3D Graphics Data" dialog box..
  9. Repeat the above procedure to make the following settings for the other tracks:
    10. Track Model File Log Scale Z Points Toward Nadir
    2 Sea\aegis-destroyer.mdl 2.3 No
    3 Land\military-truck.mdl 3.5 No
    4 Land\humvee.mdl 3.5 No
  10. Click Apply in the MTO object properties browser and animate the scenario. The 3D Graphics window now shows models for the objects as they travel along the MTO tracks.

Setting the view to an MTO path

You can set your view to one of the MTO paths.

  1. Go to the Basic – Tracks page.
  2. Set the Computation Track Id to 3.
  3. Click OK to save your changes and close the MTO object properties browser.
  4. Click the View From/To () button on the 3D Graphics window toolbar.
  5. Select the MTO object in the View From field.
  6. Click OK. The view will now be centered on the friendly truck, which is track number 3. By changing the Computation Track Id, you can change which path the view will be centered on when selecting the MTO as the View From/To object.

Saving your work

Make sure to save your scenario before exiting STK.

Summary

This tutorial provided an introduction to Multitrack Objects in STK. Although you cannot use them for numerical analysis, MTOs provide a way to efficiently display the positions of hundreds or thousands of objects in STK.

The MTO paths in this activity were defined with the graphical user interface. However, you can also modify MTO positions and properties through automated processes interacting with STK.