RSG trajectories1RSG = Real-time Scenario Generation are used primarily to simulate airborne applications, such as flight, missile or orbital trajectories. Contrary to a standard trajectories (as described under Creating a Trajectory in StudioView), an RSG trajectory is not defined by its geographic position, but by relative changes of movement.
These motion changes are captured in user-defined parameters which are assigned to SCPI commands (to learn more about SCPI commands, see SCPI Guide: Introduction). RSG trajectories are created and edited with StudioView's RSG Trajectory Editor.
About Real-time Scenario Generation
Note that RSG trajectories must be built prior to running them. However, there is also the concept of feeding trajectory data into the GSG unit in real-time, i.e. while the trajectory is being generated: This functionality requires the option kit OPT-RSG, which allows the GSG unit to receive trajectory information in real-time from e.g., a motion simulator or a computer running simulation software. For more information, see https://spectracom.com/products-services/gnss-simulation/real-time-trajectories.
Using the RSG Trajectory Editor for the First Time
- In StudioView, click in the main toolbar, the Tools menu, or in the StudioView Application Tips startup screen. The editor screen will show (the image below shows a loaded scenario for illustration purposes.)
The editor has three panels:
- The left panel shows a list of all RSG commands for the trajectory currently open (if any).
- The corresponding trajectory is visualized on the Google Map on the right.
- The charts below the m ap show speeds and altitude over time.
- Navigate to File > Open…, or click .
- Enter a Start position, and an altitude in meters. Use a semicolon and a space as separators:
- To add a new command to the list, highlight the command after which you would like to insert the new command by clicking it. Then click the button. The RSG Command Editor window will appear:
- To edit an existing command, double-click it, or click the button. To delete a command, use the button.
- To copy or move a command, you can drag & drop it using your mouse in combination with/without the CTRL key.
- To undo a command, press CTRL + Z. To redo a command, press CTRL + Y.
Note that this data actually is not part of the trajectory, it is used only to assign a relative location to the trajectory. You can later change this location, thereby moving the entire trajectory to a different place (unless the trajectory includes geographic or ECEF position change commands).
Select the command you want to use, and enter the required parameters. Detailed command descriptions can be found in the SCPI Guide.
The map and the chart on the right side of the screen will reflect any visible changes.
RSG Example: Racetrack Pattern
- Open the RSG Trajectory editor.
- Enter a Start position and altitude (m), or leave the default.
- Add VELOCITY with initial speed and heading.
- Next, add a KEEP GOING instruction in order to assign a duration to the previous command. This command will be shown with a gray background because it serves as a filler command that is not written into the trajectory file. It is used only to display the trajectory on the map, and to properly time out an action. Select a duration for the KEEP GOING filler command e.g., 5 minutes.
- Next, create a turn e.g., by 180° within 5 minutes: While this can be accomplished with the command sequence RATEHEADING, KEEP GOING, STOP, this would require some calculation to determine that the course rate change for this turn is -0.6°/s. Instead, use the Maneuver command Turn, and define the Direction change, or the radius of the turn:
- Lastly, repeat all of the steps above to complete the racetrack pattern (replace the heading with the opposite heading).
Note: With some of the other commands, the KEEP GOING command is created by StudioView (you may still need to assign a duration manually).
For the turn, select Left, Direction change: 180°, and Duration: 5 minutes.
KEPLER orbits are used to build a trajectory for space vehicles. The RSG trajectory editor's Command Editor offers a KEPLER trajectory that is – as all Keplerian orbits are – described by six parameters. These standard parameters make speed and heading change calculations unnecessary, but their specifications are beyond the scope of this documentation, and hence are not further described herein.
Note: The preferred way to describe space vehicle trajectories are TLE-formatted trajectories, see Trajectory Two-Line Element Format (TLE).
- In StudioView, navigate to the RSG Trajectory Editor.
- Click Add to open the Command Editor.
- Scroll down to Kepler orbit parameters and click OK. The parameter dialog will show:
- Populate the fields.
- Attach the Kepler trajectory to a scenario (see Configuring a Scenario). The result will look similar to the illustration below:
Note: Higher-end GSG models have a sample Kepler trajectory for the ISS pre-installed.