Creating a Scenario

This procedure guides you through the settings to create a scenario using the Scenario Generator node on the software's user interface (UI). To learn more about individual cell settings, refer to the UI descriptions.

Scenario Generator Settings Figure:

1. Click Scenario Generator in the tree view.

   Notice that the Generation Mode is set to Create, which is the default setting.

2. Click Comment and add text if there is a need to add a comment to the scenario.

   The comment entered here also appears if the scenario is modified with the Edit selection of the Generation Mode property.

3. Set the Elevation Mask Angle

   The software sets the mask from the horizon to the angle entered. This means that the software only recognizes satellites that appear above the mask value.

4. If desired, set the Troposphere Model to NATO or leave as No Model.

   Some tests, such as in the 3GPP standards, require the NATO model selection.

5. Select the Ionosphere Model: Klobuchar or No Model.

6. If Klobuchar is the Ionosphere Model, set the parameters for the Ionosphere Parameters cell that appears after making the Klobuchar selection:

   1. Click on the + sign displayed to the left of the Ionosphere Parameters cell to display the Alpha [0–3] and Beta [0–3] cells.

   2. Set the Alpha and Beta parameters.

      If a particular test from the 3GPP standards includes these values, set the Alpha and Beta cell values to match the 3GPP test values.

7. Configure the Scenario Type settings for either Static or Dynamic (moving GNSS receiver).

   If you select Dynamic, the software removes some settings (cells) that are requirements only for the Static selection.

   Static Type Settings:

   1. Set the Initial Longitude.

   2. Set the Initial Latitude.

   3. Set the Initial Altitude.

   4. Set the Duration (HH:mm:ss) with the length of time that the scenario plays back. 24 hours is the maximum time period.

   Dynamic Type Settings:

   1. Click the NMEA Message File cell, and use the dialog box button to launch the Open File dialog box for navigating to and selecting the NMEA message file.

      The software accepts NMEA message files that contain both the GGA and RMC messages. The GGA message is mandatory and contains the time, but the RMC, which provides the date, is optional. The software sets the Start Date and Start Time (GPS Time) cell based on these messages. If there are multiple messages, the software uses the date and time from the first RMC and GGA message it encounters as the scenario start date and time.

      If desired, you can override the software's date and time entries from the RMC and GGA messages. Just select the cells and enter your own date and/or time values.

   2. If the NMEA message file does not contain the date, set the Start Date cell with the start date of the scenario simulation.

8. Set the Start Date of the scenario simulation. While the software automatically sets the start date, if there is a need, user input is allowed to overwrite these values:

   • For static scenarios, the start date is automatically updated by TOA (Time of Applicability) information in the selected almanac files.

   • For dynamic scenarios, the software always uses the start date from the NMEA message, which is determined by the first RMC message in the NMEA message file. However, user input is allowed if there is a need to overwrite these values. If the RMC messages are not included in the NMEA message file, the scenario uses the TOA from the selected almanac. The user may want to manually change the date to the one that they want to simulate.

   • Set the date by either manually entering the date, or by clicking the cell and using the dialog box button to launch the Date Time Editor. By using the editor, you can set both the Start Date and Start Time (GPS Time) values. The start date and time must be later than 1980-01-06 00:00:00. It is recommended to use a start time on a 6 second boundary, because GPS time-of-week is counted in units of 6 seconds.

9. Set the Start Time (GPS Time) of the scenario simulation. While the software automatically sets the start time, if there is a need, user input is allowed to overwrite these values:

   • For static scenarios, Start time is automatically updated by TOA information in the selected almanac files.

   • For dynamic scenarios, the start time is determined by the first GGA message in the NMEA message file. However, user input is allowed if there is a need to overwrite these values.

   • Set the time by either manually entering the time, or by clicking the cell and using the dialog box button to launch the Date Time Editor. By using the editor, you can set both the Start Date and Start Time (GPS Time) values. The start date and time must be later than 1980-01-06 00:00:00. It is recommended to use a start time on a 6 second boundary, because GPS time-of-week is counted in units of 6 seconds.

10. Set the constellation type settings (GPS Settings, GLONASS Settings, etc.):

    1. For each constellation required to be in the scenario, set their Enabled property to Onotherwise set it to Off.

    2. For all constellations with Enabled set to On, set their remaining properties.

       Refer either to hints embedded in the software UI, or use the Scenario Generator UI descriptions, which may have more information than the hints such as URLs to almanac files and special considerations.

11. Set the Leap Seconds Mode.

    You can choose either Official (defined by IERS) or User.

    Selecting User provides the additional cell User Leap Second that gives you access to the Leap Seconds Editor where you can create your own leap seconds configuration.

12. Set the Antenna Pattern Settings:

    1. Set the Antenna Pattern cell to either On or Off.

       If set to On, the software configures a gain mask and adds three additional cells covered in the remaining substeps:

       

    2. If desired, change the values for the Elevation Resolution, Azimuth Resolution, and Azimuth Rotation cells by clicking the cell and entering a value. 

       The values in these cells affect the Antenna Pattern display shown in the Antenna Pattern node.

       

    3. Select the Antenna Pattern node.

    4. Configure the Antenna Pattern gain mask.

    5. Select the Scenario Generator node.

13. Click the Create Scenario button to launch the Save As dialog box for selecting a location and saving the file.

    After creating the scenario, click on the Scenario Graphics node to view the satellites used during the time of the scenario for each channel.

Related Topics

Scenario Generator

Scenario Graphics

Antenna Pattern