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Positioning Application: What is the ephemeris / almanac update (upload) interval and can you change it?

  • PosApp (SimGEN / SimREPLAYplus / SimREPLAY)
  • Where applicable, default ephemeris / almanac upload intervals are specified in the satellite constellation file
  • To view the default value and/or set a new value:-
  1. In the scenario tree locate the 'constellation' required
  2. Double-click to open the corresponding 'signal sources file', e.g. [GPS constellation-->GPS signal sources file]
    1. For GPS a default of 12 hourly uploads is used and you modify this using the settings found in the [Signal control-->Upload details] page
    2. For GLONASS a default of 30 minute uploads is used for Ephemeris and 12 hourly uploads is used for Almanac. You modify this using the
          - “Ephemeris update interval” setting in the [General] page
          - settings found in the [Signal control-->Upload details] page.
                  NOTE: this control will also schedule additional Ephemeris uploads if not a multiple of the "Ephemeris update interval"
    3. For Galileo a default of 10 minute uploads is used and you modify this using the settings found in the [Uplink control] page
    4. For WAAS / EGNOS / MSAS a default of 10 minute uploads (every 2 messages, with a message rate of every 5 minutes) is used and you modify this using the
          - "GEO navigation message (9)" setting in the [Message output control] page
          - "GEO navigation update" setting in the [Signal control-->For all satellites-->General] page
    5. For IRNSS a default of 2 hourly uploads is used for ephemeris only and you modifiy this by creating your own schedule using settings found in the [Signal control-->Status control] page.
          - Almanac is only uploaded once, at the start of the scenario
  • Further details are available in the relevant section of the SimGEN user manual, DGP00686AAA.
  • For BeiDou and QZSS there is currently no equivalent, manual control of ephemeris/almanac uploads / updates.
  • Instead, the following are applied automatically 
    • BeiDou uploads occur every 1 hour
    • QZSS uploads ephemeris every 1 hour (almanac is only uploaded once, at the start of the scenario)
  • For CAPS navigation data is always read from file so the idea of uploads does not apply in this case.
    • Even if the broadcast nav data file 'describes' an upload, the simulated RF signal (satellite orbit) will not change

Product : SimREPLAYplus,SimREPLAY,SimGEN,PosApp