Dropping GPS signals

[jmdriskell 178]

I've had three instances where my GPS has lost contact with MSFS's builtin satellites, twice over the southern Indian Ocean which I attributed to possible lack of real satellite coverage (probably not) and now 600 miles out from Goose Bay on a flight from Iceland.  I'm sure that area is covered so the problem must be in MSFS and how it connects with my GPS.  Has anyone else had this problem?  Any solutions or ideas?

Thanks 

[DD_Arthur 1,068]

I’m pretty sure Working Title upgraded the satellite simulation last year based on real satellite coverage to simulate gps degradation.

I would have thought higher or lower latitudes would suffer from this exact degradation? 

What did the gps unit indicate on the satellite page? I think the units also give a visual warning when gps signal degrades past the point of being unable to maintain an accurate position.

[jmdriskell 178]

I was flying the PMDG DC-6 with the WT GPS430.  It happened the first time between New Zealand and Tasmania, the second time between Diego Garcia and Mauritius.  The last time between the southern tip of Greenland and Goose Bay.  In each case, the GPS indicated it had lost the satellites, showed 1 or 2 and was in the acquire mode.  It never synced again.  I'm sure these areas are covered in the real world and I try to keep MSFS up to date.  Maybe WT still has problems.

[hs118 707]

Sounds like a question to ask on the MSFS forums.

[MattNischan 3,782]

If you are on SU14, this bug with the WT avionics satellite simulation (it's part of the avionics and not part of the sim) gradually losing satellites is fixed in SU15.

[cianpars 1,170]

Russians hacking GPS signals again.

[jmdriskell 178]

13 hours ago, MattNischan said:

If you are on SU14, this bug with the WT avionics satellite simulation (it's part of the avionics and not part of the sim) gradually losing satellites is fixed in SU15.

Looking forward to the fix.  Sounds like the folks at WT need to go back to school so that they can provide a proper working addon.

[MattNischan 3,782]

10 minutes ago, jmdriskell said:

Sounds like the folks at WT need to go back to school so that they can provide a proper working addon.

We're the folks at WT.

The GPS simulation that exists presently in the WT avionics is one of the most advanced (if not the most advanced) GPS simulations available for a consumer flight simulator. It uses NASA orbital ephemeris data along with actual orbital mechanics solutions to place all of the real GPS satellites currently in orbit into their real 3D positions in space at the current time, and correlates those locations into an actual sight picture for the GPS receiver of the currently viewable satellite constellation. GPS signal strength based on angular horizon distance is simulated and each satellite is tracked separately by the receiver up to the number of available receiver channels.

In addition, the system is loaded with the geostationary positions of the regional SBAS satellites (WAAS, EGNOS, GAGAN, and MSAS) as well as the coverage areas of the ground portions of those systems. As such, it also computes your SBAS availability based on the geostationary SBAS constellation that may be visible from your ground location and your ground service coverage area. All of these satellites are represented within the system and on any relevant displays with their real world satellite IDs. Additional simulated features include individually tracked satellite solution time, system solution figures of merit (vertical and horizontal), almanac downloads, and system solution status.

As can happen in systems of this complexity, occasionally a bug or two can arise. In SU14, there is a bug where satellites are not re-acquired over long time ranges and can be forgotten or failed to be rediscovered by the receiver. This only affects longer flights, generally, and is fixed in SU15.

-Matt

[jmdriskell 178]

Thanks for the very detailed explanation of how the system works and for sending ME to school.  I've been generally satisfied with WT's GPS430 representation in the PMDG DC-6 and find it works as advertised in most occasions.  I'm looking forward to the implementation of SU15 when hopefully the satellite dropping problem will be gone.

Back in the early days when Icelandic Air was flying DC-6s on the same route as I was simulating yesterday, they didn't have to worry about GPS satellites dropping.  They used tried and true navigation skills to get from point a to b.  I like to keep these skills alive as I was taught when I got my license in the early 1970s.

Again, thanks for the clear explanation.

Jim Driskell