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Old 13-04-2014, 10:20   #1
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Flight Simulator as GPS test NMEA genarator

Want to add a new dimension to testing? Tracks generation and chart shifting combined with 3D view of the coastline... try FlightGear - an Open Source Flight Simulator. It seems hard to fly slower then 40 kts, otherwise lots of fun. Outputs NMEA to UDP port 5500 (default).
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Old 09-05-2014, 02:44   #2
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Re: Flight Simulator as GPS test NMEA genarator

While playing with FlightGear I put together a tool that might be also useful elsewhere... it is a Python program to convert a stream of $GPRMC sentences to a stream of corresponding !AIVDM sentences (with some assumptions). It supports AIVDM Type 1 (Class A Position Report) and Type 9 (SAR Aircraft). UDP in and out. Source attached.
It should not be too difficult to add more sentences, as needed.
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Old 09-05-2014, 12:43   #3
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Re: Flight Simulator as GPS test NMEA genarator

Is the 3D coastline view of just the USA? Or the whole world?




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Old 09-05-2014, 18:56   #4
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Re: Flight Simulator as GPS test NMEA genarator

We should add support for topographical data to opencpn...
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Old 10-05-2014, 01:52   #5
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Re: Flight Simulator as GPS test NMEA genarator

Quote:
Originally Posted by MarkJ View Post
Is the 3D coastline view of just the USA? Or the whole world?
FlightGear bulds the scenery from TerraServer data. It covers the whole world, coming in 1x1 degree tiles, except for all-water parts of the globe.

There is an associated charting application, Atlas (Open Source), that builds square .png chartlets from this data in any resolution desired, also 1x1 degree tiles.

I converted some of these tiles to .KAP charts using img2kap, so they are usable with OCPN. With some script-writing effort all of these tiles could be converted to .KAP for the whole world... but: 1x1 is impractically small and as OCPN does support only cylindrical projections (I think) it would not be useful in high latitudes. One can stitch together small tiles into bigger ones, but implementing Lambert conformal conical projection may be not worthwhile for a marine chartplotter (but SeaClear II does it!).

The waypoints marking airfields are in a layer taken from a database of aviation waypoints, distributed in GPX format, slightly massaged...

Google "FlightGear Scenery download" shows it all...
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Old 18-05-2014, 07:11   #6
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Re: Flight Simulator as GPS test NMEA genarator

Nothing conclusive, but just some food for thought re: SAR Aircraft - alarm/acknowledge policy, etc.

- An aircraft (usually) behaves differently from a ship, so some alert actions may be not quite appropriate or meaningful...

- According to ITU-R M.1371-4 AIVDM Type 9 should be transmitted by default every 10 secs, but it can be every 2 secs, "if during a SAR mission"... It would be interesting to know if there is actually a mission underway, but I did not find any indication of this in any message data.

- The specs also state that a SAR Aircraft can transmit static data via Type 5 or Type 24 A/B message, giving the call-sign, name/registration number, possibly dimensions, ETA, destination etc. as well.

- The MMSI includes a hint if the plane is a fixed-wing type (111MID1xx) or a helicopter (111MID5xx)

- An aside: OCPN is quite tolerant on NMEA format: spurious commas and lower case for checksum encoding ("0*2a" vs. "0*2A") is accepted, while some more strict decoders reject these sentences. I sometimes forget this and spend time again digging into the checksum algorithm... :-(

PS.

I use a very historic version of FlightGear for its operational simplicity and light footprint, but the modern versions feature truly amazing graphics...

A new version of Python UDP Connector is attached. It shows altitude from $GPGGA and includes some new capabilities.
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Old 08-06-2014, 10:26   #7
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Re: Flight Simulator as GPS test NMEA genarator

New version of Python AIS encoding toolkit attached. Can encode also static data for Type 5 sentences from a csv database and send output to serial and UDP ports.

First example shows the "Vinson_demo" scenario on a NOAA raster marine chart. DELL and TOSHIBA targets come from two separate multiplayer computers.

Second example (2 pictures) shows a view of "Vinson_parade" scenario on a NOAA Tactical Pilotage Chart (Lambert Conformal Conic projection) with SeaClear II software.

Third example shows the "Vinson_parade" with 2 multiplayer planes on a marine ENC chart.

The last example shows that a naive conversion of Atlas tiles to Mercator charts fits reasonably well even in Alaska (latitude 60 N). Also some use of routes...

Pity that OCPN does not handle static data (names, call signs) for SAR aircraft in the AIS Target List ...
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Old 03-07-2014, 10:35   #8
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Re: Flight Simulator as GPS test NMEA genarator



I took the AIS transcript of the Round the Island Race 2011, showing lots of targets... and converted it to a FlightGear scenario.. some 300 boats there.

Some simplifications: all yachts look the same, they assume positions, cog and sog of the first occurrence in the stream, so some collisions and sailing over land, but overall the 3D picture is more relaxing than AIS view on chart.

I honestly did think this will break the simulator... kudos to the team!
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