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FG with Marine Chartplotters

Atlas is an addon that lets FlightGear users display a real-time "moving-map" of their flight.

FG with Marine Chartplotters

Postby metoo » Sun Jun 08, 2014 6:48 pm

Atlas is very nice, but - since many of the scenarios involve naval operations - it would be quite natural to view these on a real marine chartplotter, showing ships and aircraft as AIS targets on real marine charts...

I prepared some tools to output and convert FG data stream into AIS sentences. This should work with any AIS-enabled software, but I looked mostly at freely available tools, namely OpenCPN and SeaClear II.

Open Chart Plotter-Navigator (open source, reads directly UDP and serial inputs.
SeaClear II (also free, but closed source, reads serial inputs.

Both programs offer full capabilities for viewing AIS targets, measuring distances, setting waypoints, planning routes, managing tracks and handling multiple chart formats and sources.

OpenCPN allows the user to supply own icons and to customize the appearance of routes and tracks.

SeaClear II has the advantage of handling charts in Lambert Conformal Conic projection, so e.g. the NOAA Tactical Pilotage Charts can be used, when calibrated with included MapCal II application.

The Atlas-generated tile images can also be prepared as Mercator charts for use with both programs.

All this works very nice, with some limitations and problems specific to FG.

- AIS understands only ships and "SAR aircraft", not "general aircraft", so limits altitude shown to 4094 m
- the "own ship" concept in the plotters is always a ship, so no altitude data is normally provided
- AIS expects ships and aircraft to send position messages at most every 2-5 seconds, while FG seems to handle output protocols at minimum 1 Hz
- FG AI craft are not always properly identified, while AIS requires unique identification for every vessel
- the standard icons are not always well visible on topographic charts, since they were designed to fit a clear (sea) background

The chartplotters can also read Atlas stream directly and interpret it as "own ship" position data, with the limitations as above.

What is the use of this?

1. The marine chartplotters are readily available, powerful tools with rich functionality
2. The FG scenarios can provide "live" data for complex testing and learning
3. Using the practical chartplotting tools brings the experience even closer to reality

This is just a simple test, a proper implementation of AIS output would probably require some Nasal scripting and maybe core development to implement AIVDM protocol in a similar way to how Atlas protocol is implemented ...

The tools and some screenshots are available at the OpenCPN forum: ... ost1543768

See last post for newest toolkit. This includes Python scripts and some data. The zip archive ".doc" extension should be stripped before unzipping.

- converts Atlas stream of RMC/GGA sentences into AIVDM
- converts data output with a special protocol "aivdm" into AIVDM
- aivdm.xml is a simple FG protocol definition, sending out data about 3 carriers, 9 escorts, 9 ships, and 9 AI aircraft
- vessels.dat contains static data about vessels used in most of FG scenarios
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Re: FG with Marine Chartplotters

Postby yanes » Sun Sep 07, 2014 8:53 pm

I currently use opencpn with my FG3.0 It works fine with UDP stream coming from FG 3.0 This was tested under WIN7 and linux (Ubuntu 14.04)
it works as smooth as it should , All my routes LOC tracks and glideslope wpts are saved there ,

OpenCPN 3 Scrshot for OMDB approach
KSFO and near airports
The last one is screen shot with MaxSea which is a proprietary (Windows only) program .
I recommand it for VFR Flight
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Re: FG with Marine Chartplotters

Postby tetramonium » Tue Jan 05, 2016 4:48 pm

Thank you for your work
I use at2vdm to convert $GPRMC to see radiosondes from Sondemonitor in Opencpn.
Some times at2vdm seem stop
I'm not familiar with python but I understood why
I changed the line
g_sec = int(tt%100 + ((tt/100)%100)*60 + ((tt/10000)%100)*3600)
g_sec = int(str(tt)[0:2])*3600+int(str(tt)[2:4])*60+int(str(tt)[4:6])
Probably not beautiful, but work
Sorry for my bad english
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Re: FG with Marine Chartplotters

Postby Hooray » Tue Jan 05, 2016 7:12 pm

I like the idea very much, if you are able to build from source and know a little C++, we could probably walk you through the necessary changes.

From an interfacing standpoint, there are already several modules that are using NMEA internally

Apart from that, there's also Torsten's Phi work, and TheTom's Canvas system that could be used within FlightGear to create/provide integrated plotting capabilities.
Please don't send support requests by PM, instead post your questions on the forum so that all users can contribute and benefit
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