How to setup Roaming only with GPS and RTL-SDR

[smellyspice]

Hi,

I'm going to be chartering a boat soon that has no AIS equipment and wish to leverage internet/roaming reporting of my position over LTE/Mobile internet. I've done this in the past using the Boat Beacon app that reports my position (using an internet only MMSI I got a while back from Marine Traffic) -- but this time, I would like to config a Raspberry Pi, with AIS-Catcher, an RTL-SDR for receiving other vessels positions in the area and a GPS attached to the RPi's USB.

I see there is a -O <MMSI> option, but there is very little information on how to properly setup a roaming station that can report it's own position as well as those received via RTL-SDR dongle. I think I am basically looking for the feature that takes GPS in and uses AIS-catcher to generate AIS data based on local configuration and then forwards that to Marine Traffic (like Boat Beacon) and I suppose other AIS tracking sites. What is the proper way to get this setup?

FYI - I did get GPS working in the local web interface (using -N 8100 share_loc on -t gpsd localhost 2947) and I can see my own "station" on the map, but even adding the -O <MMSI> option didn't change anything locally or distribute out to other sites.

Any guidance would be greatly appreciated! Thanks

[jvde-github]

Ok, so the only thing that -O <mmsi> does is tell AIS-catcher that the receiver is on that vessel. It will use the location of that vessel as your location on the map and when generating NMEA it will use the AVDO preamble for messages from your own vessel and AIVDM otherwise.
That's all. AIS-catcher is just a simple receiver.

To share your data with aiscatcher.org, use -X followed by a sharing key you can create on the website. To share with MarineTraffic, create a station on their page and if they are ok, they will send you a IP address and PORT where you can send your data. Add to AIS-catcher command line -u IP PORT.
See also https://docs.aiscatcher.org/usage/cli/.

The alternative methods is you use the GUI and define in output where you want to send your data. Note that the -O option is not available in the GUI so it is much more limited.

Hope this helps.

[smellyspice]

Ok, I understand ais-catcher is a simple receiver -- thanks for clarifying this.

As explained above, I want to use a Raspberry Pi equipped with a GPS on board a boat, with no installed AIS transponder, to send my position (along with other locally received AIS positions received via RTL-SDR) to ais-catcher over the internet. I wrote a python script that connects to gpsd, gets positional information, then builds an appropriate AIS message to send along. This seems to be working, at least viewing the local ais-catcher web interface and also looking at the results on the aiscatcher.org website. However, although I can see my sent target, there is a discrepancy in ship details, between my local ais-catcher web interface, and the data under ship details on the hosted aiscatcher.org site.

Below are the raw nmea messages my script is outputting to the udp listener (-x 127.0.0.1 10110) of ais-catcher of Msg 18 + Msg24a/b:

!AIVDM,1,1,,A,B=Viw?@006aGQeVNA=h000040000,0*72
!AIVDM,1,1,,A,H=Viw?@LDlTpV0EQ0hu8E8000000,0*3E
!AIVDM,1,1,,A,H=Viw?D000000000000000103220,0*52

Differences between local/remote:
Status: Not available/Under way sailing
Dimensions: 11x4/ 0x0

Ship Type is blank on both, even though I have it set to type 37 (Pleasure Craft).

Note:

1. The MMSI was an internet only number I got a couple of years ago from MarineTraffic. I can't find the page where they do that anymore, so I assume they no longer offer this?
2. The GPS position is currently synthesized to put the ship on water, instead of on land where I'm coding this at the moment! :)
3. I'm using the pyais library to build the message
4. I realize the output is currently set to AIVDM instead of AIVDO (which is what it will be set to once I'm on-board with a working solution! -- but I've tested both and the results explained above are the same.

If anyone knows what might be causing these differences, I've like to know! :)

Thanks

[jvde-github]

Is that this ship? https://aiscatcher.org/ship/details/913080125

Dimension was indeed 0/0 but ran your NMEA through the process and seems to pick it up correctly. Perhaps the NMEA was not send or got lost in transmission? I see every so many seconds a message coming in (type 18) for this ship.

[smellyspice]

Indeed that is me. I can see now that the site is reporting 11 m x 4 m - which is what I'm sending. The sentences I pasted in my earlier post was the debug log out of my script moments after it started up and sent that data to the local instance of ais-catcher. Like I said, it showed up locally, but aiscatcher.org showed a report was received (the last signal field updated!), but the dimensions didn't update. I am using -X to send to aiscatcher.org. I suppose if that goes over UDP, it might have got lost and I just didn't wait the 6 mins for the next report -- although you said you saw 0/0 also, so not sure how soon after I posed you would have checked!

My script is setup to simulate a real AIS transponder for a Class B vessel with the following timers:

# Reporting Intervals (in seconds)
MOVING_INTERVAL = 30  # Msg 18
STATIONARY_INTERVAL = 180 # Msg 18
STATIC_DATA_INTERVAL = 360 # Msg 24

I also have some randomization in the logic for the static data reporting when using a simulated position to mimic GPS drift, so it doesn't report the exact same position every time.

[jvde-github]

Might be a bug then but cannot replicate or see anything in the log. I also don't see any structural issues with Class B dimensions. Will keep an eye on it.