Occasionally wrong positions for AIS targets
Every now and then I see in freeboard AIS targets whose track contains erroneous positions. The track in general looks plausible, but it contains some position samples that are obviously wrong. Attached two screenshots of a case that I see right now. The track of one the vessels on a offshore anchoring location jumps to locations hundreds of miles away.
12 Replies
The above is a screenshot from the latest freeboard version. I also use a modified version, that shows tracks for a longer duration, screenshot below.
@AdrianP @Scott Bender , have you seen similar behavior? I'm not sure, if this is an issue of the vessel itself, of signalk or of freeboard.
(by the way, the new freeboard looks very good!)
In the "stock" version of Freeboard-SK tracks can either be shown using the vessel position over time or tracks fetched from the server.
Either way if there is a "jump" in the track it will be due to a position recorded against the vessel.
Are you using tracks fetched from the server (using influx plugin)?
In fb I activated the option "get trail from server" only for self, for the other vessels I do not see such an option. In the influx plugin I did not activate to write the data of others vessels to the db, only data from self is written to the db.
If the
/tracks API endpoint is available the AIS vessel tracks are sourced from there.
The option "show trails" is activated
The /tracks endpoint should be at http://IP:3000/signalk/v1/api/resources/tracks, right?
under /resources I only see this:
[
"charts",
"routes",
"waypoints",
"notes",
"regions"
]The tracks endpoint is supplied by influxdb plugin http://ip:3000/signalk/v1/api/tracks
/resources will only display resource types managed by "registered" resource providers.
For ip:3000/signalk/v1/api/tracks I see "cannot GET ..."
But since I do not write the data from other vessels to influx, I guess, it does not matter to into this for more detail
The question to me is where the "hickups" in position data comes from: AIS, sk or fb. Also yesterday and today I saw some of these outliers for (different vessels than screenshot above)
Any hint how I can debug this?
Freeboard-SK can only use and display what it receives.. it does not manipulate position e.g. default to 0,0 if position is null....
Logging the received data would allow revising the values received.
Sure, but I'm wondering if what I see is due to a bug hidden somewhere. I will think of logging, although this might be tedious since the issue appears so rarely
@Scott Bender right now I see another example of jumping positions. To log this, what plugins should I activate in order to log the relevant sk data? THE AIS data comes in via nmea2000
You can turn on Data Logging in the n2k connection to log the n2k data.