FA-70 "PA Low"

[Elorent]

Setting up a new unit and it is showing in the AIS Setting Tool and broadcasting in the position report "Position Accuracy: Low". It has 11-12 satellites in view and is in 3D mode.
I also tried a different gps antenna with the same results and satellite count and 3D status. Has anyone else seen this? I'm wondering if after mfd install, a firmware update through the mfd is available? I don't see any update tool in the AIS Setting Tool program.

 

[Johnny Electron]

Do you have an error light on the box? Otherwise it likely isn't anything to be concerned about. What has caused the concern?
In AIS terminology, Position Accuracy is a binary flag (either High or Low):

• High: Means the position error is estimated to be less than 10 meters. This usually requires a DGPS (Differential GPS) correction or a very strong SBAS (like WAAS) signal. (Not being a primary GPS system AIS units typically don't offer these additional fix methods)
• Low: Means the position error is greater than 10 meters.
  
  Looking at your screenshot, several factors provide context:
  
  • Status: 3D: You have a solid 3D fix, which is good.
  • Satellites in View: 11: This is a healthy number of satellites.
  • RAIM: Used: Receiver Autonomous Integrity Monitoring is active, which means the unit is cross-checking satellite signals for errors.
    
    
    Even with 11 satellites, if the unit isn't receiving a specific differential correction signal to pull that accuracy under the 10-meter threshold, it will default to Low. For most maritime navigation and AIS reporting, a "Low" status (standard GPS accuracy) is perfectly normal and acceptable.

 

[Elorent]

Do you have an error light on the box? Otherwise it likely isn't anything to be concerned about. What has caused the concern?
In AIS terminology, Position Accuracy is a binary flag (either High or Low):

• High: Means the position error is estimated to be less than 10 meters. This usually requires a DGPS (Differential GPS) correction or a very strong SBAS (like WAAS) signal. (Not being a primary GPS system AIS units typically don't offer these additional fix methods)
• Low: Means the position error is greater than 10 meters.
  
  Looking at your screenshot, several factors provide context:
  • Status: 3D: You have a solid 3D fix, which is good.
  • Satellites in View: 11: This is a healthy number of satellites.
  • RAIM: Used: Receiver Autonomous Integrity Monitoring is active, which means the unit is cross-checking satellite signals for errors.
    
    
    Even with 11 satellites, if the unit isn't receiving a specific differential correction signal to pull that accuracy under the 10-meter threshold, it will default to Low. For most maritime navigation and AIS reporting, a "Low" status (standard GPS accuracy) is perfectly normal and acceptable.

Thank you for the explanation, it makes perfect sense. I didn't know the threshold was at 10 meters. I've only seen this on Garmin units and Garmin tech support could not answer or explain it to me. Navico and Raymarine have always shown accuracy: high, so maybe they are utilizing waas. My concern was that the low position accuracy message is being broadcast to other boats in the ais position/status report. I know the position is good, but for collision avoidance, the other vessel may wonder if the position is accurate. Again, thank you for the precise explanation that I can relay to my clients as well as ease my concerns.
Cheers,
Eric

 

[Johnny Electron]

Talking to our repair center the "3D" fix shows that your unit is picking up WAAS so the fix you have is actually even better than I was thinking. The High is less than 1 meter in this case. To see high reflected they said you would need to send over something much higher like a GPS that has high precision DGPS like a high end commercial GPS unit. Anyway, your example unit is working very much like all that we see so unless you have some other indications of an issue, there likely isn't any.