Over the Horizon AIS compatibility
Over the Horizon AIS (OHA) streams AIS data from the DataHub in standard NMEA2000 and NMEA0183 format. Any compatible chartplotter or navigation app can receive and display these targets.
The number of targets your device displays depends on its own limits, not OHA's. Test your setup and adjust OHA's range and target age settings to match what your device can handle.
Over the Horizon AIS was developed and tested initially on RayMarine Axiom chart plotters and with AquaMaps on a laptop; however, we have also received reports that it works well on many other RayMarine, B&G, Simrad, Furuno and Vesper devices. If you enable Over the Horizon AIS and find an unlisted brand that works for you, please let us know so we can update this article.
Device / App-specific compatibility feedback
From our testing, and with thanks to customers who have shared with us their feedback with us about Over the Horizon AIS on their devices, please note the following:
Garmin devices have been reported as displaying targets up to 75 miles only.
Some Garmin-brand Chartplotters are incompatible with Over the Horizon AIS. They require NMEA2000 data in a proprietary Garmin format that is unavailable to PredictWind. If your Garmin does work, please let us know. Your Garmin GPS will work fine for GPS tracking; this may only affect the AIS display.
Furuno and Raymarine Axiom devices display up to the closest 100 AIS targets from all sources. Chartplotters have a limited CPU capacity, and their software is designed to prioritize and track the nearest targets to avoid collisions, so this is expected.
Some RayMarine devices will require a DataHub Firmware update to display target names correctly.
The Navionics App displays up to the closest 100 AIS targets from all sources.
Open CPN and Time Zero have been reported to work with Over the Horizon AIS. Time Zero may not show vessel dimensions.
Is Over the Horizon AIS a replacement for VHF AIS?
No. OHA complements your existing VHF AIS — it does not replace it. It acts as a reliable backup if your VHF AIS receiver fails, so you're never without collision avoidance or navigational safety.
OHA extends your AIS range by up to 300 nautical miles beyond standard VHF reach.
Over the Horizon AIS Setup
I cannot see Over the Horizon AIS to enable it on the DataHub
If you cannot see the option to enable Over the Horizon AIS in the DataHub, please check your Firmware is version 4.08 or later and your PredictWind Account details have been validated in the DataHub.
To validate your PredictWind Forecast Account in the DataHub:
Click the Settings->Settings menu, then click the top menu Account.
Type in your PredictWind Professional subscription email address and password.
Click Save & Apply.
If successful, you will see Status: PROFESSIONAL appear.
My PredictWind Account settings fail to validate. Status: INVALID
If your email address or password needs to be corrected from above, it will show Status: INVALID. Please check that they are both correct, using the * to reveal the password.
Why can't I use Over the Horizon AIS on the DataHub?
To see and use Over the Horizon AIS on the DataHub, you need the following:
A PredictWind Forecast Professional subscription. You can upgrade to Pro here.
DataHub Firmware version 4.08 or later.
Your PredictWind Forecast Account is validated in the DataHub.
Over the Horizon AIS is enabled in the DataHub.
An available Internet connection for the DataHub via Starlink, 4/5G LTE cellular or Iridium GO exec. Note: The original Iridium GO is not supported — only the Iridium GO exec works with OHA.
To view Over the Horizon AIS requires a Chartplotter connected via NMEA2000 or Wi-Fi, which can display AIS supplied in a standard NMEA0183 or NMEA2000 format. You can also view AIS data in navigation software Apps on a device connected to the DataHub via Wi-Fi if configured to receive the DataHub AIS feed, e.g. AquaMaps, OpenCPN or Navionics on a laptop or iPad. We expect Expedition to work; please let us know.
Over the Horizon AIS Usage
How often does Over the Horizon update?
Sampling intervals are up to 1 minute for direct, always on high-speed Internet, e.g. Starlink, Wi-Fi hotspot, 4G/5G router or cellular USB tethering. Update frequency is reduced where many targets are acquired to prevent overwhelming the N2K network.
Where the Iridium GO option is enabled, the DataHub will update AIS through your Iridium GO exec each time it polls, e.g. 60 minutes or as frequently as 15 minutes.
⚠️ The original Iridium GO is not supported. OHA only works via the Iridium GO exec.
Is Over the Horizon AIS data included in my GO exec PredictWind Plan?
Yes! This data is included in your GO exec Unlimited PredictWind Data plan.
Over the Horizon AIS data is also excluded from your daily weather forecast download limit, up to 1.5MB per weather download and 12 MB per day. Please note: if you activate AnyApp data, all data transferred during that session will be deducted from your AnyApp data balance.
Is Over the Horizon AIS data included in my GO exec MB monthly airtime plan?
This data is treated like any other data the GO exec transfers for other monthly plans. This is another excellent reason to switch to the Unlimited Plan if you've not already.
For other GO exec MB plan customers, after activating Over the Horizon AIS, please monitor your data usage via the GO exec data counter and your Satellite account to ensure you do not incur unexpected overages.
How much data does Over the Horizon AIS use?
Data usage depends on your range, target age, and update frequency. The figures below give a general guide:
Scenario | Estimated data usage |
1,000 vessels, updated hourly | ~307 KB/day |
5,000 vessels via GO exec, 15-min polling | ~64 KB per update (~6.14 MB/day) |
Can I limit Over the Horizon AIS data usage to a fixed amount?
A specific data limit cannot be set directly for Over the Horizon AIS. To reduce the amount of data transferred, please reduce the Range and Target Age, and if via Iridium GO exec, adjust the Polling Interval in the Tracking menu.
Can I stop Over the Horizon AIS using my GO exec?
Yes! Please remove the tick from the Iridium GO box and click Save & Apply.
How can I tell DataHub AIS vs VHF AIS targets?
The DataHub automatically tags AIS targets sent via NMEA2000 as being acquired from the DataHub. If you tap to view more AIS target information, this should be displayed on your Chartplotter or Navigation App.
For apps that don't support NMEA0183 tags, enable the Mark AIS setting. This sets the Callsign field in AIS sentences to "DATAHUB", making it easy to tell DataHub targets apart from VHF targets.
Class A ETA and destination are also modified to display the time of the last position update.
Can I see a demo of Over the Horizon AIS?
Sure! This video by Luis Soltero, the DataHub designer and developer, demonstrates Over the Horizon AIS and explains how it works.