Settings / AIS and NMEA
NMEA and AIS
NMEA is a marine industry standard for communicating information between on-board devices. Automatic Identification System (AIS) is a standard for exchanging vessel location and other information using VHF radio signals. AIS data is typically shared between on-board devices using NMEA.
SEAiq supports using external NMEA/AIS information over WiFi and (for devices that support it) Bluetooth. SEAiq can also be configured to act as an NMEA server, forwarding own its information to other devices.
With the appropriate configuration settings in SEAiq you can do the following:
- Display AIS targets on the Navigation tab and access information about vessels reporting AIS information under the AIS tab.
- Use your vessel's onboard GPS in place of your device's internal GPS.
- Access and display numerous sensors from your on-board systems.
- Use GPS on devices that do not include integrated GPS.
- Forward GPS from one device to another (when you have several devices and some do not have GPS hardware).
AIS uses NMEA to communicate its data, so you will need to configure NMEA in order to use AIS.
Numerous alarms are provided for NMEA data. Among these include an alarm to indicate data corruption. When at least 5% and 10 "sentences" in the prior 5 minutes have checksum errors, an alarm will be presented. These are shown at most once per 5 minutes.
This section describes how to connect your device to an NMEA data feed over WiFi. Before adjusting these settings, you first ensure your NMEA data feed and this device are connected to the same network.
- Enable: This switch turns on NMEA support. Normally, you should enable this only after first setting the other configuration items.
- Inactivity Alarm: When enabled, an alarm is generated after 15 seconds of inactivity during which no NMEA data was received. After pressing OK, the alarm is disabled for 60 seconds. If no data has still been received, it fires again.
- Inactivity Alarm Reminder: When enabled, a warning is generated when (1) data is received from NMEA and (2) the Inactivity Alarm is disabled. A warning is given asking if you would like to enable the Inactivity Alarm. Pressing Alarm, enables the inactivity alarm. Pressing OK disables this warning for 5 minutes, after which it may fire again.
This also functions similarly for Extra NMEA Connection, if that is enabled.
- AIS Alarm: When enabled, alarms reported from AIS are shown. Alarms cause the display to flash with a warning message. After dismissing the alarm, no further AIS alarms are reported for at least 2 minutes.
Regardless of whether alarms are enabled, recent alarms from AIS can be viewed under Settings / NMEA and AIS / Diagnostics.
- HDOP Alarm: (Only SEAiq Pilot) When enabled, an alarm is generated if GPS HDOP exceeds 5.0. HDOP is an abbreviation for Horizontal Dilution of Precision, an estimation of the accuracy of GPS positions. If an alarm occurs, it is disabled for 60 seconds after you acknowledge it.
This alarm requires that an HDOP value is received from NMEA/AIS. Typically, this information is not available from a basic WiFi AIS Pilot Plug. If no HDOP is received, no alarm fires.
- Own-Ship Data Alarm: When enabled, an alarm is generated when the data source for Own-Ship GPS, COG, SOG, HDG, or ROT is lost or changes in a way likely to reduce data quality. Also, a listing of the source of these sensor data is shown in the Source panel of the status bar.
- Show Device GPS: (Only SEAiq Pilot) When enabled, the device's internal GPS position is displayed along with position from NMEA/AIS. A circle marked INT indicating the radius of Horizontal Position Error is also shown. The position is intended to be used to help validate GPS information reported from NMEA/AIS.
If other GPS positions are available but were not used for display of Own-Ship, they are also shown. Possible other positions include AIS, NMEA (for Primary NMEA), and EXTRA (for Extra NMEA).
- NMEA Verification Alarm: (Only SEAiq Pilot) When enabled, an alarm fires if NMEA/AIS and GPS position differ by at least 100m. After acknowledging an alarm, it is disabled for 60 seconds.
The alarm incorporates the relative positions of the NMEA and GPS antennas in determining the alarm distance. See Own-Ship settings.
AIS Derive ROT
- Derive ROT from HDG: (Only SEAiq Pilot) When enabled, Rate-of-Turn (ROT) information from AIS for Own-Ship is replaced with values derived by SEAiq. See the dampening setting below. This can be helpful when AIS reports accurate heading but not Rate-of-Turn or if the Rate-of-Turn information has a problem. If AIS/NMEA reports accurate Rate-of-Turn information, you should not use this feature. This feature is only supported with live Own-Ship data from NMEA/AIS. It is not supported with Virtual Boarding, NMEA Playback, or simple (non-AIS) NMEA feeds.
- ROT Dampening: (Only SEAiq Pilot) This controls how much dampening to apply to Derive ROT from HDG feature above. Dampening is used to decrease the impact of occasionally spurious data, at the cost of somewhat less responsiveness. Normally, more dampening results in more accurate ROT but longer delay in detecting it. Conversely, less dampening results in less accurate ROT but faster responsiveness. Three levels can selected from. This setting has no effect unless Derive ROT from HDG is enabled.
Standard WiFi Devices
Extra Connection (Advanced)
- Load Device: Load NMEA WiFi and Bluetooth settings for a saved device. Pres EDIT to remove unneeded configurations.
- Save Device: Press this button to save your NMEA WiFi and Bluetooth settings.
- Configuration Name: This is the name of the current configuration.
- Advanced Settings: Advanced settings for NMEA and AIS.
NMEA Server (All but SEAiq Pilot)
SEAiq supports forwarding GPS information to other devices as a new NMEA feed. This is useful, for instance, if you have an iPhone with GPS and a WiFi-only iPad without GPS. You can install SEAiq on both devices, configure the iPhone as an NMEA server and the iPad as an NMEA client.
In the example above, you first need to make sure both devices are on the same WiFi network. Then get the IP address of the iPhone by going to Settings, WiFi, and selecting the name of the network being used. Then pick a port number to use. Here we use 10000.
- iPhone (NMEA Server Settings)
- Server Enable: ON
- Server Port: 10000
- iPad (NMEA settings)
- Enable: ON
- Use NMEA/AIS GPS: ON
- Use UDP: OFF
- Host: IP address of iPhone
- Port: 10000
The SEAiq NMEA server does not currently forward AIS data, only GPS-related data (location, course, speed, etc).