Slide background

SEANEXX - USB AIS Receiver

Abstract

The SEANEXX is used to receive AIS messages and to output them on a virtual COM port. With a corresponding PC software (e.g. HTerm, OpenCPN), the received data is displayed as text or graphically. The SEANEXX and the associated configuration tool operate under the standard Microsoft Windows, Linux and Mac OS X operating systems.

The SEANEXX is supported by the Raspberry Pi. The AIS data can be transmitted via WiFi to a tablet or smartphone. For visualization several apps are available, u.a. SailTracker, AISView, BoatBeacon, NV Charts, iSailor or iNavX. The Raspberry Pi supports UDP and TCP protocol and can be configured via a web interface.

The SEANEXX is available in four models:

  • RX100: AIS receiver only
  • RX110: AIS receiver with integrated GNSS
  • RX200: Dedicated two-channel receiver for simultaneous reception of both AIS channels (AIS1 and AIS2)
  • RX210: Two channel receiver with integrated GNSS

 

Customer: FT-TEC Electronics GmbH

What is AIS?

AIS stands for Automatic Identification System and is a communication system that operates over registered channels within the maritime mobile VHF band as a self-organizing time slot method (161.975 MHz and 162.025 MHz). It is based upon an open, unencrypted protocol with which information is transmitted and received autonomously with no interaction from ship or operating personnel. In addition to this autonomous mode, capabilities are also provided for the transmission of short, safety-related messages when there is human interaction.

The information generated autonomously and transmitted to other ships or to shore via a broadcast is dynamic information such as position, speed and course, but also static and cruise-related information such as draft and ship type. Transmission is at regular intervals, whereby the interval depends on the speed and any course changes of the particular ship. This information is processed by the receiver and can be visualized on a display, generally an Electronic Chart Display and Information System (ECDIS). Current position information is referenced geographically with the respective ship identification of the AIS stations received and displayed on a digital map.

For further information see www.allaboutais.com.

See also OpenSeaNav, AIS-SART, Wi-Fi AIS receiver/multiplexer.

Activities/Services

  • design, schematic and layout of the assembly
  • firmware implementation
  • EMC testing
  • implementation of an USB bootloader
  • implementation of the application and web interface on the Raspberry Pi
  • 3D rendering for the user manual and various advertising material

Picture Gallery

Field Test

Location

  • Italy, Venice, Lungomare Dante Alighieri
  • GPS coordiantes: 45°25'40.40"N / 12°25'45.44"E
  • Date: 2015-08-30
-

Equipment used

  • Notebook ASUS F551C
  • OpenCPN 3.2.0
  • SEANEXX RX210 (5400020A02)
  • Clip antenna CDV-H6A-5SP

Procedure and Results

The clip antenna was mounted on a 2.5m round wooden stick. Thus, the antenna base was about 4m above sea level. The SEANEXX receiver was connected via USB hub to the notebook and the data was visualized in OpenCPN with CM93 maps. The results are shown in the screenshots below. The level of map detail has been reduced to highlight the relevant information of the range test.

The web page www.marinetraffic.com displays live AIS data. The screenshot below compares the received data of the RX210 with the data at Marine Traffic. The red circles in this case correspond to a radius of 5NM. The receipt rate up to 20NM is very high. At longer ranges, some AIS targets are no longer received, but this is generally observed for all wireless connections, since radio signals are superimposed by noise sources such as cellphone towers or radio station and not arrive correctly at the receiver. In this case, the smaller the input power at the receiver (i.e. the greater the distance of the AIS transmitter), the greater is the impact of the interference source on the wanted signal.

AIS sends messages repeatedly and in very short intervals, thus occasionally lost data is not problematic.

As the results show below, distances up to 490 NM (AtoN), 215 NM (Class A) and 98 NM (Class B) are possible. However, it is noted, that in particular AtoNs, base stations and Class A transponders use high transmission power (> 12.5W), hence the achievable range is much higher as compared to Class B transponders (2W). Mostly the antennas of AIS stations are mounted 20m or more above sea level, which significantly affects the possible distances. Ranges of 490NM are not typical, especially since AIS radio works on line-of-sight. Such ranges may occur due to atmospheric reflections. AIS is used primarily for collision avoidance, where the real benefit is limited to 5 to 10NM. The test shows however, that the world's smallest dual-channel AIS receiver delivers remarkable reception quality.

Video Recording