OpenPlotter (Ref.1) is a Linux based Operating System that runs on the Raspberry Pi computer. The Raspberry Pi is extremely popular in the education field. It is well documented, compact and requires very little power. This makes it ideal to form the basis of an electronics navigation system for a small craft. In the previous two posts we looked at how to install OpenPlotter on the RPi, how to remote it from your laptop and then how to connect and view GPS on OpenCPN. In this post we will look at how to add AIS reception using the RTL-SDR to the OpenCPN display.
AIS Installation & Connection
Connect the RTL-SDR to the RaspberryPi using an extension USB cable or directly to the USB port. I prefer to use an extension cable so as not to exert leverage on the port when the antenna is connected. Add an appropriate vertical antenna. Now under the Raspberry/OpenPlotter/Settings locate the SDR VHF app (Fig.1). Highlight the app, and install using the icon in the top right hand corner. This will install all the software required for the RTL-SDR. This may take a few minutes. When this is finished, under Raspberry/OpenPlotter locate and select the SDRVHF item. You should now see that AIS is installed (Fig.2). If you haven’t already calibrated your RTL-SDR, then you can calibrate it now. Open the calibrate window. In Toronto, there is a lot of GSM850 activity, so that is what I used to calibrate. Highlight the detected device, select GSM850, enter a gain of 30 and then hit “Get Channel” (Fig.3). This will detect the strongest channels, and takes several minutes. Once this is complete, enter the channel number and hit “Get PPM”. This will give you the PPM error which you enter for the selected device. Once this is completed, open the Processes tab. Check the AIS box and start the process. This will add the AIS to the ServerK. Now open ServerK to check that you are receiving GPS & AIS traffic. Fig.4 shows both the GPS location and AIS traffic. Fig.5 YouTube Video shows the complete process.
AIS & GPS Reception Toronto Harbour
Please send your comments, questions and suggestions to:
#2. – “OpenPlotter – Navigation System on RPi”
#3. – “OpenPlotter – GPS Connection”
#4. – “RTL-SDR for AIS”
#5. – “AIS GMSK Modulator – Scicos Simulation”