Poor Man’s Chart Plotter

Want a Chart Plotter powered with GPS, Inertial Measurement Unit (IMU), an AIS receiver, and free chart updates both raster and electronic? Want the flexibility to use your laptop, phone, or tablet to navigate by over WiFi without any expensive boxes?

With a little know how and some shopping on Amazon you can do all this for a fraction of the price of a new chart plotter and associated accessories.

  1. Raspberry Pi 3 ($35)
  2. Raspberry Pi 3 GPIO Connector ($20)
  3. 16GB MicroSD Card and Adapter ($8)
  4. HiLego Inertial Measurement Unit ($9)
  5. 12V USB Adapter ($10)
  6. Box for IMU ($10)
  7. Standoff Kit ($8)
  8. Ribbon Cables ($7)
  9. Barometer, Temperature, and Humidity Sensor ($9)
  10. NMEA0183 to USB Adapter ($20)
  11. GPS Receiver ($14)
  12. RTL-SDR for AIS
  13. Antenna for AIS Receiver ($22)
  14. MCX to PL-259 Adapter ($6)
  15. OpenPlotter Software (Free)
  16. Chart Plotter Software
    1. iNavx – Robust iPhone/iPad Application
    2. OpenCPN – Free Software for Mac, Linux, Windows, Raspberry Pi, Android
    3. GPSNavX – Excellent Navigation Software for the Mac

Simple Install

All of the parts above are not required to get started. At a minimum you’ll want to purchase the RaspberryPi (1), GPS Receiver (11), and MicroSD Card (3). This enables you to download the OpenPlotter software. The OpenPlotter documentation is very good and easy to follow. In short, you download an image file for the RaspberryPi and image it to the MicroSD cart. This takes care of the operating system and software installation. The OpenPlotter software creates a WiFi Hotspot for you. One important tip is to make sure you can plug the RaspberryPi into an Ethernet port on your home network. This allows you to update the software with one click. Once you are finished you’ll have a fully functional plotter with a dedicated GPS. You need to download a VNC Server client to connect to the OpenPlotter to configure the software. An alternative is to connect a keyboard, mouse, and screen. After you get things setup download one of the applications listed below, connect to the OpenPlotter AP, and add a new network connection for within the plotter software. This essentially gives you a NMEA0183 over IP connection and streams GPS sentences to you.

Intermediate Install

The next step to make your plotter even better is to purchase a Software Defined Radio (12). You’ll also want to buy an external antenna for the receiver. I use a stern mounted antenna for mine (13). The RTL-SDR has a MCX connector, so you need to buy an adapter to convert it to a PL-259 (14). Adding the SDR enables you to receive AIS signals and display them within your Plotter software. Follow the directions on the OpenPlotter website. This is a plug and plug installation.

Advanced Install

For an advanced solution you need to purchase items 2-9 on the above list. This provides you a IMU aka Heading Sensor, Temp/Barometer/Humidity Sensor, and interface to your NMEA 0183 devices. If you have an existing external GPS receiver you can connect it to your RaspberryPi instead of purchasing the USB GPS receiver. If you have a NMEA2000 network on your boat, there is a USB adapter made by Activsense that enables you to interface your RaspberryPi.

Here are some pictures of my setup:

RasperryPi onboard my Compac 23 Halfmoon.
RTL-SDR that enables the reception of AIS data.
Garmin GPSmap76 provides GPS to my OpenPlotter.
iNavX running on my iPhone connected to the OpenPlotter software.
OpenCPN running on a Amazon Fire tablet connected to OpenPlotter.

Building your own OpenPlotter is a fun and rewarding task. Even if you already have a plotter, this setup can provide you a fully functional alternative if needed. All it takes is a little bit of time, patience, and willingness to learn.

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