Turn your PC into a map plotter, absolutely free? It can be done by downloading OpenCPN, an open source program developed by a group of enterprising sailors with a knack for programming, thanks to which you can plan your routes before departure. But that’s not all: you can interface your laptop on which OpenCPN is installed (via NMEA 0183 protocol) with the on-board instruments to display data on the screen: not only position, then, but also information about speed, AIS, Radar and whatnot.
WHAT MAPS DOES IT READ?
The program can read maps in Bitmap format, also called “raster” maps: the accepted format is BSBV3. Files in this format usually have the extension .CAP or .KAP. Some tools can be found on the web to convert raster maps to this format; with some plug-ins, you can also make maps in BSB4 and nv-chart formats readable. Vector maps are also accepted, in S-57 ENC format.
THE OPERATION FOR “BEGINNERS”…
Although some people on the web say that while OpenCPN is a stable product, it lacks some functionality, it is still a free product worth testing and can become a very useful navigation aid. Interfacing with the on-board electronics is done by connecting the NMEA bus to the PC’s serial port (you can use a Serial-USB conversion cable if your computer does not have one). Simpler still is to connect a handheld GPS directly to the serial port (by setting the port number and bit rate in bits per second in the OpenCPN configuration: however, the program will only display the boat’s position on the map and the data transmitted by the GPS).
…AND FOR PROS.
For those who want to get serious about connecting all the instruments to the serial port (you can even control the autopilot!), there will be the problem of the communication protocol: for example, Raymarine uses the private SeaTalk protocol, so you will be forced to equip yourself with a little box that can convert SeaTalk data to NMEA. Since this is an Open Source program, it is open to modification by third parties, so there are numerous plug-ins available, such as one that allows you to view Google Earth, World Magnetic Variation, Voyage Data Recorder, AIS -radar, SAR, and even a LogBook.