perjantai 9. elokuuta 2013

The starting point

The starting point is our 35ft sailing vessel with basic navigation instrumentation including a chart plotter, echosounder, mechanical log and wind instrument.

The target is to have all current & other nice to have boat data available on wifi as data for other applications such as iNavX and a simple (sic) platform to create whatever navigation displays I can think of displayed on browsers connected to the boat's wifi.

Current inventory:
My first experiment was to get AIS targets to display in the navigation apps on the iPad. Once I got the cable connected with correct polarity I was able to stream the AIS data as UDP packets on the local wifi and have it show up in iNavX on iPad.

AIS targets from VHF in iNavX on iPad

For lack of time I decided to postpone Raspberry installation for this season and instead hooked the VHF up with the plotter to get usable AIS display no matter the state of my Raspberry setup.

As to the goal that I'm after: the built in layouts on my i70 are somewhat lacking. You can configure different layouts for a bunch of numbers on a display that is really readable, but the visualizations are pretty lame. Or what do you think of the graphical temperature "gauge" in the picture below? Another good example is history graphs that have no indication of the range of the values.
Dumb sea water gauge
Since it appears that the manufacturer is not about to give us incrementally better firmware build your own is starting to sound like a viable option.

And btw I have currently no way to upgrade the firmware on my i70 with my minimal N2K setup...

So what I'm after is an easy way to develop new gauges and displays. One example would be a multi-gauge in the likeness of B & G Sailsteer: one gauge to visualize multiple data points in an easy to grasp way. As a starting point I wrote some Javascript based on Steelseries gauges to mimic Sailsteer.
Sailsteer-like gauge drawn with custom JS.
Freeboard is a real life project with somewhat similar goals, but I would rather skip the Arduino and have just the Raspberry directly off the N2K bus with PICAN and Canboat.

2 kommenttia:

  1. Hello,
    Thanks a lot for your very interesting bolg.
    I just bought an old sailing boat equipped with 2 analog sensors ( deep, temperature & speed). I had a quick look on Raymarine solution, and ITC-5 + I70 is fine but expensive, and after reading your post, I would say that I70 is a bit to much expensive . I wonder if we can get rid off the I70, and control the sensors with the Raspberry only. I read that I70 is mandatory to control and calibrate devices, but after all everything is per formed through NMEA2000 messages. Do you think it is doable ?
    Thanks a lot

  2. My guess is that calibration with ITC-5 + i70 combination actually changes parameters in ITC-5, which affects the output of ITC-5 and all instruments in the network get the calibrated data. Doing this from a Raspberry Pi via NGT-1 is possible in theory, but it would require reverse engineering the N2K messages from the i70.

    But if you are going to use the data only via Raspberry Pi there is nothing stopping you from creating your own calibration algorithm and applying that to the data once you have it.

    This blog is pretty old, I've since moved on to Signal K activities. I urge you to take a look at and Signal K servers. The place for this kind of logic would be Signal K server, where calibration and enhancement of incoming data stream should take place.

    Please join the discussion at!forum/signalk