Monday, 3 December 2018

Navigation system WiFi connectivity on a Cruisers budget

Navigation system WiFi connectivity on a Cruisers budget

 Scouting made easier using WiFi .

Scouting new anchorages was always a bit of a hit and miss affair. Turning up at a remote part of the planet and needing to stop for the night would often find us anchoring in places that sometimes didn’t offer the protection we could have had if we were able to move closer to shore.  Exploring new areas also made us uncomfortable, getting our keel caught up with a falling tide has the potential to be disastrous.
Electronic chart not showing any real detail
A google earth overlay helps fill in the blank detail but not the depths

We have tried several different methods to help safely scout out areas we were interested in. The first was a forward facing sonar, while the idea was good it turned out to be an expensive exercise. The draw back was the unit was very hands on and when we wanted the unit to be working at its best while maneuvering in tight quarters, we couldn’t keep up with the settings changes. Then as we were coming to grips with the operation and a couple of niggling problems, the company was sold and the new operators didn’t want to offer much support for the model we had.  So we shelved the forward facing sonar and at the next haul out we removed the transducer and unit.

Talking with others the overall consensus was to get out in the tender and have a look around. Scouting in the tender did have advantages but doing the sounding with a lead line was very time consuming and had the potential to miss that sharp pinnacle. We were searching for a reliable alternative and a cheap solution would be nice.

A viable alternative was to install an active depth transducer in the tender. The active transducers were a good idea, apply power and they would output a NMEA0183 depth string. We already had a Garmin GPS 72H.  This unit will take a NMEA0183 input and the depth could be displayed on the screen. We could follow the track made to bring Matilda in to the anchorage. The only minor drawback to this plan was if we were scouting in the shallower places we would need to make a good run in the deep passage to make a usable track. As it turned out the active depth transducer was way too expensive. So we looked at simple hand held depth reading units but they were lacking any real positioning, so there was room for error if we didn’t get it right when back on board Matilda.

We had all but shelved our plan when our local chandler was clearing out the stock of small chart plotter/fish finders. We got a Lowrance Elite 4 Chirp. The unit has a built in GPS and CHIRP transducer and due to its size it has low power draw. The price was better than an active depth transducer and we have a GPS and display screen in to the deal. One of the draw card items at the time was that we could up load (on the internet) our sonar tracks and get a chart for the area we had scouted. This sounded good but this required an internet connection to upload the data and then we had to wait for the finished product. This turned out to be a frustrating exercise, worked for the week-end fisher men who could wait for the next weekend.

We could copy our sonar logs off the unit, this was in Lowrance sonar file format .SL2. Unfortunately there isn’t much you can do with a .SL2 file, the program that was previously available would no longer work with newer computers. Then we found a program that would read the .SL2 files While this was a step in the right direction it wasn’t exactly what we had in mind. It would however be great for fishing and looking at what had gone under the boat during a trip, however it didn’t give us the chart to navigate on.

While we were searching for the program to read the .SL2 files we saw that Navionics could make a sonar chart live. What a great tool, we could have a depth chart done on the fly in the field so to speak, no waiting no delay and no internet needed.  The only drawback was we needed to be able to get the depth data into our Samsung tablet that we have an active subscription to Navionics.  This simple video from Navionics gives and over view of the Live Chart concept

The Samsung tablet has a built in GPS so positioning data isn’t a problem, however there isn’t a serial connection to input the NMEA0183 depth data. As luck would have it during our last trip back to Australia we had purchased a small Wi-Fi network NMEA bridge (YAKKER). The original plan was to connect it to Matilda’s GPS output so we could run OpenCPN wirelessly. This unit will allow applications to directly access NMEA0183 data over TCP/UDP connections. Now we can view vessel information from virtually anywhere on the vessel. The units will also support AIS information via the on-board receiver. So if your tablet has a built in GPS and you would like to add AIS data then this may be an easy way to do it. You will have to ensure the program (app) will recognize and display AIS data though.
YAKKER WiFi Bridge for $49 free shipping world wide

 Short video of AIS on an iPad using the YAKKER

Our Hook Up
This Wi-Fi network NMEA Bridge is very tiny and doesn’t consume very much power. After some quick experimenting we found the NMEA output of the Lowrance chartplotter could easily be connected to the Wi-Fi Bridge and the depth and positioning data could be sent to the Samsung tablet.
As a side note this is great for those people who went out and brought iPad's to run navigation programs on. Then later on found the units do not have a built in satellite GPS receiver. Now you can run the navigation programs on the iPad that doesn’t have a satellite GPS for a reasonable out lay, you can send in the positioning data on the Wi-Fi connection. You don’t even need an expensive GPS, a feed off your existing on board GPS or a hand held with an NMEA0183 output will work a treat. We have also found some AIS units out put GPS position data along with the data for the surrounding targets. So you may only need one connection for AIS and GPS data sent to your tablet/phone (smart device).
Simple one wire hook up, the requirement is that the YAKKER requires the same power source as the GPS/ChartPlotter

So back to our scouting unit, I set about working out how we could set this all up in the tender so we could scout areas of interest. I had a water proof box and a motor cycle battery we had purchased for a running light on the tender at night. It didn’t take long before I had the battery in the box, and had wired in the chart plotter connected to the YAKKER Wi-Fi Bridge.

The finished unit ready to go
To keep things simple I have a switch on the outside to turn off power to the YAKKER and the chartplotter. The only change I made to the operation of the chartplotter was in the NMEA0183 setting tab was to increase the output baud rate from 4800 to 38400. I then also set the transmitted NMEA sentences to only include GLL GGA RMC RMB and for depth information DPT and DBT. I found the shorter string of data was all we needed for the tablet. I am guessing the tablet wasn't  processing the data fast enough and this was causing display problems.  The reason I send the GPS info to the tablet was to reduce the power consumption of the tablet. I could leave the tablet GPS off to conserve power and get better endurance from the battery. Your tablet may not need a reduction of data over the WiFi you may need to experiment to check this out for your self. Don't forget you will need to set up your tablet/program to use the data. For some it will be simple others may require reading the manual, or a google search for others who have done it previously.

Config screen of our GPS unit, showing baud rate and transmitted data.

Inside the box showing battery fuse and YAKKER mounted on the LH side
RS422 is normally identified by the A+ and B- in the hook up drawings
I would use this RS232 hook up for things like a Garmin handheld. The ground wire shares battery ground.
I would use RS232 hook up for this Garmin handheld the battery ground is data ground

As a note if the unit has seperate battery (battery powered) I would connect the grounds together. In the above drawing I would put a connection from battery - (ground) and connect it to the - (ground) of the YAKKER.
Here is the web site,

If you use EBay the units can also be purchased from the online EBay shop.

Since making the mobile unit we have purchased a YAKKER 2 Port NMEA to WiFI bridge so we can feed the on board GPS and AIS into the unit and use the data for OpenCPN run on the laptop. The 2 Port YAKKER does away with the need for a separate multiplexer to combine the two data streams. 
2 Port NMEA to WiFi unit we are using to sent GPS and AIS data to our lap top running OpenCPN.

Some of the different units we have or are using