Thursday 13 December 2018

Navigation Instrument WiFi connectivity on a Cruisers budget

Setting up WiFi connectivity on a Cruisers budget

Scouting made easier using a mobile WiFi unit to send depth and positioning data to a tablet to make/update navigation charts. I put together a portable WiFi enabled GPS/Sonar to transfer depth and position data to make a sonar chart on the fly. Personal HD depth contour charts develop in real time as your boat (or tender) moves through the water. 

On board I also connect a WiFi unit with built in multiplexer to send the AIS and Instruments data to  our navigation laptop running OpenCPN.

Scouting made easier.

Scouting new anchorages has always been a bit of a hit and miss affair. Turning up at a remote part of the planet and wanting 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. These anchorages off the beaten track often lack detail on the charts we have.  Exploring new areas late in the afternoon made us uncomfortable due to the angle of sun not allowing us to see into the water easily. Getting our keel caught up with a falling tide has the potential to be disastrous.

Opppps caught on a receding tide, deep water was just to port

Potential anchorage but the chart is lacking detail

A Google Earth chart overlay can help show some detail but lacks depth information

We have tried several different methods to help quickly scout out areas we were interested in moving through. 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 manoeuvring in tight quarters, we couldn’t easily keep up with the setting changes to keep the obstacles on the display. Then as we were coming to grips with the operation and a couple of niggling problems, the company was sold and the new owners 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.
Rather large forward facing sonar transducer ready to go

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 a bommie or sharp pinnacle. We were searching for a reliable alternative and being full time cruisers a cheap solution would be nice.

A viable alternative was to install an active depth transducer in the tender. I thought 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 later follow the track made while we were in the tender 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 transducers we could find were just 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 having a pre summer sale 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. At the time the price was better than an active depth transducer and we have a GPS and sonar display screen in to the deal. One of the items that attracted us to this unit 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 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, but I guess it worked for the week-end fishermen who could afford to 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 Android tablet that we have an active subscription to Navionics on.  This simple video on YouTube from Navionics gives an over view of the Live Chart concept

On the tablet is the same bay as previous, but now has depth information after a couple of passes in the tender

A close up of the depth information detail
Our 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 on our laptop 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 transmit AIS information from the on-board AIS 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. However you will have to ensure the program (app) will recognise and display AIS data.
NMEA0183 to WiFi bridge 

As a side note; these units are great for those of us who went out and brought iPads/Android tablets then found the units do not have a built in satellite GPS receiver. In our case we didn’t realize we didn’t have a satellite GPS receiver in one of our tablets until we fired up the navigation programs away from the dock and found they couldn’t position us. Now you can run the navigation programs on the iPad/Android tablet that doesn’t have a satellite GPS, you can send in the positioning data on the Wi-Fi connection. You don’t even need an expensive GPS, a feed off your on board GPS or a hand held with an NMEA0183 output will work a treat.  

Short video of AIS on an iPad using the YAKKER

Our Hook Up

The Wi-Fi network NMEA Bridge is tiny and doesn’t consume very much power. After some quick experimenting we found the NMEA output of our small Lowrance chartplotter could easily be connected to the Wi-Fi Bridge and the depth and positioning data could be sent to the Samsung tablet. The actual wiring was simple, two power wires and a single data wire connected to the Wi-Fi unit. The output of the small Lowrance Chart plotter/GPS is NMEA0183 (RS422) with 2 wires A (+) and B (-), so I simply connected A (yellow TX A) to the RX connection on the YAKKER, NMEA to Wi-Fi Bridge.

Our chart plotter uses the NMEA0183 RS-442,  both styles RS422 & RS232 of data transfer types are shown
Our hook up RS422 depicted in the previous drawing by the TX_A and TX_B

This type of connection is fairly common, most Garmin handheld would use this connection 

If I was using a battery (standalone) powered GPS (like a Garmin 72,72H or 73 hand helds) that was not powered from the same source as the Wi-Fi Bridge I would also connect the grounds together. It is best to power both units from the same source, whether it is an external standalone battery or the vessels battery bank.
If using a self powered unit I would connect the grounds together as shown here with a common ground

So back to scouting in the tender, 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 and had it connected to the YAKKER Wi-Fi Bridge.
Battery and YAKKER unit fitted into a water resistant box
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. The reason I send the GPS info to the tablet is to reduce the power consumption of the tablet. I turned the tablet GPS off to conserve power and get better endurance from the battery.

Box sealed up and ready to go

NMEA0183 configuration screen showing sentences to be transfered

Sample of configuration screen
Setting up the Wi-Fi Bridge unit was simple. If you’re not tech savvy don’t let the jargon scare you away. The unit will boot up into access point mode, you will see it on your phone or laptop just like you see the free Wi-Fi connection at your local cafĂ©. Just follow the instructions in the PDF file that is sent to you when you purchase the unit. Log on to the device named Yakker with the password 12345678. Once I was logged on, I opened a browser window and using the address and go, I was then connected to the Wi-Fi Bridge. What I did change was the SSID (username) and password. Once you change these and hit the submit button you will have to close off your connections and reconnect with the new identity.

Other than changing the SSID and Password I found the default settings did work straight out of the box when we first got going. After a couple of test runs I found that what I believe are due to limitations of the tablet I needed to increase the baud rate of both the WiFi data and the chartplotter. The reason for the change was because the read out and boat movement on the tablet was a jumpy on the tablet screen. Once I changed the Baud rate and reduced the amount of data sent from the chartplotter the update was a lot more fluid. Keep in mind I had to change the Baud rate on both the Chartplotter and the Wi-Fi Bridge so they were matched.

If you’re interested in an Australian made product or products that won’t break the bank here is the web site:

If you use EBay the units can be purchased from the online EBay shop. If you are an Ebay member you can get better deal, look here first due to the better price, the units are made by a small company in Morayfield (just north of Brisbane) and posted from Australia.
We are using this 2 port unit to send AIS and GPS data to the laptop running OpenCPN

We have since purchased a 2 Port, Wi-Fi Bridge YAKKER, we can feed the on board GPS and AIS into the unit and use the GPS positioning and AIS data for OpenCPN we run on the laptop. The 2 Port YAKKER does away with the need for a separate multiplexer to combine the two data streams. Best of all the cost for this set up was a fraction of the cost of imported unit/units.
Some other units from the range available

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