A single module to provide position and heading

[bazzaa]

My first post. Here goes.

I work in oceanography which involves working on a great variety of vessels big and small. Sometimes I need to place instrumentation on the seabed using a crane or some sort of lowering arrangement and sometimes just free falling stuff. On such occasions it is nice to have a chart plotter to show where the vessel is in relation to the place where I want to deploy the instruments. Sometimes there is one onboard but its seldom in a place where I can see it from my location on the deck.

What I want is a module that can provide position and heading data to my laptop which will be running Opencpn.

I have used a hand held GPS and a separate flux gate compass before but this uses 2 separate serial inputs which is sometimes inconvenient.

I was thinking along the lines of Arduino and cheap GPS and compass gadgets that could be put together to output the data that I need over a single serial output fairly rapidly, say 10 Hz.

Has anyone done this? Or perhaps it already exists, amongst drone enthusiasts maybe.

[CatNewBee]

It is called smartphone or tablet.
Just use the built in sensors and a app of your choice, opencpn or Navionics or Garmin or whatever there is available for Android or iOS.

[barnakiel]

Good smartphones and tablets have both sensors plus pressure etc.


barnakiel

[bazzaa]

ok - but I want to be able to see the display in sunlight out on the deck.

I have a high end laptop with a display that is readable in sunlight so I want to use it.
Also, my smart phone is not very smart. I don't think it has a compass and I am not sure about the update rate of the gps. (Samsung J6).

[smac999]

lowrance point 1. but it's nmea 2000. harder to get into PC

[GordMay]

Greetings and welcome aboard the CF, bazzaa.

[barnakiel]

Originally Posted by bazzaa

ok - but I want to be able to see the display in sunlight out on the deck.

I have a high end laptop with a display that is readable in sunlight so I want to use it.
Also, my smart phone is not very smart. I don't think it has a compass and I am not sure about the update rate of the gps. (Samsung J6).

Move your A and test that phone. I can't do it for you.


Download an app and go walking this allows you to see gps update times.


Some apps get course data if available on the chipset. Test one or two before giving up - sometimes the device has the sensor but the App is not capable of bringing it up.


Our Samsung Chat has the sensor. Likely J6 too then ?



Gps refresh is pretty irrelevant. I think they all update at least 1 per second, unless you tune down / filter their data.


b.

[barnakiel]

And what is your problem with forwarding your smartphone signal to your laptop?


Leave the smartphone inside, bridge over BT or wifi.


Use the laptop with smartphone data.


yes? no? maybe?


b.

[dennismenace111]

Use your laptop with a USB GPS!

[leighatsea]

I use GlobalSat 05-BU353-W10 GPS with OpenCPN on my laptop. Connects through UBS.

[CarinaPDX]

I will have to do a little research. GPS modules with magnetic compass and 3-axis accelerometers and gyros are readily available, and very cheap - they are used by the drone community. IIRC uBlox sells modules that have them internally, but I don't remember seeing them retail. They are intended for dead-reckoning car navigation systems, through tunnels and canyons (urban or otherwise). The problem is that they typically use I2C or SPI interfaces, not RS-232 (which is often not really RS-232 either - that was my Saturday trying to determine what my new GNSS receiver was actually putting out). There is probably a USB adapter that could work - I'll take a look tonight.

Greg

[CarinaPDX]

The cheap drone modules have the gyro/accel/heading/baro sensors onboard, but they use separate interfaces so will not solve the single-interface problem (http://reyax.com/wp-content/uploads/2017/09/RY835AI.pdf). Also the non-GPS sensors would require I2C to USB adapters, and might not be formatted usefully.

The uBlox module I mentioned is for dead-reckoning and uses gyro+accel internally, and does put it out in NMEA format over USB. See this for specs: https://www.u-blox.com/sites/default...-15015679).pdf If you want to try it out you can buy an EVAL board, plus cable and USB interface (at bottom) from https://www.csgshop.com/product.php?id_product=235 . You might need to use the Windows uCenter app to set it up, or ubxtools in GPSd on Linux. Whether it is worth the $100+, the time to learn and set it up, and the risk of not having what you want, is for you to consider.

Individual GPS and gyro modules can easily be interfaced with an Arduino, which in turn could be connected with your computer. I don't know of any "shield" that contains both. The Pi does have "hats" that have everything you need and then some, such as https://copperhilltech.com/pican-wit...-raspberry-pi/ and https://shop.sailoog.com/openplotter...ssier-hat.html . Or individual GPS and orientation hats could be combined. This approach definitely is going to require effort and some software skills to accomplish. Of course it would be possible to build a freestanding Pi computer with small color display and sensors for your purposes, which would eliminate the need for the laptop; you would probably use Android with OCPN.

Frankly I like the earlier recommendation to buy a decent tablet with sensors (not all of them have the orientation sensors). Costco has them, by Samsung. Install OCPN on the tablet and be done with it.

Greg

[barnakiel]

All true and you may ask OpenCPN developers if their App collects the heading data from such a sensor. Because the phone may have the sensor but it does not mean OpenCPN van read the sensor data.


Unfortunately, the phone we have does not run OpenCPN (too small memory, old phone) so I cannot test this for you. Maybe someone with a newer Samsung could,


Cheers,
b.

[fdr14127]

I would explore the gpsd driver utility which downloads with some utilities that might answer your needs. If you post on their blog they might have some good advice as there are a ton of people using their code to solve all kinda these requirements. We use our Raspberry Pi to put this kinda data out on the vessel web for all to see.

[bazzaa]

What with covid and all that, I have not done much on this project for a while. Bit lately I have experimented with several devices that should be able to provide heading data but I have been disappointed by all of them for tricky calibration routines or poor tilt compensation.

Just recently I got a CMPS14 module. This module comes ready calibrated and it seems to be very good on tilt compensation. Mind you I have not tried it on an actual boat yet.

I have made a prototype that uses GPS data from a ublox unit. An Arduino Nano takes in the GPS string using SoftwareSerial then spits it out over USB. Next the heading value is read from the CMPS14 via I2C and dressed up to resemble an NMEA heading string and spat out over the USB right after the GPS string.. At the moment both strings go out at 1 Hz and look like this:-

$GPGGA,132732.00,5148.47862,N,00225.61164,W,1,07,1 .59,61.9,M,48.6,M,,*77

$HCHDM,240.4,M
$GPGGA,132733.00,5148.47905,N,00225.61167,W,1,07,1 .59,62.5,M,48.6,M,,*7A

$HCHDM,240.3,M
$GPGGA,132734.00,5148.47912,N,00225.61172,W,1,07,1 .59,62.6,M,48.6,M,,*7C

$HCHDM,240.6,M
$GPGGA,132735.00,5148.47926,N,00225.61178,W,1,07,1 .59,63.0,M,48.6,M,,*77


The problem is that Opencpn does not recognise the heading data. Now I know that it does not have the checksum at the moment but I have unticked the the box on Opencpn that decides whether its needed or not so I was hoping that this is not the problem. I have even tried sending totally fake data that does have the checksum and it still doesn't like it.

Interestingly, the extra line feed is not evident when looking at the same data on the Arduino serial monitor. I wonder if this is a clue that any of you may recognise.

Next I am going to try to add the proper checksum but its trickier that I thought due to the format that the heading data comes in. I would include my code but I am not sure how to just now.

If anyone can shed some light on this problem I would be very grateful to hear it