Professional Grade Centimeter Accuracy GPS 'on the cheap"

Discussion in 'Boat Modification Journal' started by Longjohn119, Apr 10, 2017.

  1. Longjohn119

    Longjohn119 Well-Known Member

    As anyone who has checked out my blog knows I made and use an external GPS on my Lowrance Elite 7 Ti with an active (amplified) patch antenna that sits right over the transducer to minimize the error. Other wise you'll have an error that is approximately the distance between the transducer and the finder times 2. (I've explained this on my blog also) I recently upgraded my GPS package with a new uBlox NEO-M8N GPS module that not only picks up the US GPS system but also the Russian GLONASS system ..... More 'birds' means better accuracy and even with the antenna sitting on the sill of my west basement wall with 2 big trees out front I average 8 US birds and 3 Russian birds in less than ideal conditions. Already I'm seeing a big improvement but still not centimeter accuracy. (But better than the standard 1-2 meter accuracy of standard GPS units in finders)

    However the NEO-M8N module can also accept correction data from a RTK (Real Time Kinematic) NTRIP (Network Transport of RTCM via Internet Protocol) network. Living in a heavy agricultural state (Likely the most productive agricultural land in the world) Iowa with a heavy emphasis on 'Precision Farming' the state runs a free publicly accessible NTRIP network across the state. So basically what I'm doing is using an old smart phone to access the network and then will use the phone's Bluetooth to transfer the correction information to my GPS unit which also has Bluetooth capability (I knew I stuck that Bluetooth module in there for a reason last year) and my NEO-M8N module will use that correction data to give accuracy down to a few centimeters. This is essentially an IoT (Internet of Things) application and AT&T Wireless is offering a 2G network SIM card for IoT applications for 10 bucks which lasts 6 months or 500 Mb of data which if my estimates are correct will give me over 200 hours of operation. A farmer from Cedar Rapids who has become an area expert also is offering a free Android App to help you access the IaNTRIP network (Or any other NTRIP network) as well as help set up your Bluetooth connection to the GPS module

    So basically my costs are about $25 for the Arduino controller and 'prototype 'shield, $7 for the Bluetooth module $30 for the NEO-M8N GPS module and $10 for the AT&T SIM. Plus the old Chinese smartphone that I paid $70 for 4 years ago. Actually there is no reason you couldn't use your main smartphone and data account other than your phone is going to be tied up and anyone that has had a smartphone for more than a couple of years probably has an old one sitting around after an upgrade. Since it is slow speed data the smartphone doesn't even need to have 3G or 4G, just the old standard GSM 2G (AKA Edge) data capability.

    So for under $100 (Not counting the smartphone) I'll have a centimeter accuracy GPS feeding my Elite 7 Ti chartplotter/finder for precision mapping ..... More details to come as I further develop the system after I read a couple hundred pages of tech literature for the uBlox module and the Iowa NTRIP network which is a Leica GeoSystems 'Spiderweb' network which is both highly rated and well documented. I don't expect much for problems though since Leica uses uBlox GPS and Bluetooth modules (Class 1 100 meter range) in their line of ruggedized tablets and and handheld GIS data collectors and both being Swiss companies you know the systems are made to work with each other.

    This technology is advancing rapidly thanks to all the guys experimenting with drones and buying these modules by the millions which has made the technology dirt cheap and accessible. The NEO-M8N units with a built-in patch antenna, case and mount (and a magnetic compass chip) are selling on eBay, Amazon and Chinese surplus venders (BangGood, Fasttech, etc.) for as low as $20. The drone guys are also the ones that made autopilot technology like used in the Motorguide Pinpoint GPS and Minn Kota iPilot systems possible at an affordable price point ..... So don't cuss those drone guys, we should all be thanking them for advancing the State of the Art and lowering the cost of precision GPS and autopilot systems from several thousand down to a couple of hundred in just a few years.

    I don't care what anyone says, I love the 21st Century ......
  2. Pipe Rat

    Pipe Rat Well-Known Member

    What did he just say? LOL Go for it John

  3. Catpaw

    Catpaw Well-Known Member

    I was so confused after reading that I had to lay down and go to sleep... Anyway thanks for a informative post John.
  4. metalman

    metalman Well-Known Member


  5. Longjohn119

    Longjohn119 Well-Known Member

    Well to simplify I'm creating a device known professionally as an RTK Rover (Google it and check out the costs) that normally sells for several thousand dollars for around 100 bucks that can be added to any chartplotter or other device that has a NMEA-0183 input using mostly Open Source technology and hardware and that will increase the accuracy of your GPS position from 1-2 meters down to as low as a couple of centimeters ..... or up to a 100 times increase in accuracy.

    Why? Well because I can, because I want one for myself but also I want to push manufacturers into producing these devices for the fishing and boating communities at an affordable price ..... Over half the states already have free publicly accessible RTK networks running either Leica or Trimble based networks that use the Open RTCM3 protocol so your only other costs besides the Rover is some cellular data charges which are pretty cheap since it's slow speed data, the packet size is 299 bytes and the Iowa system (And likely most others) sends 2 packets per second which comes to a tad over 2.2 MB an hour meaning a 500 MB data SIM would get you about 220 hours of operation for a cost as low as $10 ..... Or free if you already have a smartphone with an unlimited data account.

    Actually if the manufacturers ever got their act together there is no reason I couldn't make this device work with any system with Bluetooth such as the Elite Ti, HDS Gen3, and the new Minn Kota iPilot system ..... Adding this to the Bluetooth enabled iPilots would give it positional and anchoring accuracy at least 10 time better than it has now and would blow the competition away ..... All they would have to to is reflash the firmware (normal upgrade process for the customer) so the Bluetooth will pair with it .... All you would have to do is provide the device with power and pair it like you do any other Bluetooth device such as Minn Kota's Bluetooth Heading Sensor.

    When it comes to Digital Signal Processing of sonar transducers these guys are geniuses and I tip my hat to them but when it comes to modern technologies like WiFi, GPS and Bluetooth they are all 10 years behind the curve ..... Why in the heck am I hooking up NMEA 0183 and NMEA 2000 cables to a device that has both WiFi and Bluetooth networking built in? Why am I hooking up expensive NMEA 2000 cables to a Point 1 GPS Heading sensor when they could ditch the NMEA2000 conversion hardware and put in WiFi or Bluetooth for the same price and likely less? Then all I'd have to do is provide power and push a button to pair it up or enter an IP address in the Finder/Plotter if it is WiFi

    And the most important question of all ..... Why can I use an Android Tablet to see and control the screen of my Elite 7 Ti but I can't get my Windows Tablets to do the same when hardware and operating system is more than adequate? I know this because I bought a dual boot Android/Windows 10 tablet 3 months ago but I have to boot into Android to use it with the finder ..... BTW it looks awesome on the 10.1" 1920x1200 display even with Lowrance's poorly laid out app that eats up screen space (Are your programmers really too stupid to make autohide tabs and menus?) ...... however my mapping/surveying software all works in Windows and that takes precedent ...
  6. Catpaw

    Catpaw Well-Known Member

    John, Thanks for the explanation.
  7. I didn't think that civilian gps could be that accurate no matter what because of restrictions on the satellites. In other words even though your technology might be able to handle down to the inch the signal sent from the satellite was only good to within several feet, and that at certain times(like right after 9/11) that the accuracy was limited to 10s of feet.??
  8. Great info John!! Think n in Johns garage AKA the skunk works he is really building the new B-21 Raider and only works on boats as a cover up:sneaky::laugh:,,, Always good tech info from John ,,, tell ya one thing the cost of gps stuff sure has become more affordable,,,, bought a gps drone for $135 month ago dang thing can fly a half mile away hit a button and come back and land within a foot of where it took of from

    Attached Files:

  9. Catpaw

    Catpaw Well-Known Member

    That's cool Dale.
  10. Longjohn119

    Longjohn119 Well-Known Member

    President Clinton had those restrictions known as "Selective Availability" removed way back in the late 90's which is what threw open the door for an entire market sector. It was one of the most significant things Clinton ever did and the Economic Boost that came from it was vast and immeasurable since it is what made smart phones, drones, commercial navigation, etc. such a success and multi-billion dollar industries and created thousands of jobs. The only thing more significant that Clinton did was open up the Internet to the General Public by removing the restrictions on the phone companies and allowed them to become ISPs and offer Internet Access to the Public

    These two things led to some of the most significant advances in Human History ......

    Farmers here in Iowa have been using RTK centimeter accuracy GPS for farming since before the Iowa RTK network came online in 2008 ..... My Sister and Brother-in-Law both work in the IT department for John Deere and you should see the tech they are making for tractors and combines as well as their Big Data technologies ..... It's amazing but until the farmers start making money again so they can afford to upgrade it's gone so stagnant that thousands of Deere Manufacturing workers are laid off, some for almost 2 years now. The TPP did offer some hope of opening up new markets and raising the price of farm commodities but now that is long gone and farm commodity prices will remain stagnant for at least another year as they operate at near break even prices .... Having the most productive and efficient farming in the World does little good if there is no one to sell the record crops to ..... My fear is most of these highly skilled workers will end up going elsewhere and when the industry gets back on track Deere will have a severe shortage of properly skilled manufacturing workers like in the 1990's or even worse ..... Deere has had a problem finding educated workers for 25 years because making a modern computer controlled tractor or combine takes a lot more skill than making throwaway consumer devices like iPads and LCD TV's which are done mostly by robotics and CNC technology...... We are less than a decade away from autonomous tractors and combines and several farmers here have already made their own autonomous tractors using things like tablets and Google Glass. One guy I talked to a couple of weeks ago spent $8000 for a system 3 years ago so he could have a tractor pulling a wagon automatically drive over to his combine so he could unload it ..... The year before it cost him over $8,000 to hire someone to drive that same tractor and then sit around an wait an hour for the next load to be ready .... Last year he made an extra $8,000 in profit by not having to pay someone to sit around waiting most of the time while he drove the combine and picked corn.
  11. Longjohn119

    Longjohn119 Well-Known Member

    Well some bad news .... This module only does RTCM 2.3 (DGPS) which is pretty much worthless in North America because of the US WAAS system which does essentially the same thing, increase accuracy from 2.5 meter CEP to 1 meter or slightly below. The uBlox module that does the superior RTCM 3.1 true RTK and gives you the centimeter accuracy costs around 200 bucks. However I did find an outfit out of Taiwan that sells one for $50 plus shipping ($10-20) but it is GPS only and only a 1 Hz update. To go to 5 hz updates brings the cost to $75 plus shipping but to get the system I want which will use the Russian GLONASS system and the EU Galileo system that just came online in late December AND has 5 Hz updates costs around $125 plus shipping. I could make the Neo-M8N work for centimeter accuracy but that means getting another module and building my own 'base station' here at home and 'phone in' to that but I'd also need to have Windows computers running each GPS and processing raw UBX data and translating that to NMEA 0183 and I'd be limited to a 10 mile range with accuracy falling off the further you get from base and the Lost Grove Lake I'm mapping will be right on the fringe of the 10 mile range meaning accuracy out there would be 10's of centimeters. That's just too much hassle and I likely won't get much better than the 50 centimeter (0.5 meter) accuracy I expect from the new module because it uses the GPS GLONASS and Galileo systems at the same time. More locked satellites = better accuracy

    However the NEO-M8N is still a great upgrade for $20-30 and since it uses the Russian and EU systems as well as the American GPS system I'm getting HDOPs as low as .6 meters in my "Adverse Conditions" test setup (Patch antenna sitting on the sill of my basement wall with two large trees out front) and expect to do even better out in the open and will get even better yet over the next couple of years when the EU gets all their Galileo satellites into orbit, they only have about half in place so sometimes I can lock 4 and sometimes there aren't even any available. The other night I had locked 10 US birds, 2 WAAS birds for corrections as well as tracking, 4 Russian and 4 EU birds ..... That's 20 satellites plus WAAS corrections which isn't even possible using the US GPS system alone with just 24 active birds spread across the globe. Basically for $30 bucks I'm doubling my accuracy which is pretty cost efficient by any standard so I'm happy with that

    I was hoping that Minn Kota had also upgraded their GPS module in the new iPilots along with the Bluetooth and heading sensor upgrade but I cracked mine open and it still uses the uBlox NEO-6M which is the exact same module I'm replacing and used the last two seasons. It's still a good module but it can only use GPS or GLONASS but not both at the same time so the new NEO-M8N blows it away. However it is a pin for pin direct replacement so all Minn Kota has to do is slap in the new module and add a couple of tweaks to the firmware so I wouldn't be surprised to see them upgrade to it in the next year or two. Besides the NEO-6M just went out of production so when the existing stock is sold then that's it and Minn Kota will have to upgrade but like I said it's just a matter of slapping the new module on the existing PCBs and a firmware tweak.

    Maybe one of you Humminbird users knows for sure but I assume that they are also using the uBlox modules in the Humminbird finder/plotters since both companies are owned by Johnson Outdoors. That's a good choice IMO and uBlox has a good reputation in the high performance DIY drone community which is worldwide and maybe even larger than the marine/fishing market. The differences between the drone autopilots and the Minn Kota system are minor with the drones being slightly superior because they need altitude and and pitch control and boat autopilots don't. Both are mostly using the exact same STM32xx ARM-M microcontrollers, GPS and accelerometer/gyro/heading sensors and I bet Minn Kota is using the same Open Source code for the basic control and throwing their own code in for the user interface and memory functions just like all the finder/plotters run on top of Open Source Embedded Linux with a custom user interface and sonar processing code.

    That's why I say don't cuss those drones because without them driving the state of the art in autonomous control and positioning we wouldn't have affordable autopilot systems on consumer grade marine gear. They are also driving RTK/GNSS technology and I expect centimeter accuracy will be common on smartphones, tablets and their derivatives like consumer marine gear within 5 years or less. Currently the consumer cost of adding autopilot to trolling motors is about 400 bucks and I expect that will drop to 200 or maybe even 100 bucks in the next few years and not only that they too will all be centimeter accurate
  12. Longjohn119

    Longjohn119 Well-Known Member

    About 4-5 years ago I noticed one of my neighbors named his WiFi router "FBI Surveillance Van", obviously a prank so I named mine "The Pirate's Den" since my nickname has been Longjohn since the 80's .... Anyone scanning wifi on their smartphone while driving by or visiting a friend in the neighborhood is probably going "WHAT THE ___?"
  13. thats funny named mine DEA x-ray,,, kinda funny sure seams the one neighbor has less visitors then it use to
  14. Lol mines "DEA remote #359". I live in the sticks though o only friends and family see it. My mom still won't connect to it. Lol