Farmer develops tractor control

Creator of Ag Open GPS, Brian Tischler, sits in the electronics lab he built in his basement. He uses the lab to develop projects or fix farm electronics. | Robin Booker photo

An Alberta farmer has developed open source software capable of driving tractors autonomously with the use of their existing GPS.

AgOpenGPS is a free program farmers can download onto a tablet, which users then plug into a port located on the back of most GPS systems.

The tablet also needs to connect to an arduino, which is a small, open-source computer hardware item, or mini controller, that turns things on and off based on simple programming and costs about $5.

“The USB from the computer (or tablet) sends information to the arduino. The arduino listens, and as soon as AgOpenGPS says turn a relay on, the arduino will activate the command,” said Brian Tischler, designer of AgOpenGPS.

The relays the arduino trigger can activate most tractor functions, including auto steering, as well as implement up and down controls.

Related story: Arduino leaps from school to farm

During Tischler’s presentation at Farm Tech held Jan. 30-Feb. 1 in Edmonton, he had a tablet running the AgOpenGPS autonomous field work simulation, and the tractor proceeded through the simulated field with no operator intervention.

The program is capable of doing the same thing on a real field, it just needs to be connected to an arduino that can control tractor functions.

This board allowed Tischler to eliminate the tractor environment with inputs, including a steering motor that provides feedback for the program. | Robin Booker photo

Last year, Tischler updated his program and the arduino-controlled functions on his seeder to provide autonomous seeder off and on, as well as section control during planting.

This spring, he plans to attempt to completely automate seeding at his Mannville, Alta., farm, including headland turns, with AgOpenGPS.

“It will autonomously seed the whole field. It will lift it up at the ends, it will turn on and off the sections based on the headland, and it will finish off the whole field without touching a single button. That is all running on a single tablet,” Tischler said.

A limiting factor with the system is how the relays controlled by the arduinos are integrated into the tractor’s controls.

“It’s going to take some work to getting it working on my tractor because the tractor I want to do it on doesn’t have a lot of the CAN bus (Controller Area Network), and some of the more convenience things.”

nect to any Can bus-equipped equipment. It allows operators to read and control things such as steering and hydraulics and monitor engine temperature, R.P.M. and oil pressure, etc. | Robin Booker photo

“It’s more mechanical in terms of linear actuators to control speed and that sort of thing,” Tischler said.

To enable AgOpenGPS to auto steer his tractor, Tischler temporarily mounted in his cab a battery-operated drill motor with a small rubber wheel that contacts the tractor’s steering wheel.

“If you need to go left a little bit, the motor will correct the steering wheel a little to the left, and right and that sort of thing. Again, I just used a little arduino, whose purpose is to tell the motor which way to go, and how fast to get there,” Tischler said.

Growers can connect AgOpenGPS to tractors with CAN bus technology with a CAN bus readier, which is an interface board that connects directly to any CAN bus equipped piece of equipment and allows users to control things like steering and hydraulics, as well as monitor things like engine temperature, RPM, and oil pressure.

Part of the autonomous function of AgOpenGPS is a program called AgraBot, a platform for autonomous grain carts and field work such as harrowing and rolling.

This is a bluetooth relay board and is used to control objects with a smartphone. It has four relays on it to control tailgates and turn on/off sprayer booms, augers and hydraulics. | Brian Tischler photo

“It (the program) just follows a predefined path, and stays within a geo-fence, basically a mapped fence around the field. If it goes outside that, it just shuts down. It just goes and does its thing because things like rolling, harrowing are the epitome of brainless,” Tischler said.

Combine operators will make a line in AgOpenGPS program, call the cart over with their tablet or phone, and the grain cart will follow the line at the same speed.

Tischler recently bought a LIDAR (light detection and ranging) remote sensing system for $120. He plans to mount it on the front of his tractor and include its data into Ag Open GPS’s autonomous function for better obstacle avoidance.

Tischler said he designed AgOpenGPS because he needed it for his farm. His tractor is equipped with an RTK autosteer unit but it lacks a display, and because he seeds with a disc drill, it can be difficult to see where to set in after a headland turn.

Tischler didn’t want to pay $15,000 to $20,000 for a new RTK GPS with a display, so he looked at the information coming out of the back of the GPS, hoping to attempt his own mapping.

He became frustrated when trying to understand how agricultural GPS systems work because little information is available.

“Nobody has released anything. You can read the patents and you can kind of get an idea of how they generally work. We use GPS in tractors and we know how they work, but we don’t know how they work in the background.”

In some tractor GPS systems, a blue or green line indicates where to travel, which Tischler said is basically a collection of graphical triangles.

Once the simulated triangles within the GPS program are driven over by the implement, the tractor is pulling, a path within the program is created, which the subsequent field pass will follow.

“How I think a lot of these systems work is they determine the position of the tool, then mathematically determine if they’re inside one of those triangles. If they are inside one of those triangles, then you know that you’re driving over where you’ve driven before,” Tischler said.

His approach, which is graphical instead of mathematical, drew upon his background in game programming and experience with an open graphic language program called OpenGl.

“It was kind of funny. In Combine Forum, I asked a question; ‘does anyone know how section control works?’ A guy just jokingly said, ‘it’s really easy, you can seed where it’s green.’ I thought that wasn’t helpful.

“Then about a day later I thought, he’s right. OpenGL, since it’s displaying, why don’t I just read what’s in the display buffer, and if it’s green, it’s applied, if it’s not green, it’s not applied,” Tischler said.

By taking the localized area of where he is with the RTK GPS information feed into his tablet, as well as the graphical information of what has been covered, he was able to write a program that graphically displays on his tablet his progress on the field down to two to four inches of accuracy.

“I just use the GPS information coming out of the back of the receiver. It just constantly, five or 10 times a second, tells you where you are, latitude and longitude, how fast you’re going, and your heading. There is other information also, but that is the gist of it,” Tischler said.

With an accurate log mapped out on AgOpenGPS of where he’s already seeded, he was able to enhance the program last year with section control, as well as to turn his seeder on and off at headland turns.

“Every GPS, at least in the tractors, have a RS232 port on the back, and it spits out this MNEA sentence. That sentence is your latitude and longitude, your heading, your speed, that sort of thing,” said Tischler.

He said the drone industry has pushed down the cost of GPS technology because many more products are on the market.

For instance, he said Emlid and Swift Navigation offer full RTK navigation for about $2,000.

These products can be combined with AgOpenGPS mapping software and an arduino for a cheap system capable of automated section control, seeder on and off, and soon, a system capable of taking total control during seeding.

Tischler licensed AgOpenGPS code as open source because he wanted to help grow a community.

“The biggest reasons that I brought this out as open source is so a community of us farmers could learn and understand better how some of this stuff works. And we can share ideas and we can build things better than under the restrictions of a company.”

He said he’s translated AgOpenGPs into seven languages due to requests and it seems to be well used in Russia. However, there is no way for him to tell how many people use it.

A cat skinner from Indiana asked Tischler to improve the resolution of the altitude in the program so it could be used to install drainage pipe. So, based on the AgOpenGPS framework, Tischler developed Open Grade.

“What it does is it gives a cross profile. You map out your trench, and it shows you a vertical map, and you can create a cutline. It shows you where the original dirt is and how much dirt you have to remove and that sort of thing,” Tischler said.

Ditching programs cost thousands of dollars, but it took Tischler only three days to convert AgOpenGPS into Open Grade, which can be used for ditching.

AgOpenGPS has also been modified for use in orchards, and work is being done so that it can integrate OpenCV (Open Source Computer Vision Library) to measure leaf density and control automated application rates based on these measurements.

Tischler said if growers are interested in trying AgOpenGPS they can downloaded it for free from GitHub at

For video tutorials on the program, Tischler’s YouTube channel is FarmerBrianTe, found at

For a discussion of the technology on The Combine Forum, visit

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