GPS: the applications and availability are expanding. Uses on the farm:
- Map the Harvest (utilizing GPS and yield monitor technology)
- Plant Using Variable Rates (utilizing GPS and variable rate technology)
- Map farm land for insurance and data purposes (utilizing GPS and mapping software)
- Make parallel swaths (utilizing GPS and navigational equipment)
The tutorial on GPS from Trimble Navigation Limited gives rules of thumb for GPS pinpointing. Navigational systems like GPS are utilized for a variety of farming applications. This kind of technology is especially handy when adding fertilizer, lim, or a pesticide, or when keeping tabs on large grain harvesting, drills or planters.
Navigation by GPS has the ability to supplant sprayer foam and markers for planters or drill-disks since GPS is capable of driving in accurate rows up and down a field without as much overlap or skipping of field area. This way, farmers won’t overdo it when applying chemicals, which will in turn protect the environment’s water. GPS also allows a farmer to repeat the way his tractors go annually so there aren’t as many negative side effects to farm equipment traffic.
Using a GPS-outfitted ground vehicle to apply farming chemicals has quickly become quite popular, so more an more manufacturers are adding such equipment to their machines. Whipker and Akridge did a study in ’07 showed that showed more than 80% of the ones who did custom application used GPS with a manual light bar guidance mechanism to add farming chemicals. Around 30% stated that their farm made use of GPS auto-steering for one or more of their applicators.
Why GPS and field work should go hand in hand.
Farmers desire their vehicles to be self-run for a lot of reasons. The biggest reason is so that they are freed from constantly operating and adjusting the drive in addition to constantly maintaining their equipment and ensuring high-quality farm management. This is understandable since a driver must do many things while controlling the vehicle.
Since farming vehicles have become bigger, more powerful, multi-functioning and faster, there is a lot for an operator to handle. It’s easy to make expensive mistakes that can hurt the environment, the vehicle, finances, or the farmer himself.
The Common Foam Marker
Foam is currently the most popular way to prevent overlapping or missing areas on a field when fertilizing or spraying pesticides. Foam drops to indicate the width of a pass, so the vehicle can line up along the foam on the return pass. This is done by an air-pressurized tank of foaming liquid. The pressure causes an overflow into an adjacent container that then overflows onto the field in little blobs.
Usually these foaming machines are attached on one side of whatever applicator is being used. Sometimes, when there is no boom, the foaming machine is attached in the middle. Vehicle drivers can see where the equipment has gone on the field by looking at the foam trail.
Navigational Equipment Like GPS
There are somewhat cheap pieces of navigational equipment that can visually show the driver where the vehicle is compared to where it has driven already. It alerts the driver to what steering changes need to be made. These are called parallel-tracking devices. A farmer can buy one of several kinds of parallel-tracking devices. The light bar system has a line of LEDs in a twelve to eighteen-inch plastic tube which is connected to a GPS receiver. This bar is mounted, inside or outside, in front of the operator. The lights indicate if the vehicles is going the right way, or if it’s drifting to the left or right of the desired path.
The farmer can program the system to be more sensitive or allow more distance between passes. Aerial appliers have been using GPS navigation systems since the ’90s. The GPS software can record where an implement is and can tell a driver exactly where it should go based on where it’s already been. Even if the driver needs to stop working mid-field for a re-fill or to get out of bad weather, a GPS navigation system can always pick up where it left off without fear of overlapping and over-spraying. Higher technology even shows the paths the vehicle has gone, and where it currently is, on a screen. Previously, it was only possible to use GPS navigation for straight drives, but now there are systems that can handle any desired path. This kind of GPS navigation paired with a variable-rate applicator has the ability to show exactly what has been applied, where. This is great data for the farmer to see the timing and placement of all applications. For example, if an area in the field is to wet to work on, the computer will record exactly where the area is so the farmer can go back and treat the area when it is drier. No flag markers necessary.
Even more advanced GPS technology, like auto-steering, can not only guide the driver and map the land, but steer the machines on their own. This can happen by attaching a piece of hardware to the steering column or the electro-hydraulic steering. How accurate this technology is is dependent upon how good the data processor is and how well it corrects itself. Improvements in accuracy will probably lead to a higher price tag. There are three levels of these navigational systems:
- Under a Meter: These systems might make error a couple of feet apart one year to the next, but usually the error is within a foot from one pass to the next. They utilize Wide Area Augmentation System (WAAS) such as Coast Guard beacons or satellites. The cost ranges from 6 to 15 thousand. They are good for tilling, some fertilizing and applying some chemicals, harvesting, and seeding. Such hardware can be moved from one machine to the next easily, so one auto-steering system can control any and all of the farming equipment in turn. Agriculture that necessitate extreme accuracy need a system that has better accuracy.
- Under 10 Centimeters: With this set of devices, a farmer will come withing 4-8 in. of where the system said he was the previous year, and within 5 in. between passes on a field. This is possible by use of two receivers or utilizing a base station along with a subscription for private satellite differentials. This higher accuracy allows growers to utilize auto-steering for most farm activities. These systems can be anywhere from $15 – 25 thousand in addition to paying for the subscription which can be $1,500 every year.
- Centimeter Accuracy: These systems are made possible by utilizing local bases and RTK, or real-time kinematic devices. Whether a farmer goes over the same path within 10 minutes, or after several years, the error is purportedly around 1 in. Such high accuracy is great for placing drip-tape, leveling, strip tilling and anything else that might call for high precision, in addition to all other tasks, as well. Not only can these systems find a vehicle geographically, they can also sense and correct unruly handling in its pitch, roll or yaw. A system like this would cost $40-50 thousand (no fees necessary).
Foam v. GPS
Some pros that GPS has over foam are:
- Accuracy: Foam-markers might have a farmer skipping or overlapping around 10% of the land. Cut that percentage in half with GPS navigation. An experienced operator can even drop that percentage down to 1.5.
- Speed: It remains accurate even when a vehicle goes faster. A vehicle navigated by GPS can go between 13% and 20% faster than one with a foam marker, according to Buick an White’s study in ’99. Understandably, this depends on the field’s conditions. When a field prevents high speeds, this advantage is nonexistent.
- Spinner Spreaders: GPS navigation can be used with them, while foam markers aren’t, since the spreader has no boom to hold a foam marker. Attaching a foam marker to the center would be tricky because of its width, still requiring the driver to make a huge judgement on where to drive for the next path.
- Ease: Anyone can learn how to operate a GPS navigation system, even if they aren’t savvy with computers. A farmer can get used to a system with 30 minutes of practice.
- Growing Crops: Foam falls through and isn’t really visible, making it easy to skip or overlap on a field, while GPS works just fine with growing or tall crops.
- Poor Visibility: Since GPS navigation doesn’t rely on optics, it can run in fog, at night, or through thick dust. When there is a lot to be done (think: planting and spraying season) the work can be done regardless of light or conditions. In some places, night spraying would be better since the wind dies down and can also protect bee colonies living nearby. Be sure to check with the Extension specialists to see if spraying at night could be good for your farm’s needs (remembering that a plant’s leaves change at night).
- Weather: Foam markers don’t do so well in hot, dry conditions, or in big fields. Foam dries up before the driver turns the vehicle around. Yet GPS isn’t affected by temperature, even the cold (when a foaming agent might freeze).
- Cost: GPS systems don’t require so many on-going purchases. They don’t have parts that might clog, or parts that move and wear out. Often, systems updates are free to the customer, while farmers using foam markers have to constantly buy dye, foam and tank cleaner.
The big repeating budget item for GPS systems is the subscription for satellite differential correction which can by between $600 and $1,500 a year. Some farmers already subscribe for the sake of monitoring their fields. In Virginia, most farmers can utilize the Coast Guard beacon or WAAS, which are free and work fine for jobs like spinner spreaders and dry fertilization.
Spraying accuracy needs to be under 10 cm, and the GPS unit seller will be able to inform the customer of what differential correction needs there are in his area. More information is available in Precision Farming Tools: Global Positioning System (GPS) by the Virginia Cooperative Extension.
- Driver Fatigue: GPS navigation of any kind will ease the stresses on the driver. Even using the light bar systems, the driver is relieved of the need to look to the side or to the back. They look forward, confident that they are driving straight-lines with minimal overlap.
- Setup Time: While foam marker tanks requiring filling, dyeing and cleaning, GPS systems just work in less than a minute after ignition.
- Wind and Bounce: Wind can blow your foam and a rough patch of dirt can bounce your boom making the foam mark inaccurate. These things don’t affect a GPS system.
- Reduce Pesticides: Fewer overlaps mean less pesticide. Take the statistic from earlier: if overlap is cut from 10% to 5%, then that’s also 5% less pesticide being sprayed. That also goes for seed and fertilizer, so the GPS system can help the environment and the farmer’s profits.
- No Entering Sprayed Areas: A driver can map sprayed places with a GPS map without getting down and dirty amongst the sprayed crop.
When thinking about adding a GPS system to a farm’s management system, the purchase should be motivated by a specific farm need, thoughts of how it will fit into the farm’s operations and comprehension of accuracy and errors. Terrain, tracking implements and a certain vehicle’s dynamics should also play into the decision. The customer should make sure to properly install and align the system. The GPS will not work as well if the steering system is low quality, the land is sloped, or the implements are not aligned. One important ability of a GPS system is following patterns of vehicular movement and giving feeding to the auto-steering system so it can correct if necessary. Almost all GPS system can guide a vehicle in straight lines, and some can do more advanced configurations.
Though GPS is usually intended for steering, some systems intake data and make maps of applications and yield. They may even have the ability to control variable-rate dispensers. These extras make it so that more than one task on the farm is aided, increasing efficiency in several farming activities. That spreads the cost of the equipment across several activities. A GPS data map can show what was applied and when on any given point on the field. GPS systems can even adhere to “no-apply zones” that may be dictated by regulations for the sake of gardens, residences, schools, nurseries or ornamental crops. This documentation that is able to record when, where, and how much of an agent was applied, may come in handy for a farmer’s records of chemical and machine use. In extreme cases, these maps could be used as a legal defense to show that a farmer followed regulations.
Products for GPS navigation differ in size and user-friendliness. Some are easy to set up within an hour, while others are more challenging. Some have touch-screens with colorful displays that are easy to intuit, while others have minimal graphics and have a steeper learning curve.
The reason a field should be flat for GPS navigation to work well is that the slope changes how a vehicle moves. Any movement, roll, pitch or yaw (sideways, forward and backward, or around the vertical axis) change the where the GPS antennae is in relation to the supposed center of the vehicle. This will cause errors. To make up for this, some units also have a gyroscope, accelerometer or other meters to measure where the vehicle is. More basic incinerations can only compensate for roll and pitch. More advanced units measure dynamics in six degrees, allowing the system to work well on all kinds of terrain.
Some sellers also sell extra systems for implement tracking. These systems compensate for the mathematical geometry that the implements track and can change depending on the direction of the vehicle so that the implements stay lined up. Other tracking systems based on optics or crops help position the implements according to the rows that are already there.
Counting the Cost
There are many pros to using GPS navigation instead of other markers like foam, especially when a driver’s estimation is required visually (as is the case with spinner spreaders). If a farmer is already using a GPS system for monitoring or mapping fields, or for sampling the soil, an added navigation system will likely increase the farm’s efficiency and lower negative environmental impact that come with over-spraying. The navigation system also relieves the driver of the tiring job of handling a vehicle or stressing over exactly where to spray or fertilize. Also, this technology will show non-farmers that high technology is helping growers farm better and safer.
Maps of where applications occurred aid farmers in proving that they are using spraying according to regulations.