S.Seifullin Kazakh Agro-Technical University

Technical faculty

Department of Agricultural and post-harvesting Machines

LABORATORY WORK

) on subject) on subject on subject «Adjustment and linkage of Agricultural machines»

Theme: Precision Farming

Astana 2012

Considered and approved at the meeting of Methodological Council of S.Seifullin Kazakh Agro-Technical University Protocol №___ «___»_______________2012

«APPROVED» Chairman of Methodological Council of S.Seifullin Kazakh Agro-Technical University Protocol №___ _____________A.M.Abdyrov «___»_______________2012

Authors: Yeskhozhin К. – Candidat of Techical Sciense, Associate Professor of the Department of Agricultural and post-harvesting Machines.

Educational-methodical __________ is designed for training on discipline "Fundamentals of tractors" for students on specialty 5B080600 - "Agricultural techniques and technology"

Educational-methodical instructions are made according to the working curriculum of specialty.

Methodical instructions are intended for students of specialties 5В080600 – « Agricultural techniques and technology» and includes laboratory occupation tasks and independent work, educational literature lists and control questions for self-examination.

Reviewers: Doctor of Technical Science, Professor S.O. Nukeshev;

Reviewed and recommended at a meeting of the Department of Agricultural and post-harvesting Machines .

Protocol № ___, of "__" ___________ 2012.

Reviewed and recommended at a meeting of the methodical commission of Technical Faculty.

Protocol № ___, of "__" ___________ 2012.

1. To study the positioning in precision farming

3. Concepts of Precision Farming Systems and Required System Elements

4. Yield Mapping

5. Soil and Weed Mapping

6. Control of Field Operations

7. Information Management

1. Precision farming

Yield monitors are a recent development in agricultural ma­chinery that allow grain producers to assess the effects of weather, soil properties, and management on grain production. They are a logical first step for those who want to begin practicing site-specific crop management or “precision agriculture.” The accu­racy of these devices depends on appropriate installation, calibration, and operation. Therefore, it is essential that grain producers understand how the yield monitor works to improve their grain enterprise.

Figure 3.1. An integrated precision farming system.

Crops and soils are not uniform but vary according to spatial location. Large-scale nonuniformities have long been countered with different cropping practices in different regions. But precision farming responds to spatial variability within individual fields or orchards. This leads to a more cost-effective and environmentally friendly agricul­ture by

^• Increasing food production

^• Optimizing the use of restricted resources of water and land

^• Reducing environmental pollution

^• Engaging the efficiency capabilities of intelligent farm machinery

^• Improving the performance of farm management

Precision farming concepts include:

^• More accurate farm work by better adjustments of settings and by improved monitoring and control mechanisms

^• Localized fertilizing on demand in accordance with the variability of soils, nutrients, available water, and plant growth

^• Weed and pest control by localized crop production needs

^• Automated information acquisition and information management with well-structured databases, geographic information systems (GIS), highly sophisticated decision-support models, and expert-knowledge systems in integrated systems con­nected by standardized communication links (Fig. 3.1).

Precision farming is not a fixed system, but rather a set of general concepts that may have different physical realizations with

Different soil types under different climate conditions

Different farm management systems and production levels

Different mechanization solutions

Benefits of Using a Yield Monitor. The yield monitor is intended to give the user an accurate assessment of how yields vary within a field. Although a yield monitor can assist grain producers in many aspects of crop man­agement, the device was never intended to replace scales for marketing grain.

A yield monitor by itself can provide use­ful information and enhance on-farm re­search. Yield data can be accumulated for a specific load or field, thereby facilitating the comparison of hybrids, varieties, or treat­ments within test plots. For example, all yield monitors can measure grain mass and har­vested area on a load-by-load or field-by-field basis. This feature allows an operator to get instantaneous readout in the field of accumulated grain weight, harvested area, and average yield. With many yield moni­tors, these values can be exported to a per­sonal computer and stored in nonvolatile memory for further analysis or printing via specialized software packages or more standard word-processing and spreadsheet software. Season sum­maries of harvested areas might then be used to settle custom harvesting charges or to keep track of production from indi­vidual fields when it is impractical to scale grain trucks. With a yield monitor, a producer also can conduct on-farm variety tri­als or weed control evaluations without the need of a weigh wagon. Such on-farm comparisons help producers fine-tune crop production practices to their soils.

Geographic Information System (GIS) is mapping software that can link information about where things are with information about the location, e.g. soil type, vegetation, topography, roads, etc.  Combining GPS and GIS can direct tractors, four wheelers, aircraft, or persons on foot to desired field locations.  Additionally, these systems can be programmed to direct mechanical operations, e.g. variable-rate sprayers, fertilizers, or seeders, etc.  This technology is revolutionizing many agricultural operations.

Global Positioning System (GPS).

Global Positioning System (GPS) is a technology that can locate positions or navigate the user to a location. Most vehicle guidance systems in agriculture use GPS to determine the position, speed, and heading of the vehicle, and steer the vehicle in the proper direction. The GPS system uses signals emitted from a constellation of 24 satellites orbiting the Earth to determine the geographic position of the receiver on the earth’s surface. The satellites emit signals in two frequency bands, referred to as L1 and L2, to improve the accuracy of the position signals. The nominal accuracy of GPS systems is 10 to 20 meters with single-band receivers and 5 to 10 meters with dual-band receivers. The accuracy of the GPS signal is affected by atmospheric con­ditions, obstructions, reflections, and the visibility of satellites. When the receiver has a clear view of the horizon and can see many satellites, the quality of the position fix is good and the receiver can accurately determine its position. However, if the weather is bad, and there are obstructions that block the signal or cause reflections, such as trees and build­ings, the position signal becomes much less reliable. Similarly, if there are few satellites in view, or if they are low on the horizon, the position signal also becomes less reliable and has larger error.

GPS units consist of a receiver, antenna, display screen, and/or lightbar for tracking. These units can be handheld, carried as a backpack, mounted in mobile equipment, or an integral part of a desktop computer depending on desired application and accuracy. 

Differential GPS (DGPS) uses a base station or a special signal to supply a correction value to the receiver’s data.  This combination can provide accuracy from 30 feet to inches depending on type of equipment.  Base stations use post-processing of data.  Differential signals for real-time applications include Omnistar (worldwide L-band satellite signal), Landstar (L-band satellite signal), Coast Guard beacon (where available), WAAS (Wide Area Augmentation System), and RTK (Real-Time Kinematic). 

There are some techniques that can be used to minimize some of the errors in the positioning signal. Differential GPS (DGPS) receivers use an existing GPS receiver at a known static location on the ground, called a base station, to correct for errors in the position of the mobile receiver. The difference between the actual location of the static receiver and the measured location of the static receiver (the error) is calculated and broadcast on a radio to the mobile GPS receiver. The mobile receiver then subtracts the error from the measured location of the mobile receiver, correcting for errors caused by the visibility of the satellites and the atmospheric conditions. As the distance from the base station increases, the accuracy of the differential correction decreases, since the signals at the base station will be slightly different from the signals seen by the mobile GPS receiver.

Setting up a local base station for differential correction doubles the cost of the GPS system and poses additional hassle for the user. Several systems have been set up to provide differential correction signals without requiring a local base station. In North America, the most common forms of differential correction are the Coast Guard Beacon, fee-based satellite correction, and the Wide Area Augmentation System (WAAS). The Coast Guard Beacon was developed by the United States Coast Guard to improve the accu­racy of GPS receivers used to guide ships through navigable waterways. Although the Coast Guard Beacon signal is freely available, it is only available near navigable water­ways, and the accuracy of the signal degrades as distance from the waterway increases. Several subscription-based differential correction services are available from providers, including Omnistar. The subscription-based services are widely available and have good accuracy, but they do require an annual fee. Another system used for differential correc­tion in North America (WAAS) was developed by the Federal Aviation Administration to provide accurate and reliable differential correction to aircraft using GPS to aid in guiding the aircraft and landing. WAAS operates similarly to the fee-based satellite correction systems, but requires no subscription fees. Similar systems are being developed in other parts of the world, Euro Geostationary Navigation Overlay Service (EGNOS) in Europe and Multi-Functional Satellite Augmentation System (MSAS) in Asia. Typical accuracies for DGPS systems are less than one meter.

Other types of GPS systems used for highly accurate navigation are Real-Time Kine­matic (RTK) GPS systems. With RTK-GPS systems, a base station must be used with a radio to transmit the data to the GPS receiver. The RTK-GPS receivers monitor the carrier phase of the GPS signals to help improve the accuracy. The accuracy of RTK-GPS systems is typically within 1 cm, provided that the mobile receiver is within several miles of the base station. Unfortunately, RTK-GPS receivers do require a base station and they are expensive.

In addition to position, GPS receivers can also give accurate information on heading and speed. GPS receivers can output heading and velocity information that is much more accurate than what can be calculated based on the difference between the last two posi­tions. Most overlook the usefulness of the heading and speed information, but it is helpful in developing guidance systems for vehicles.

If multiple antennas are used on the vehicle, additional information can be determined with regard to the pitch, roll, and yaw angles of the vehicle. These systems, called vector GPS systems, are often used on aircraft. Stanford has also used a vector GPS system to guide a John Deere tractor. Since the vector systems provide pitch, roll, and yaw infor­mation, they can be used to compensate for the error in vehicle position due to the tilt of the vehicle. Although these systems give additional useful information, they are more expensive since they require additional antennas.

If only one antenna is used, inertial sensors or tilt sensors can be used to correct for the position of the antenna when the vehicle is operating through uneven terrain. Tilt sensors use accelerometers to measure the tilt angle of the vehicle by measuring the change in direction of the pull of gravity on the vehicle. Once the pitch and roll of the vehicle are know, the GPS location can be transformed into the vehicle coordinate system to deter­mine the exact location of the vehicle.

GPS systems vary in accuracy and cost when used with different guidance strategies, including operator assist guidance systems, such as light bars, to completely autonomous vehicle systems. GPS systems that use freely available differential correction signals are accurate enough to use with the operator-assisted guidance systems. The fee-based differential correction signals provide enough accuracy to guide semi-autonomous vehicles for planting and spraying applications. However, RTK-GPS systems are often required when centimeter-level accuracy is needed for such operations as cultivation.