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Basic GPS guidance systems

GPS (Global Positioning System) and other GNSS (Global Navigation Satellite systems) have been available since the 1990s. These systems consist of an array of satellites which transmit very accurate time signals. GPS receivers can detect these time signals from multiple satellites and use the information to provide the user with location and position information. GPS receivers are commonly used in road vehicles, smartphones and smart watches to enable users to navigate, track activities and even receive local weather information. 

The use of GPS equipment in agriculture is not new, but the development of the technology and falling costs of technology has resulted in new equipment which can aid many farming applications.  

Agricultural GPS systems come in may shapes and sizes offering a wide array of features to help guide the operator and equipment during field work. The entry point for most is a manual guidance system. 

A manual guidance system, unlike the more expensive auto-steer systems, has the job to help the operator follow a programmed path. This is normally by means of a lightbar positioned on the front of the tractor. The lightbar will indicate if the vehicle is “on route” or has deviated to the left or right. The operator has the job to steer the vehicle to ensure the target light remains in the middle of the light bar. 

Entry level guidance systems often consist of a single battery power unit which can be placed at the end of the tractor bonnet. The unit can connect to a mobile device using Bluetooth and is managed with a mobile app.  

The tractor operator will manage the tractor speed and direction, aiming to ensure a precise application rate and avoiding waste by reducing overlapping and gapping.  

Typically, the user will set the desired bout width in the app, to avoid overlap or gapping when applying fertiliser of sprays. Once in the field for the first time, the operator will record their A-B line by driving a straight line, normally, along the longest field boundary. The lightbar will assist the operator to ensure they are driving parallel to their A-B line at the desired bout width. 

As well as being guided by the lightbar, the mobile app can display information about the speed, distance and area covered. 

Advantages – Cost effective and accurate application 

Entry level guidance systems benefit by having a simple, quick setup enabling the operator to start field work without delay. Such systems can be moved from tractor to tractor with little or no installation or programming required. There are no tractor requirements, such as auto steer compatibility or ISO bus functionality, making this type of equipment suitable for tractors of all ages. 

Accurate application rates of product will reduce waste and cost. Field operations are much easier for the driver, especially when trying to drive wide bouts in fields which have low grass cover, which make it difficult to see tyre tracks. 

These systems typically cost less than £1000, making them a viable option for many farm businesses. 

Disadvantages – limited features and manual steering 

Entry level systems will not have the precise position information available to more expensive GPS solutions. Basic GPS systems typically offer accuracy of <30cm, which should be sufficient for fertiliser and spraying applications on grassland. More precise GPS systems are available, but at a greater cost. 

Entry level guidance systems may not offer features such as headland turn management, curved A-B lines or facilitate complex field shapes. More advanced GPS systems will offer more features, but at both a higher cost and increased complexity. 

These entry level guidance systems offer no auto-steer functionality, so the driver has the job of manually steering the tractor. 


For many farmers who have not used any GPS based guidance system, entry level GPS systems is a great way to take advantage of many benefits field guidance system can offer, but without the high cost and complex operation of more feature rich systems. Lowering costs, avoid waste and reducing environmental impact, by ensuring that application of product is accurately delivered in the field should be the primary reason why any grassland farmer would consider using GPS guidance. 

For more information, search online for Agricultural GPS system, to find suppliers of GPS systems.