GNSS (Global Navigation Satellite Systems) [Professional]

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Introduction

Global Navigation Satellite System (GNSS) is a satellite navigation system with global coverage that uses satellites to provide autonomous geo-spatial positioning.^[1] The satellites provide signals from space that transmit positioning and timing data to GNSS receivers. The receivers then use this data to determine location^[2] and also provide navigation or tracking the position of something fitted with a receiver.^[1]

In agriculture they are used to auto guide and track agricultural vehicles (the guidance of vehicles using satellite-based positioning equipment). This technique reduces skips and overlaps, lower’s operator fatigue and enhances the ability to work in poor visibility conditions. Another important use is on the management of crop health.^[3]

Remote sensing devices are devices that are able to collect data from distances. This is achieved by light reflectance collected by instruments in airplanes, orbiting satellites or hand-held devices. Remotely sensed data provide a valuable tool for evaluating crop health. One more useful use of the GNSS systems is fertilizer, soil and seed management. Specifically, on the go sensors mounted on tractors can take soil samples that will give information about the soil and plan for future fertiliser’s management. Also, by placing the plants on the appropriate distances (correct spacing), allow the plants to benefit at maximum from the sunlight and soil moisture. That can happen, by using a computerised soil map of a field on a computer fitted on the tractor along with a GNSS receiver. In this way, farmers will have information about they’re position in the field, allowing the adjustment of seeding according to suitable spacing.

In terms of agriculture Galileo is used in combination with EGNOS-The European Geostationary Navigation Overlay Service. EGNOS is Europe’s regional satellite-augmentation system (SBAS) that is used to improve the performance of global navigation satellite systems (GNSSs), such as GPS and Galileo. EGNOS uses GNSS measurements taken by accurately located reference stations deployed across Europe. It provides high accuracy and integrity.^[5]

Find out more about EGNOS:	Learn more about the Galileo system:

Uses of the GNSS systems

GNSS systems are used for:

• Precise spacing for planting vines and trees
• Creation of auto-steerable rows for ease of operations
• Reduction of labour costs and increased efficiency
• All the operational functions where the variable rate principle is involved are connected with in-field motion of machinery^[6]

Benefits from GNSS systems use

• Precision soil sampling, data collection, and data analysis, enable localized variation of chemical applications and planting density to suit specific areas of the field
• Accurate field navigation minimizes redundant applications and skipped areas, and enables maximum ground coverage in the shortest possible time
• Ability to work through low visibility field conditions such as rain, dust, fog and darkness increases productivity.
• Accurately monitored yield data enables future site-specific field preparation.
• Elimination of the need for human “flaggers” increases spray efficiency and minimizes over-spray.^[7]
• Reduction on fuel consumption.
• Reduction of waste and over-application of fertilizers and herbicides.
• Seeds consumption reduction.
• Extended equipment lifetime due to optimized usage.^[8]

The agricultural applications (yield monitoring, plant mapping, precise weed management etc.), require many sensors to acquire data from the field. Due to this, all this data can be linked together through a map by means of the location information provided by the GPS or any other GNSS receiver. With this type of precision agriculture data, prescription maps can be created for planning future farming tasks.^[10]

All the global systems operate in a very similar manner to the GPS system but each has its own unique qualities. Galileo (which is a European navigation System), uses more modern modules than GPS and it is operating in three bands: E1, E5 and E6 and offers an encrypted Public Regulated Service and enhanced Search and Rescue (SAR) service. Eighteen satellites are operational today.^[12] The GPS constellation consists of 24 satellites plus several spares flying in Mid-Earth Orbits (MEO, 20,000 km), orbiting the earth at a rate of approximately twice per day.

GNSS enables guidance technologies to accurately operate manned and/or unmanned vehicles with or without operator’s intervention.

References

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[1] en.wikipedia.org/wiki/Satellite_navigation

[2] gsa.europa.eu/european-gnss/what-gnss

[3] Ikokou B. G (2013), GNSS applications for agricultural practices, PositionIT, pages 59-65.

[4] earth2observe.eu/?p=5126#prettyPhoto

[5] gsa.europa.eu/egnos/what-egnos

[6] Bochtis D., (2013), Satellite based technologies as key enablers for sustainable ICT-Based agricultural production systems, 6th International Conference on Information and Communication Technologies in Agriculture, Food and Environment (HAICTA 2013), Procedia Technology pages 4-8

[7] gps.gov/applications/agriculture

[8] Giannopapa C., Oren G., (2011), Views on Public Perception and International Aspects of the European Space Flagship Programmes Galileo/EGNOS and GMES, European Space Policy Institute, ESPI, Report 33, pages 28

[9] Griepentrog, H. W., Jaeger, C. D., & Paraforos, D. S. (2013). Robots for field operations with comprehensive multilayer control. KI-Künstliche Intelligenz, 27(4), 325-333

[10] Pérez Ruiz, M., & Upadhyaya, S. (2012). GNSS in precision agricultural operations. Intech.

[11] ontariograinfarmer.ca/2015/12/01/understanding-precision-agriculture-9

[12] manuals.spectracom.com/TS/Content/TS/Topics/OthGNSSsystems.htm

Feature Image Source: therobotreport.com/top-10-technologies-in-precision-agriculture/