Global positioning system (GPS), components and its functions.pdf
0 likes1,951 views
The document provides an overview of the Global Positioning System (GPS), highlighting its components, functions, and significant role in precision farming. It details the space, control, and user segments of GPS, explaining how it facilitates accurate navigation, field mapping, and efficient agricultural resource management. Furthermore, it discusses errors that can affect GPS accuracy and explains enhancements like Differential GPS (DGPS) that improve positioning accuracy in farming applications.
Global positioning system (GPS), components and its functions.pdf
- 1. Global positioning system (GPS), components and its functions Geoinformatics and Nanotechnology and Precision Farming 2(1+1) Course Teachers Dr. M. KUMARESAN, Ph.D. (Hort.) School of Agriculture Vels Institute of Science, Technology and Advanced Studies (VISTAS) Pallavaram, Chennai - 600 117
- 2. Global Positioning System (GPS) is a satellite-based navigation system that provides accurate location data (latitude, longitude, and altitude) anywhere on Earth. In precision farming, GPS plays a pivotal role by enabling precise field mapping, accurate navigation of farm machinery, and efficient management of agricultural inputs. GPS allows for the automation and optimization of various farming processes, leading to increased productivity, reduced costs, and improved sustainability. GPS
- 3. Positioning: Determining the precise location on Earth Navigation: Providing route guidance and direction Timing: Delivering accurate time data for synchronization Mapping and Monitoring: Supporting geographical data collection and analysis Four Primary Functions of GPS
- 4. Componentsof GPS Space Segment (Satellites) Space segment refers to the network of satellites orbiting the Earth that transmit signals to GPS receivers on the ground. Current GPS system consists of a constellation of at least 24 satellites (operating in medium Earth orbit), which continuously transmit signals with time and position information. GPS satellites provide the necessary positioning information to GPS receivers on farm equipment, enabling accurate field navigation, mapping, and tracking of farm operations.
- 5. Components of GPS Control Segment (Ground Control Stations) Control segment comprises of a master control station and five monitor stations Control segment consists of ground-based control stations (master control station) and five monitor stations control the GPS satellites' positions and signal integrity. These stations track the satellites' positions and make adjustments to ensure their accuracy and proper functioning. Control segment ensures the continued reliability and accuracy of the GPS system, which is essential for precise farming operations, such as auto- guidance systems, field mapping, and variable rate technology Control segment also referred as monitor station
- 6. Interconnection: • The space segment provides signals, the control segment ensures signal accuracy, and the user segment interprets the signals to deliver positioning information. Together, they make GPS a highly reliable global navigation system. Components of GPS User Segment (Receivers and Equipment) User segment consists of GPS receivers installed on farm equipment such as tractors, combines, harvesters, and sprayers. These receivers pick up the signals transmitted by the GPS satellites and calculate the precise location of the equipment in real-time. GPS receivers on farming machinery interpret satellite signals and provide accurate location data, allowing for the automation and precise control of farm equipment. This is crucial for tasks such as field mapping, auto-steering, and variable rate applications.
- 8. GPS Working Procedure Satellites Transmit Signals: GPS satellites orbit the Earth and constantly broadcast signals containing their location and the time the signal was sent. Receiver Captures Signals: A GPS receiver picks up signals from at least four satellites. Triangulation: The receiver calculates the distance to each satellite based on the time it took for the signals to arrive. Position Calculation: Using data from multiple satellites, the receiver determines its precise location (latitude, longitude, and altitude) through trilateration. This process happens in real-time, providing accurate positioning, navigation, and timing for various applications like navigation, mapping, and geolocation services.
- 9. GPS Errors GPS Errors are inaccuracies in positioning caused by various factors affecting satellite signals and receiver performance. 1. Satellite Clock Errors: Inaccuracies in the atomic clock onboard GPS satellites can lead to errors in time synchronization, impacting distance calculations. 2. Orbital Errors (Ephemeris Errors): Slight inaccuracies in the satellite's reported position can lead to errors in the user's position calculation. 3. Atmospheric Delays: Ionosphere: Signal delays caused by charged particles in the ionosphere. Troposphere: Signal bending or slowing due to water vapor and air density. 4. Multipath Errors: Occurs when GPS signals reflect off surfaces like buildings or water before reaching the receiver, causing distorted readings. 5. Receiver Noise and Antenna Errors: Internal noise or hardware imperfections in the GPS receiver can degrade signal processing and accuracy. 6. Selective Availability (Historical): Previously, intentional errors were introduced for security (discontinued in 2000 for civilian use).
- 10. GPS Errors 7. Satellite Geometry (GDOP): Poor satellite geometry (e.g., clustered satellites) reduces positioning accuracy, measured by GDOP (Geometric Dilution of Precision). 8. Signal Obstructions: Physical obstructions like buildings, trees, and mountains can block or weaken satellite signals. 9. Human or Software Errors: Errors in data processing, coordinate systems, or input/output operations can affect results. 10. Relativity Effects: Time dilation due to the satellite's high speed and gravitational field differences causes minor errors, corrected by GPS systems. Mitigation Techniques: Differential GPS (DGPS): Corrects errors using ground-based reference stations. SBAS (Satellite-Based Augmentation Systems): Provides additional corrections. Improved Receivers: Modern GPS devices have better algorithms to handle errors. Multi-frequency Signals: Using multiple frequencies helps reduce atmospheric delay errors.
- 11. Differential GPS (DGPS) Differential GPS (DGPS) is an enhanced version of the Global Positioning System (GPS) that improves location accuracy by using correction signals. Reference Station: A ground-based reference station is set up at a known, fixed location. It receives GPS signals just like any regular GPS receiver. Error Calculation: The reference station compares the satellite signal's expected position (known location) with the position determined by the GPS signals, calculating the error caused by factors like atmospheric conditions or satellite clock drift. Correction Signal: The station broadcasts this calculated error as a correction signal to nearby GPS receivers via radio or internet. Improved Accuracy: The GPS receivers apply these corrections to their own calculations, significantly improving their positional accuracy (up to a few centimeters).
- 12. Navstar GPS Navstar GPS (Navigation Satellite Timing and Ranging - Global Positioning System) is a satellite-based navigation system developed and maintained by the United States Air Force (USAF). It provides accurate positioning, navigation, and timing (PNT) services worldwide. Key Features: Satellite Constellation: Operates with a minimum of 24 satellites in medium Earth orbit (MEO). Satellites are arranged in six orbital planes, ensuring global coverage. Global Coverage: Provides continuous, real-time location and time data across the globe.
- 13. Navstar GPS Dual-Use System: Military Applications: Used for precision targeting, navigation, and secure communications in defense operations. Civilian Applications: Open for public use in fields like transportation, mapping, agriculture, and telecommunications. Management: The system is operated by the United States Space Force, with the USAF initially developing and launching the satellites.
- 14. Navstar GPS Operation: The satellites transmit coded signals containing precise timing and location data. Ground control stations monitor and manage satellite orbits and system health. User receivers calculate their position by processing signals from at least four satellites using trilateration. Advantages: High reliability and robustness for both military and civilian use. Backbone of modern navigation systems globally. Historical Significance: Navstar GPS was conceived in the 1970s, became fully operational in 1993, and remains a critical component of global navigation and timing infrastructure
- 15. GPS Satellite Geometry GPS Satellite Geometry refers to the spatial arrangement of GPS satellites relative to a receiver. It significantly affects the accuracy of positioning measurements. Key Concepts: Good Geometry: Satellites are well-distributed across the sky. Provides high positional accuracy because signals arrive from diverse angles, reducing errors during trilateration. Poor Geometry: Satellites are clustered or aligned closely together (e.g., all overhead or along a single line). Reduces accuracy as the positional calculations have higher uncertainty. Geometric Dilution of Precision (GDOP): A measure of how satellite geometry affects accuracy. Lower GDOP values indicate better satellite geometry and higher accuracy. GDOP is categorized into: PDOP (Position Dilution of Precision): Related to 3D positioning accuracy. HDOP (Horizontal Dilution of Precision): Accuracy of latitude and longitude. VDOP (Vertical Dilution of Precision): Accuracy of altitude.
- 16. GPS Satellite Geometry Optimal Satellite Geometry: Ideally, satellites should be spaced evenly, with some overhead and others near the horizon. Requires signals from at least four satellites for accurate 3D positioning (latitude, longitude, and altitude). Challenges: Obstructions (buildings, trees) can block signals, leading to poor geometry. Atmospheric interference may degrade signal quality even with good geometry. Importance: GPS satellite geometry plays a critical role in applications where precise location is essential, such as surveying, aviation, and autonomous navigation. Understanding and monitoring geometry help optimize accuracy and reliability.
- 17. Key applications of GPS in agriculture Precision Farming: Guides machinery for precise planting, fertilizing, and spraying, reducing waste and improving efficiency. Field Mapping: Creates accurate field maps to analyze soil types, crop health, and topography for better planning. Yield Monitoring: Tracks yield variations across fields, helping farmers identify high and low- performing areas. Variable Rate Technology (VRT): Enables site-specific application of inputs like seeds, fertilizers, and pesticides, optimizing resource use. Auto-Guidance Systems: Assists tractors and harvesters with automatic steering for straight and consistent rows, even in low visibility. Irrigation Management: Integrates with sensors to monitor moisture levels and optimize irrigation patterns. Pest and Disease Monitoring: Maps and identifies pest-affected areas for targeted treatments, minimizing crop loss
- 18. Functions of GPS in Precision Farming Field Mapping GPS allows farmers to create highly accurate maps of their fields, which are essential for understanding field variability. This includes mapping soil properties, crop yield, elevation, moisture levels, and more. Maps help farmers identify areas within a field that need specific attention (e.g., areas with low yield or nutrient deficiencies), enabling them to apply inputs more precisely
- 19. Functions of GPS in Precision Farming Auto-Steering and Guidance Systems GPS-enabled auto-guidance systems allow tractors, harvesters, sprayers, and other farm machinery to navigate fields autonomously with high precision. Auto-steering systems adjust the machinery’s steering automatically to follow a predetermined path based on GPS coordinates. This reduces overlap and gaps during field operations, ensuring that resources like seeds, fertilizers, and pesticides are applied with maximum efficiency. It also reduces fuel consumption and the need for manual labor, improving both cost-effectiveness and productivity.
- 20. Functions of GPS in Precision Farming Variable Rate Technology (VRT) GPS enables variable rate technology, which allows for the precise application of inputs (fertilizers, seeds, pesticides, water, etc.) at variable rates across a field, based on real-time data from GPS and other sensors. With GPS, farmers can apply different rates of fertilizers or pesticides depending on the soil conditions or crop needs in different parts of a field, leading to better resource utilization, higher yields, and reduced environmental impact E.g., by avoiding over-application of fertilizers or pesticides
- 21. Functions of GPS in Precision Farming Yield Mapping and Monitoring GPS technology integrated with yield monitors (installed on harvesters) allows for real-time tracking of crop yield across a field during harvest. GPS receiver records the location of the harvester, and the yield monitor tracks the crop yield. Data from yield monitors combined with GPS coordinates is used to create yield maps, which provide farmers with insights into the variability of crop production across different parts of the field. This helps farmers make better decisions for future crop management and field input applications
- 22. Functions of GPS in Precision Farming Guided Spraying GPS technology is used in precision spraying systems to guide sprayers across the field, ensuring that pesticides, herbicides, or fertilizers are applied in specific, targeted areas. GPS ensures that the sprayer follows an optimal path and that no area is left unsprayed or over-sprayed. This reduces the amount of chemicals used, minimizing waste and environmental impact while maintaining effective pest and weed control
- 23. Functions of GPS in Precision Farming Precision Irrigation GPS is used in conjunction with soil moisture sensors and weather data to guide irrigation systems, ensuring that water is applied precisely where and when it is needed. GPS coordinates help ensure that irrigation systems cover the correct areas of a field. This optimizes water use, reduces waste, and ensures that crops receive the appropriate amount of water for healthy growth. It is especially important in areas facing water scarcity.