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Chapter 5 Remote Sensing

Chapter 5 Remote Sensing. Crop Science 6 Fall 2004 October 22, 2004. Remote Sensing. A group of techniques for collecting information about an object or an area without being in physical contact with that object or area Started in the 30’s Most common RS Aircraft-based Satellite-based.

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Chapter 5 Remote Sensing

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  1. Chapter 5Remote Sensing Crop Science 6 Fall 2004 October 22, 2004

  2. Remote Sensing • A group of techniques for collecting information about an object or an area without being in physical contact with that object or area • Started in the 30’s • Most common RS • Aircraft-based • Satellite-based

  3. The measurement of energy that is reflected or emitted from objects Electromagnetic energy travels as waves Electromagnetic Spectrum (shortest wavelength to longest) Ultraviolet (UV) Visible Near Infrared Thermal Infrared Far Infrared Microwave VHF HF Basics

  4. For Ag we focus on the bands Ultraviolet (UV) Visible Near Infrared Thermal Infrared Far Infrared Wavelengths of color (um) Violet - 0.4 Blue – 0.5 Green – 0.55 Yellow – 0.58 Orange – 0.6 Red – 0.7 Basics

  5. Interaction • Electromagnetic energy strikes an object and is • Reflected • Emitted • Absorbed • Remote sensing measures the reflected and emitted energy • Green plants look green because • Green Wavelengths are reflected • Blue and Red wavelengths are absorbed

  6. Interaction • Factors affecting reflected light • Height of sun above the horizon • Blue light is scattered more • Ozone layer absorbs most UV • Shadowing • Reduction of light hitting an object from clouds • Air temperature affects reflected or emitted energy

  7. Measures of Performance • Spatial Resolution • Size of smallest object that can be distinguished • Spectral Response • Respond to radiation measurements within a spectral band • Spectral Resolution • Differentiate between electromagnetic radiation at different wavelengths • Temporal Resolution • Frequency of Coverage

  8. Characteristics • Electro-optical sensors are • Light sensitive • Create electrical signal proportional to the amount of energy that hits them • Rotating mirrors and lenses • Allow one sensor to “see” different spots on the ground • Scanning • Collecting data from parallel paths • Perpendicular to the flight path • Array • Line of optical sensors • Whole swath is sensed at once

  9. Use of RS Data • Vegetation Indices • Predict and assess plant leaf area and plant stress • As chlorophyll changes so do reflected wavelengths • Red Edge • Wavelengths from 0.68-0.75 um • Area of sharp changes in reflectance

  10. Image Correction • Radiometric Correction • Fog or haze • Sensor viewing angles • Image processing procedure • Geometric Correction (Geo-rectified) • Earth rotation • Satellite Motion • Uses ground control points

  11. Satellite-based RS • Four major sources • LANDSAT • SPOT • Space Imaging (IKONOS) • Digital Globe (Quick Bird)

  12. Economic Considerations • Cost varies by • Image type • Image size • Level of processing • Timeliness • Spatial resolution

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