Introduction to Remote Sensing

Introduction to Remote Sensing Daniel McInerney Urban Institute Ireland, University College Dublin, Richview Campus, Clonskeagh Drive, Dublin 14. 16th June 2009

Presentation Outline 1 2 Spaceborne Sensors Sensor Characteristics 3 Low Resolution Data Medium Resolution Data High Resolution Data

of lecture To provide a basic introduction to remote sensing Demonstrate some types of remote sensing data Quick RS exercise using ArcGIS 9.3

What is a Remote Sensing? Simply put it is the measurement of objects/targets from a distance Definitions... the measurement from a distance, of the spectral features of the Earth s surface and atmosphere. (Mather, 1999).... the use of electromagnetic radiation sensors to record images of the environment which can be interpreted to yield useful information. (Curran, 1985).

Principal benefits of remote sensing major role in observation simultaneous monitoring with great detail and uniformity

Physical basis of Remote Sensing Source - electromagnetic radiation (Sun) Interaction with the Earthś surface - amount of radiation reflected depends on object Interaction with the atmosphere distorts and scatters light (interference) Sensor to record

Electromagnetic Radiation EMR waves transported through space at the speed of light (c = 299,792,458 m/s) EMR spectrum can be divided into several wavelengths (frequency) regions visible spectrum is 400-700 nm No sharp boundaries between these regions

EMR Spectrum

Beyond the visible spectrum Infrared light (700 nm - 1mm) Mid Infrared (1100 3000nm) Thermal (3000 1mm [heat]) Microwave radiation (1mm 300cm) Penetrates cloud

Interactions with the Earth s surface Incident radiation interference Transmission Reflection Scattering Absorption

Specific combination of reflected & absorbed EMR at varying wavelengths Reflectance from objects differs due to object types mineral / organic roughness and structure moisture content Distinct spectral signatures (spectral response) (vegetation, water, soils) Forms basis of discrimination/classification in optical remote sensing

- Landsat 7 ETM+

Definition Spaceborne Sensors Sensor Characteristics Definition Any optical system that scans the objects or image surface electromechanically or electronically in more than one wavelength Measure reflectance in atmospheric (windows) Passive and active sensors exist Record in digital format Orbiting Finite lifetimes Differ in a number of key characteristics

Spaceborne Sensors Sensor Characteristics Advantages of Spaceborne Remote Sensing Large area coverage Frequent and repetitive coverage of an area of interest; Quantitative measurement of ground features using radiometrically calibrated sensors; Semiautomated computerised processing and analysis; Relatively lower cost per unit area of coverage.

Characteristics Spaceborne Sensors Sensor Characteristics Swath width Spatial Resolution Spectral resolution Temporal resolution

Low Resolution Images Low Resolution Data Medium Resolution Data High Resolution Data NOAA-AVHRR SPOT-Vegetation SeaWIFS

AVHRR Low Resolution Data Medium Resolution Data High Resolution Data

Medium Resolution Images Low Resolution Data Medium Resolution Data High Resolution Data SPOT 4/5-XS Landsat TM/ETM+ AWiFS

Landsat 7 ETM+ Low Resolution Data Medium Resolution Data High Resolution Data

High Resolution Images Low Resolution Data Medium Resolution Data High Resolution Data Quickbird Ikonos Chris Proba

Ikonos Low Resolution Data Medium Resolution Data High Resolution Data

Conclusion Low Resolution Data Medium Resolution Data High Resolution Data Concluding remarks Remote Sensing is an important field in geo-science research Mainly used for environmental applications, but also in social science (r.f. population densities) Myriad of sensors available for different applications Questions, comments?