eg1106 geographic information: a primer
DESCRIPTION
EG1106 geographic information: a primer. Introduction to remote sensing 24 th November 2004. TOPICS. What is remote sensing? The electromagnetic spectrum Types of platform Satellite remote sensing in detail Proxy variables produced by RS Applications of remote sensing - PowerPoint PPT PresentationTRANSCRIPT
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EG1106geographic information: a primer
Introduction to remote sensing24th November 2004
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TOPICS
What is remote sensing?The electromagnetic spectrumTypes of platformSatellite remote sensing in detailProxy variables produced by RSApplications of remote sensingPractical feedback today - reminder!
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What is Remote Sensing?
A Definition:
Remote sensing is the practice of deriving information about the earth’s land and water surfaces using images acquired from an overhead perspective, using electromagnetic radiation in one or more regions of the electromagnetic spectrum, reflected or emitted from the earth’s surface.
Campbell, 1996
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What is Remote Sensing?Milestones in RS history:
1800: Discovery of infrared by Sir William Herschel
1839: Beginnings of photography
1850: Aerial photography using balloons
1909: Photography from aircraft
1972: Launch of Landsat
1970s - 1990s: Rapid development of digital image processing
and launch of high resolution satellite sensors
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Physical Objects
Sensor Data
Extracted Information
Applications
Land use Geology Hydrology Vegetation Soils Human Health
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The electromagnetic spectrum
All objects above absolute zero (-273.15ºC or 0ºK) emit electromagnetic radiationER is produced by mechanisms such as:
Changes in energy levels of electronsAcceleration of electrical chargesRadioactive decayThermal motion of atoms and molecules
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The electromagnetic spectrum
Nuclear reactions occur within the Sun which emits ER across a broad range of wavelengths called a spectrumSome regions of this spectrum are visible (visible light) and some are invisible (infrared or ultraviolet)Remote sensing relies on the measurement of this radiation
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Radiation from the Sun has a short wavelength (shortwave). Radiation from the Earth has a long wavelength (longwave)
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Types of platform
AircraftSatelliteBalloonRocketOrbiting spacecraft
Most common is the satellite
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Satellite remote sensing in detail
Orbiting satellites have different strategies according to their purposePolar orbiters provide high resolution imagery for local studiesGeostationary satellites provide high temporal resolution for large area studies
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Satellite remote sensing in detail
GEOSTATIONARY POLAR ORBITER
Updates every hour updates twice a day
Low spatial resolution High spatial resolution
Used for weather prediction Used for monitoring
Sees only portion of Earth Global coverage
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Geostationary Polar Orbiter
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Proxy variables produced by RS
RS produces continuous surface information (a raster layer within GIS)Environmental variables may be derived from satellite information - but we call these proxies of the variable as they are only inferred from radiation measurements
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Proxy variables produced by RSTemperature
from radiance measurements (TIR)
RainfallFrom Cold Cloud Duration (TIR)
Wind speedFrom analysis of water vapour (WV)
HumidityTropospheric data (WV)
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Proxy variables produced by RSVegetation
NDVI (RED and NIR)
AlbedoReflectance in visible region of ES
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AVHRR
29/11/01
13:39
< VIS
IR >
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Meteosat: 29/11/2001 at 12:00z
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Aerial photograph: Liverpool docks area
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Landsat Thematic Mapper (TM): Liverpool
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Applications of RS
Environmental monitoringCommercial agriculturePetrochemicalHealthHydrology and geologyPollution monitoringClimate change
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Practical Feedback Today
Groups A2, B1 & B2 2 – 3:30pmGroups A1, C1 & C2 3:30 - 5pm
NOTE: Bring ALL three pracs for marking & return
Next week will be D1, D2, E1 & E2 ONLY
These are the FINAL practical sessions for this term!!