eg1106 geographic information: a primer introduction to remote sensing 24 th november 2004
TRANSCRIPT
TOPICS
What is remote sensing?The electromagnetic spectrumTypes of platformSatellite remote sensing in detailProxy variables produced by RSApplications of remote sensingPractical feedback today - reminder!
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
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
Physical Objects
Sensor Data
Extracted Information
Applications
Land use Geology Hydrology Vegetation Soils Human Health
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
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
Radiation from the Sun has a short wavelength (shortwave). Radiation from the Earth has a long wavelength (longwave)
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
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
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
Proxy variables produced by RSTemperature
from radiance measurements (TIR)
RainfallFrom Cold Cloud Duration (TIR)
Wind speedFrom analysis of water vapour (WV)
HumidityTropospheric data (WV)
Proxy variables produced by RSVegetation
NDVI (RED and NIR)
AlbedoReflectance in visible region of ES
Applications of RS
Environmental monitoringCommercial agriculturePetrochemicalHealthHydrology and geologyPollution monitoringClimate change