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 Practical 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 s: Rapid development of digital image processing and launch of high resolution satellite sensors

Physical Objects Sensor Data Extracted Information Applications Land useGeologyHydrologyVegetationSoilsHuman Health

The electromagnetic spectrum All objects above absolute zero ( ºC or 0ºK) emit electromagnetic radiation ER is produced by mechanisms such as: Changes in energy levels of electrons Acceleration of electrical charges Radioactive decay Thermal 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 spectrum Some 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)

Types of platform Aircraft Satellite Balloon Rocket Orbiting spacecraft Most common is the satellite

Satellite remote sensing in detail Orbiting satellites have different strategies according to their purpose Polar orbiters provide high resolution imagery for local studies Geostationary satellites provide high temporal resolution for large area studies

Satellite remote sensing in detail GEOSTATIONARYPOLAR ORBITER Updates every hourupdates twice a day Low spatial resolutionHigh spatial resolution Used for weather predictionUsed for monitoring Sees only portion of EarthGlobal coverage

GeostationaryPolar Orbiter

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 RS Temperature from radiance measurements (TIR) Rainfall From Cold Cloud Duration (TIR) Wind speed From analysis of water vapour (WV) Humidity Tropospheric data (WV)

Proxy variables produced by RS Vegetation NDVI (RED and NIR) Albedo Reflectance in visible region of ES

AVHRR 29/11/01 13:39 < VIS IR >

Meteosat: 29/11/2001 at 12:00z

Aerial photograph: Liverpool docks area

Landsat Thematic Mapper (TM): Liverpool

Applications of RS Environmental monitoring Commercial agriculture Petrochemical Health Hydrology and geology Pollution monitoring Climate change

Practical Feedback Today Groups A2, B1 & B22 – 3:30pm Groups A1, C1 & C23:30 - 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!!