EG1106geographic information: a primer

Introduction to remote sensing24th November 2004

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)

Types of platform

AircraftSatelliteBalloonRocketOrbiting spacecraft

Most common is the satellite

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

Geostationary Polar 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 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

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 monitoringCommercial agriculturePetrochemicalHealthHydrology and geologyPollution monitoringClimate change

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!!