2 rWhat is remote sensing? rDevelopment of remote sensing rObservations of the Earths surface rCommunication and data collection systems rImage Processing rUse of remote sensing in geography
3 What is remote sensing? rRemote sensing is the acquisition of information about an object without physical contact. rIt includes photographic and digital remote sensors. rAircraft and satellites are major platforms for the sensors.
4 What is remote sensing? rObservation of a target by a device separated from it by some distance rWhat is measured? u lights or colour - to discuss later rHow are the photographs and images created rairborne and satellite data rHow can I use the images ridentifying things, interpretation, see the change
5 Remote sensing systems Reference data Pictorial Digital Visual Digital Sensing systems Data products Interpretation and analysis Information products Users
6 Development of remote sensing The term remote sensing was coined in the early 1960s by geographers in the Office of Naval Research of USA to apply to the information derived from photographic and non-photographic instruments.
7 Remote sensing prior to 1960 rAristotle (2300 years ago): camera obscura. r photographic process (Daguerre and Niepce) - daguerrotype. r first known balloon photograph (Tournachon - Nadar, France). rAir photograph - developed for military purposes. rBetween WW1 and WW2, civilian use of air photographs.
picture of Boston Harbour This 1860 picture of Boston Harbour is thought to be the first aerial photograph taken in the US. The exposure was made from a balloon at an altitude of about 365m above the ground
9 Old air-borne platforms Above: Stalwart pigeon photographers prepare to work. The tiny pigeon cameras were designed in 1903 and weighed about 70g. Right: Peering down a camera viewfinder from the open cockpit of a Curtiss Jenny, a flier practices the early techniques of aerial photography. (Courtesy Strain and Engle, 1992)
10 Airphoto – Hong Kong 1945
11 Remote sensing since 1960 r TIROS-I: the first meteorological satellite: low resolution sensor r ERTS-1 (changed to Landsat in 1975): MSS and HBV r NOAA: AVHRR r Landsat-4: TM r SPOT-1: PAN and XS rsince late 1980s: more earth observation satellites, e.g. Russian, Indian, Japanese, Chinese and others r1999: IKONOS commercial small satellites
: TIROS NASA/DOD
: ERTS 1 Return beam vidicon (RBV) cameras Data collection antenna Multispectral scanner (MSS) Solar array
: NOAA TIROS-N
: Landsat 4
: NOAA 8 Advanced TIROS-N (ATN)
: SPOT 1 SPOT - Système Pour lObservation de la Terre - initiated by French government in late 1970s. SPOT 1: 21/2/1986 SPOT 2: 21/1/1990 SPOT 3: 23/9/1993 SPOT 4: 26/3/1998 SPOT 5: 4/5/2002 All currently operational except SPOT 3, which is recently lost (1997).
18 Launched 1995 (Canada Space Agency) sun-synchronous, km orbit, repeat 24 days Sensor: C-band SAR 1995: Radarsat
19 Terra is the first of the NASAs Earth Observing System satellite series. It was launched in December 1999 and activated for science operation on 24 February Courtesy terra.nasa.gov 1999: EOS-AM 1 (Terra Spacecraft)
: IKONOS rThe first small satellite launched and operated by a commercial company (SpaceImaging) rWeight 1600 pounds rLaunched on 24 September 1999 rGround resolution: u Panchromatic: 1m u Multispectral: 4m
: QuickBird rCommercial remote sensing system developed and operated by DigitalGlobe rLaunched on 18 October 2001 rGround resolution: u Panchromatic: 61cm u Multispectral: 2.44m
22 Comparis on of the two major periods in the history of remote sensing
23 How does remote sensing work? rrecording and measuring electromagnetic radiation from the target. rThis recording and measurement can be taken by airborne or satellite sensors. rRemotely sensed images are rectified and enhanced to show information better. rWe interpret the images to get information on given locations for mapping, management, etc.
24 Observation of the earths surface rFor geographers, we use remote sensing to observe the Earths surface. rAir photographs offer detailed view of the Earths surface but limited by many factors. rSatellite photographs and images provide less detailed but more variety of information with a large and regular coverage.
25 Causes of differences in scale of aircraft and satellite observations Aircraft Satellite Thousands of metres Hundreds of kilometres
26 Passive and active remote sensing rPassive remote sensing: the sensor detects the reflectance of sunlight from the surface u e.g. photographs, multispectral scanners rActive remote sensing: the sensor detects the reflectance of the signal sent by the remote sensing system u e.g. RADAR
27 Passive remote sensing
28 Active remote sensing
29 Communication and data collection systems rRemotely sensed data has to be transmitted back to the Earth. rA network of satellite receiving stations have been established over the world to receive data. rSome satellite data can be directly received by small instruments. rData are available through variable commercial channels (e.g. EOSAT).
30 Overview of data collection and platform location system
31 Image processing rDigital images are the major types of todays remotely sensed data. rThey are fundamentally numbers. rTo make sense of them, a technology called image processing is employed to distort, enhance and extract information from the images. rImage processing and interpretation are the focus for this subject.
32 Use of remote sensing in geography rRemote sensing can bring us accurate, cheap and frequently updated information about the Earths surface. rGIS is the optimum tool to handle and integrate large amount of spatially referenced data including remotely sensed data. rMany things and phenomena in the real world are spatially referenced.
33 Some examples of applications rAgriculture rForestry rEnvironment rUrban and regional planning rMineral resources rand many more...