Geographic Information Geographic Information SystemsSystems

GIS Data - Remote SensingGIS Data - Remote Sensing

Remote Sensing DefinitionRemote Sensing Definition

"I want to know how God created this world. I am not interested in this or that phenomenon, in the spectrum of this or that element. I want to know His thoughts; -the rest are details.“ Albert Einstein

Remote Sensing Remote Sensing Definition ..Definition ..

► The technique of collecting The technique of collecting information from a distance without information from a distance without physical touchphysical touch

► Remotely sensed dataRemotely sensed data

Aerial photographyAerial photography

Digital satellite imagesDigital satellite images

Radar imagesRadar images

etc. etc.

2. Properties of EM Energy2. Properties of EM Energy ► EM travels at the speed of light EM travels at the speed of light 3x103x1088m/secm/sec

► Wavelength Wavelength and Frequency and Frequency

Properties .. Properties .. ► The type of energy is defined by The type of energy is defined by its position in the EM spectrum in its position in the EM spectrum in terms of wavelength, measured byterms of wavelength, measured bymm

► 1m = 1,000mm, 1mm = 1,0001m = 1,000mm, 1mm = 1,000mm

http://kr.blog.yahoo.com/bmw26z/2188

Properties ..Properties ..

► Major divisions of EM spectrumMajor divisions of EM spectrum► X-rays, UV, visible, infrared, X-rays, UV, visible, infrared, microwave, TVmicrowave, TV

http://csep10.phys.utk.edu/astr162/lect/light/spectrum.html

Properties ..Properties ..

From http://rst.gsfc.nasa.gov/Intro/nicktutor_I-From http://rst.gsfc.nasa.gov/Intro/nicktutor_I-3.html3.html

► Atmospheric effectsAtmospheric effects► Atmospheric absorption: HAtmospheric absorption: H22O, COO, CO22, O, O33

Properties ..Properties ..

http://www.crisp.nus.edu.sg/~research/tutorial/atmoseff.htm#windows

► Atmospheric windowsAtmospheric windows

Those wavelengths that are Those wavelengths that are relatively easily transmitted relatively easily transmitted through the atmospherethrough the atmosphere

► The windows: UV, visible, near The windows: UV, visible, near infrared, mid infrared, far infrared, mid infrared, far infrared, microwaveinfrared, microwave

Properties ..Properties ..

► Atmospheric scatteringAtmospheric scattering

The redirection of EM energy by The redirection of EM energy by particles suspended in the particles suspended in the atmosphere or large molecules of atmosphere or large molecules of atmospheric gasesatmospheric gases

► Radiation of short wavelength is Radiation of short wavelength is easier to be scatteredeasier to be scattered

http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/opt/mch/sct.rxml

Properties .. Properties ..

►   Responses of features on earth to EM Responses of features on earth to EM energyenergy

Reflection (%), transmission (%), and Reflection (%), transmission (%), and absorption (%)absorption (%)

Reflection + Transmission + Absorption = Reflection + Transmission + Absorption = 100%100%

Reflection

Absorption Transmission

Properties ..Properties ..

► ReflectionReflection

- Light ray is redirected as it - Light ray is redirected as it strikes a nontransparent surfacestrikes a nontransparent surface

Properties ..Properties ..Reflection

Properties ..Properties ..

► TransmissionTransmission

Radiation passes through a substance Radiation passes through a substance without significant attenuation without significant attenuation

► Transmittance (t): Transmittance (t):                   transmitted                   transmitted radiation radiation            t            t =  ---------------------------=  ---------------------------                    incident radiation                    incident radiation

PropertiesProperties

http://www.crisp.nus.edu.sg/~research/tutorial/infrared.htm

Absorption and emission

3. Major Sensor Systems3. Major Sensor Systems

► Aerial photography Aerial photography ► Electro-Optical remote sensing Electro-Optical remote sensing ► Microwave remote sensingMicrowave remote sensing

3 (1) Aerial Photography3 (1) Aerial Photography

► Photographic cameras Photographic cameras ► Uses aerial cameras and filmUses aerial cameras and film► Mounted on an aircraftMounted on an aircraft► Produces aerial photographsProduces aerial photographs

3 (2) Electro-Optical 3 (2) Electro-Optical Remote SensingRemote Sensing

► Electro-Optical scannersElectro-Optical scanners► Uses light-sensitive detectorsUses light-sensitive detectors► Mounted on spacecrafts or aircraftsMounted on spacecrafts or aircrafts ► Generates digital imagesGenerates digital images

http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=4396

Buffalo, NY November 20, 2000

http://www.esri.com/news/pressroom/hurricanemaps.html

Biloxi Coast–Before Hurricane Katrina, April 12, 2005

Biloxi Coast–After Hurricane Katrina, August 31, 2005.

3 (3) Microwave Remote 3 (3) Microwave Remote SensingSensing

► Uses antennas as Uses antennas as detectorsdetectors

► Passive microwave Passive microwave systems systems

► Active microwave Active microwave systems, RADARsystems, RADAR

http://www.erh.noaa.gov/buf/

http://rst.gsfc.nasa.gov/Sect8/Sect8_3.html

4. Operation of Digital 4. Operation of Digital Remote SensingRemote Sensing

► Moving mirror and pushbroomMoving mirror and pushbroom

Operation ..Operation ..

Pixel and IFOV Pixel and IFOV ► Pixel - picture Pixel - picture elementelement

► IFOV - IFOV - Instantaneous Field Instantaneous Field of View - The of View - The ground area viewed ground area viewed by the sensor at a by the sensor at a given instantgiven instant

Operation ..Operation ..

► Sensors and detectorsSensors and detectors► Each sensor system contains a set of Each sensor system contains a set of detectors, each set is sensitive to a detectors, each set is sensitive to a certain range of wavelength (band)certain range of wavelength (band)

► Detectors of each band produce a digital Detectors of each band produce a digital image, which is a matrix consisting of image, which is a matrix consisting of rows and columns of pixelsrows and columns of pixels

► The digital number of each pixel measures The digital number of each pixel measures the intensity of energy received from the the intensity of energy received from the IFOV area on the groundIFOV area on the ground

► Images of several bands result in a Images of several bands result in a composite imagecomposite image

Operation ..Operation ..

Green Red Near Infrared NIR

OperationOperation

► True and false color composite imagesTrue and false color composite images

5. Types of Resolution5. Types of Resolution

► Spectral resolution Spectral resolution ► Radiometric resolution Radiometric resolution ► Spatial resolution Spatial resolution ► Temporal resolutionTemporal resolution

5(1) Spectral Resolution5(1) Spectral Resolution

► The dimension and the number of The dimension and the number of specific wavelength intervals in the specific wavelength intervals in the EM spectrum to which a sensor is EM spectrum to which a sensor is sensitive to, e.g. B, G, R, NIR sensitive to, e.g. B, G, R, NIR bandsbands

Green Red Near Infrared NIR

5(2) Spatial Resolution5(2) Spatial Resolution

► A measure of the smallest angular or A measure of the smallest angular or linear separation between two objects linear separation between two objects that can be revolved by the sensor, that can be revolved by the sensor, 30m, 1m, 1km30m, 1m, 1km

10m 20m 40m 80m

5(3) Radiometric Resolution5(3) Radiometric Resolution

► The sensitivity of a detector to The sensitivity of a detector to differences in signal strength as it differences in signal strength as it records the radiant levelsrecords the radiant levels

2 levels 4 levels 16 levels 256 levels

1 bit 2 bit 4 bit 8 bit

5(4) Temporal Resolution5(4) Temporal Resolution

► How often a given sensor obtains How often a given sensor obtains imagery of a particular area, e.g., imagery of a particular area, e.g., 16 days, daily16 days, daily

6. Commonly Used Satellite 6. Commonly Used Satellite Image DataImage Data

► Moderate resolution land satellitesModerate resolution land satellites

LandsatLandsat SPOTSPOT

Landsat 5, New Yorkhttp://landsat.gsfc.nasa.gov/images/gallery.html

6. Commonly Used Satellite 6. Commonly Used Satellite Image DataImage Data

► High resolution land High resolution land satellitessatellites

► IKONOSIKONOS► OrbviewOrbview► GeoEyeGeoEye► QuickBirdQuickBird

IKONOS images: Washington DC, Hoover Dam, Hollywood

6. Commonly Used Satellite 6. Commonly Used Satellite Image Data ..Image Data ..

► Meteorological Meteorological satellitessatellites

► AVHRRAVHRR► EOSEOS

Sea surface temperature in hurricane alley. This false color composite image is made using data taken by AMSR-E on board EOS, May 2002.

AVHRR

6. Commonly Used Satellite 6. Commonly Used Satellite Image Data ..Image Data ..

► Radar systemsRadar systems► RADARSETRADARSET► LIDARLIDAR

RADARSET

Courtesy of EarthData Technologies

LIDAR

6. Commonly Used Satellite 6. Commonly Used Satellite Image Data ..Image Data ..

► Digital aerial Digital aerial photographs photographs

► DOQQDOQQ

LIDAR

ReadingsReadings

► Chapter 8Chapter 8