CS 128/ES Lecture 9a1 Principles of Remote Sensing Image from NASA – Goddard Space Flight Center, NOAA GOES-8 satellite, 2 Sep ’94, 1800 UT

CS 128/ES Lecture 9a2 Scanning planet Earth from space

CS 128/ES Lecture 9a3 History of remote sensing Earliest vehicle was …? Tournachon (‘Nadar’) took 1 st aerial photograph in 1858 (since lost) Earliest conserved aerial photograph: Boston, J. Black, 1860 Early applications were in military reconnaissance

CS 128/ES Lecture 9a4 WWII – heavy use of aerial reconnaissance Images: Avery Interpretation of Aerial Photographs. 3rd ed. Burgess Press, Minneapolis, MN.

CS 128/ES Lecture 9a5 “Spy planes” & the Cold War

CS 128/ES Lecture 9a6 Satellite sensing Russian Sputnik (1957) - radio transmitter only Rapid response by US: CORONA (1960) Early applications: military reconnaissance

CS 128/ES Lecture 9a7 Advantages of satellites Wide coverage Vertical (orthogonal) view Multi-spectral data bands Rapid data collection

CS 128/ES Lecture 9a8 Sources of EM radiation Key distinction: passive sensing active sensing Spectral ‘signatures” Top: Lo & Yeung, fig. 8.1 Bottom: ASTER Spectral Library (

CS 128/ES Lecture 9a9 Types of EM radiation used Three important spectral bands: visible light infrared radiation microwave radiation Image from NASA SAR: Synthetic Aperture Radar. Earth Observing System, Vol. IIf.

CS 128/ES Lecture 9a10 Atmospheric attenuation Scattering caused by aerosols (water vapor, dust, smoke) more intense at shorter wavelengths why the sky is blue Absorption  caused by gas molecules (H 2 O, CO 2, O 2, O 3 )  each molecule absorbs at a specific wave- length  result: atmospheric transmission windows

CS 128/ES Lecture 9a11 Transmission windows  UV-visible-IR  Microwave Image from NASA From Pattern to Process: The Strategy of the Earth Observing System. Vol. II.

CS 128/ES Lecture 9a12 Classes of sensors Photographic panchromatic color Infrared (IR)  film (near IR)  thermal IR sensors for longer wave- lengths Multi-spectral scanners  sensors for many wavelengths  image scanned across sensors Radar  RAdio Detection And Ranging  active imaging

CS 128/ES Lecture 9a13 Visual sensors: film types panchromatic near-infrared color Both images from Committee on Earth Observation Satellites

CS 128/ES Lecture 9a14 Infrared sensors  IR penetrates haze and light cloud cover can be used at night used by military for camouflage detection IR ‘signature’ often distinct from visible image

CS 128/ES Lecture 9a15 Color IR film  Used with yellow (blue- absorbing) filter 3 primary pigments, but not “true” (visible) color - green vegetation = red - clear water = dark blue - turbid water = bright blue - soil = green - urban areas = pale blue Top image: Committee on Earth Observation Satellites Bottom image: Avery Interpretation of Aerial Photographs. 3 rd ed. Burgess Press, Minneapolis, MN.

CS 128/ES Lecture 9a16 Multispectral sensors Visible + IR spectra Comparison of film and electronic sensor spectral bands Top: Avery Interpretation of Aerial Photography. Burgess Publ., Ninneapolis Bottom: ASTER Science page (

CS 128/ES Lecture 9a17 Radar sensors active sensing day & night, all weather less affected by scattering (aerosols) vertical or oblique perspective Lo & Yeung, fig. 8.13

CS 128/ES Lecture 9a18 Uses of radar: altimetry satellite-nadir distance geoid & topographic measurements sea elevation, tides & currents wave/storm measurements Both images from NASA Altimetric System. Earth Observing System, Vol. IIh.

CS 128/ES Lecture 9a19 Uses of radar: SAR glaciology hydrology vegetation science geology Image from NASA SAR: Synthetic Aperture Radar. Earth Observing System, Vol. IIf.

CS 128/ES Lecture 9a20 Sensor resolution Spatial: size of smallest objects visible on ground. Ranges from 1 km. Inversely related to area covered by image Spectral: wavelengths recorded. Ex. panchromatic film (~0.2 – 0.7 µm); Landsat Thematic Mapper bands (0.06 to 0.24 µm wide) Radiometric: # bits/pixel. Ex. Landsat TM (8 bit); AVRIS (12 bit) Temporal: for satellite, time to repeat coverage. Ex. Landsats 5 & 7 (16 days)

CS 128/ES Lecture 9a21 Spatial resolution: analog (film) images Depends on: lens quality & camera stability size of negative film grain High quality aerial photograph:  up to 60 lines/mm  9 x 9” (23 x 23 cm) negative  scanned at 3000 dpi = ~725 megapixels  if 8 bit image depth, >5 GB image size

CS 128/ES Lecture 9a22 Ground resolution G. R. = scale factor / film resolution Focal length of lens (mm) Altitude of plane (m) Scale of photograph Ground resolution (m) :3, ,0001:35, ,0001:54,

CS 128/ES Lecture 9a23 Spatial resolution: digital (satellite) images A sampler of recent (civilian) satellites: SponsorSatellite (instrument)YearRes. (m) NASALandsat (Thematic Mapper) s30 (MSS) NASA & others EOS Terra (ASTER) (MSS) FranceSPOT-3 to to 5 (pan) Space Imaging IKONOS (pan) 4 (MSS) EarthWatchQuickbird (pan) 2.5 (MSS)

CS 128/ES Lecture 9a24 Satellite image resolution Quickbird 2 Commercial venture 0.63 m resolution U.S. trying to discourage open access to finer resolution images Digitalglobe.com

CS 128/ES Lecture 9a25 Satellite orbits Geostationary 36,000 km above equator Polar varying heights often in Sun- synchronous orbits Both diagrams from European Organisation for the Exploitation of Meteorological Satellites

CS 128/ES Lecture 9a26 Satellite coverage Geostationary no polar coverage coverage is 24/7 low ground reso- lution (~ 1 km) Polar global coverage coverage is dis- continuous Both diagrams from European Organisation for the Exploitation of Meteorological Satellites

CS 128/ES Lecture 9a27 Geostationary orbits Ex. GOES satellites Meteorological satellites GOES-8 at 75 o W, GOES-9 at 135 o W 5 bands (1 visible, 4 thermal infrared) Image from NASA – Goddard Space Flight Center, NOAA GOES satellite, Hurricane Floyd, 15 Sep ‘99

CS 128/ES Lecture 9a28 Polar orbits Ex. Landsat & Terra satellites 705 km height, ~100 minute orbit 185 km swath 16 day repeat Sun-synchronous orbits (~0945 a.m. equator crossing) Orbit tracking data from NASA – 5 Mar ‘03