Principles of Remote Sensing Image from NASA Goddard

Principles of Remote Sensing Image from NASA – Goddard Space Flight Center, NOAA GOES-8 satellite, 2 Sep ’ 94, 1800 UT CS 128/ES 228 - Lecture 9 a 1

Scanning planet Earth from space CS 128/ES 228 - Lecture 9 a 2

History of remote sensing n Earliest vehicle was …? n Tournachon (‘Nadar’) took 1 st aerial photograph in 1858 (since lost) n Earliest conserved aerial photograph: Boston, J. Black, 1860 n Early applications were in military reconnaissance CS 128/ES 228 - Lecture 9 a 3

WWII – heavy use of aerial reconnaissance Images: Avery. 1977. Interpretation of Aerial Photographs. 3 rd ed. Burgess Press, Minneapolis, MN. CS 128/ES 228 - Lecture 9 a 4

“Spy planes” & the Cold War CS 128/ES 228 - Lecture 9 a 5

Satellite sensing n Russian Sputnik (1957) - radio transmitter only n Rapid response by US: CORONA (1960) n Early applications: military reconnaissance CS 128/ES 228 - Lecture 9 a 6

Advantages of satellites n Wide coverage n Vertical (orthogonal) view n Multi-spectral data bands n Rapid data collection CS 128/ES 228 - Lecture 9 a 7

Sources of EM radiation Key distinction: n passive sensing n active sensing Spectral ‘signatures” Top: Lo & Yeung, fig. 8. 1 Bottom: ASTER Spectral Library (http: //speclib. jpl. nasa. gov) CS 128/ES 228 - Lecture 9 a 8

Types of EM radiation used Three important spectral bands: n visible light n infrared radiation n microwave radiation Image from NASA 1987. SAR: Synthetic Aperture Radar. Earth Observing System, Vol. IIf. CS 128/ES 228 - Lecture 9 a 9

Atmospheric attenuation Scattering n caused by aerosols (water vapor, dust, smoke) Absorption § caused by gas molecules (H 2 O, CO 2, O 3) n more intense at shorter wavelengths § each molecule absorbs at a specific wavelength n why the sky is blue § result: atmospheric transmission windows CS 128/ES 228 - Lecture 9 a 10

Transmission windows § UV-visible-IR § Microwave Image from NASA 1987. From Pattern to Process: The Strategy of the Earth Observing System. Vol. II. CS 128/ES 228 - Lecture 9 a 11

Classes of sensors Photographic n panchromatic n color Multi-spectral scanners § sensors for many wavelengths § image scanned across sensors Infrared (IR) § film (near IR) § thermal IR sensors for longer wavelengths Radar § RAdio Detection And Ranging § active imaging CS 128/ES 228 - Lecture 9 a 12

Visual sensors: film types n panchromatic n near-infrared n color Both images from Committee on Earth Observation Satellites http: //ceos. cnes. fr: 8100/cdrom-98/ceos 1/irsd/content. htm CS 128/ES 228 - Lecture 9 a 13

§ IR penetrates haze and light cloud Infrared sensors cover n can be used at night n used by military for camouflage detection n IR ‘signature’ often distinct from visible image CS 128/ES 228 - Lecture 9 a 14

Color IR film § Used with yellow (blueabsorbing) filter n 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 http: //ceos. cnes. fr: 8100/cdrom-98/ceos 1/irsd/content. htm Bottom image: Avery. 1977. Interpretation of Aerial Photographs. 3 rd ed. Burgess Press, Minneapolis, MN. CS 128/ES 228 - Lecture 9 a 15

Multispectral sensors n Visible + IR spectra n Comparison of film and electronic sensor spectral bands Top: Avery 1977. Interpretation of Aerial Photography. Burgess Publ. , Ninneapolis Bottom: ASTER Science page (http: //www. science. aster. ersdac. or. jp/users/parte 1/02 -5. htm#3) CS 128/ES 228 - Lecture 9 a 16

Radar sensors n active sensing n day & night, all weather n less affected by scattering (aerosols) Lo & Yeung, fig. 8. 13 n vertical or oblique perspective CS 128/ES 228 - Lecture 9 a 17

Uses of radar: altimetry n satellite-nadir distance n geoid & topographic measurements n sea elevation, tides & currents n wave/storm measurements Both images from NASA 1987. Altimetric System. Earth Observing System, Vol. IIh. CS 128/ES 228 - Lecture 9 a 18

Uses of radar: SAR n glaciology n hydrology n vegetation science n geology Image from NASA 1987. SAR: Synthetic Aperture Radar. Earth Observing System, Vol. IIf. CS 128/ES 228 - Lecture 9 a 19

Sensor resolution n Spatial: size of smallest objects visible on ground. Ranges from < 1 m to > 1 km. Inversely related to area covered by image n Spectral: wavelengths recorded. Ex. panchromatic film (~0. 2 – 0. 7 µm); Landsat Thematic Mapper bands (0. 06 to 0. 24 µm wide) n Radiometric: # bits/pixel. Ex. Landsat TM (8 bit); AVRIS (12 bit) n Temporal: for satellite, time to repeat coverage. Ex. Landsats 5 & 7 (16 days) CS 128/ES 228 - Lecture 9 a 20

Spatial resolution: analog (film) images Depends on: n lens quality & camera stability n n 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 228 - Lecture 9 a 21

Ground resolution G. R. = scale factor / film resolution Focal length of lens (mm) Altitude of plane (m) 85 300 85 610 Scale of photograph Ground resolution (m) 1: 3, 530 0. 06 3, 000 1: 35, 300 0. 59 3, 000 1: 54, 100 0. 902 CS 128/ES 228 - Lecture 9 a 22

Spatial resolution: digital (satellite) images A sampler of recent (civilian) satellites: Sponsor Satellite (instrument) Year Res. (m) NASA Landsat (Thematic Mapper) 1980 -90 s 30 (MSS) NASA & others EOS Terra (ASTER) 2000 15 - 90 (MSS) France SPOT-3 to 5 19932002 10 to 5 (pan) Space Imaging IKONOS-2 1999 1 (pan) 4 (MSS) Earth. Watch Quickbird-2 2001 0. 6 (pan) 2. 5 (MSS) CS 128/ES 228 - Lecture 9 a 23

Satellite Quickbird 2 image resolution n Commercial venture n 0. 63 m resolution n U. S. trying to discourage open access to finer resolution images Digitalglobe. com CS 128/ES 228 - Lecture 9 a 24

Satellite orbits Geostationary n 36, 000 km above equator Polar n varying heights n often in Sunsynchronous orbits Both diagrams from European Organisation for the Exploitation of Meteorological Satellites www. eumetsat. de/en/mtp/space/polar. html CS 128/ES 228 - Lecture 9 a 25

Geostationary Satellite n no polar coverage n coverage is 24/7 n low ground resolution (~ 1 km) Polar n global coverage n coverage is discontinuous Both diagrams from European Organisation for the Exploitation of Meteorological Satellites www. eumetsat. de/en/mtp/space/polar. html CS 128/ES 228 - Lecture 9 a 26

Geostationary orbits Ex. GOES satellites n Meteorological satellites n GOES-8 at 75 o. W, GOES-9 at 135 o. W n 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 228 - Lecture 9 a 27

Polar orbits Ex. Landsat & Terra satellites n 705 km height, ~100 minute orbit n 185 km swath n 16 day repeat n Sun-synchronous orbits (~0945 a. m. equator crossing) Orbit tracking data from NASA – http: //liftoff. msfc. nasa. gov/realtime/JTrack/eos. html, 5 Mar ‘ 03 CS 128/ES 228 - Lecture 9 a 28