View
219
Download
0
Embed Size (px)
Citation preview
CS 128/ES 228 - Lecture 9a 1
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 9a 3
History of remote sensing
Earliest vehicle was …?
Tournachon (‘Nadar’) took 1st aerial photograph in 1858 (since lost)
Earliest conserved aerial photograph: Boston, J. Black, 1860
Early applications were in military reconnaissance
CS 128/ES 228 - Lecture 9a 4
WWII – heavy use of aerial reconnaissance
Images: Avery. 1977. Interpretation of Aerial Photographs. 3rd ed. Burgess Press, Minneapolis, MN.
CS 128/ES 228 - Lecture 9a 6
Satellite sensing
Russian Sputnik (1957)- radio transmitter only
Rapid response by US:CORONA (1960)
Early applications: military reconnaissance
CS 128/ES 228 - Lecture 9a 7
Advantages of satellites
Wide coverage
Vertical (orthogonal) view
Multi-spectral data bands
Rapid data collection
CS 128/ES 228 - Lecture 9a 8
Sources of EM radiation
Key distinction: passive sensing active sensing
Spectral ‘signatures”
Top: Lo & Yeung, fig. 8.1 Bottom: ASTER Spectral Library (http://speclib.jpl.nasa.gov)
CS 128/ES 228 - Lecture 9a 9
Types of EM radiation used
Three important spectral bands: visible light infrared radiation microwave radiation Image from NASA 1987. SAR: Synthetic Aperture Radar.
Earth Observing System, Vol. IIf.
CS 128/ES 228 - Lecture 9a 10
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 (H2O, CO2, O2, O3)
each molecule absorbs at a specific wave-length
result: atmospheric transmission windows
CS 128/ES 228 - Lecture 9a 11
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 9a 12
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 228 - Lecture 9a 13
Visual sensors: film types
panchromatic
near-infrared
color
Both images from Committee on Earth Observation Satellites http://ceos.cnes.fr:8100/cdrom-98/ceos1/irsd/content.htm
CS 128/ES 228 - Lecture 9a 14
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 228 - Lecture 9a 15
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 http://ceos.cnes.fr:8100/cdrom-98/ceos1/irsd/content.htmBottom image: Avery. 1977. Interpretation of Aerial Photographs. 3rd ed. Burgess Press, Minneapolis, MN.
CS 128/ES 228 - Lecture 9a 16
Multispectral sensors Visible + IR spectra
Comparison of film and electronic sensor spectral bands
Top: Avery 1977. Interpretation of Aerial Photography. Burgess Publ., NinneapolisBottom: ASTER Science page (http://www.science.aster.ersdac.or.jp/users/parte1/02-5.htm#3)
CS 128/ES 228 - Lecture 9a 17
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 228 - Lecture 9a 18
Uses of radar: altimetry
satellite-nadir distance
geoid & topographic measurements
sea elevation, tides & currents
wave/storm measurements
Both images from NASA 1987. Altimetric System. Earth Observing System, Vol. IIh.
CS 128/ES 228 - Lecture 9a 19
Uses of radar: SAR
glaciology
hydrology
vegetation science
geology
Image from NASA 1987. SAR: Synthetic Aperture Radar. Earth Observing System, Vol. IIf.
CS 128/ES 228 - Lecture 9a 20
Sensor resolution
Spatial: size of smallest objects visible on ground. Ranges from < 1m to > 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 228 - Lecture 9a 21
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 228 - Lecture 9a 22
Ground resolution
G. R. = scale factor / film resolution
Focal length of lens (mm)
Altitude of plane (m)
Scale of photograph
Ground resolution (m)
85 300 1:3,530 0.06
85 3,000 1:35,300 0.59
610 3,000 1:54,100 0.902
CS 128/ES 228 - Lecture 9a 23
Spatial resolution: digital (satellite) images
A sampler of recent (civilian) satellites:Sponsor Satellite (instrument) Year Res. (m)
NASA Landsat (Thematic Mapper) 1980-90s 30 (MSS)
NASA & others
EOS Terra (ASTER) 2000 15 - 90 (MSS)
France SPOT-3 to 5 1993-2002
10 to 5 (pan)
Space Imaging
IKONOS-2 1999 1 (pan)4 (MSS)
EarthWatch Quickbird-2 2001 0.6 (pan)2.5 (MSS)
CS 128/ES 228 - Lecture 9a 24
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 228 - Lecture 9a 25
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 Satelliteswww.eumetsat.de/en/mtp/space/polar.html
CS 128/ES 228 - Lecture 9a 26
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 Satelliteswww.eumetsat.de/en/mtp/space/polar.html
CS 128/ES 228 - Lecture 9a 27
Geostationary orbits
Ex. GOES satellites Meteorological
satellites
GOES-8 at 75oW, GOES-9 at 135oW
5 bands (1 visible, 4 thermal infrared) Image from NASA – Goddard Space Flight
Center, NOAA GOES satellite, Hurricane Floyd, 15 Sep ‘99