©2008 austin troy lecture 21: major types of satellite imagery by austin troy and weiqi zhou...

©2008 Austin Troy

Lecture 21:Major Types of Satellite Imagery

By Austin Troy and Weiqi ZhouUniversity of Vermont

------Using GIS--Introduction to GIS

©2008 Austin TroyMaterials by Austin

Troy and Weiqi Zhou except where noted ©

2007

Major Satellite Systems

• High spatial resolution

– Quickbird, IKONOS, OrbView-3, SPOT-5 PAN, IRS-P6

• Medium spatial resolution

– Landsat-5 TM, Landsat-7 ETM+, ASTER, SPOT

• Low spatial resolution

– MODIS, ENVISAT, GOES, AVHRR, MSS



2007

Orbits•Most of these satellites are in sun-synchronous orbit

•The satellite passes over the same part of the Earth at roughly the same local time each day

•Its “inclination” is about 8 degrees off of polar orbit

•The fact that the earth is not perfect sphere makes the orbital plane rotate slowly around the earth (this would not happen if it were perfectly polar)



2007

Orbits

Source:http://ltpwww.gsfc.nasa.gov/IAS/handbook/handbook_htmls/chapter6/chapter6.html



2007

Orbits•The slow motion of that orbital plane matches the latitudinal motion of the sun in the sky over the year

•Maintains similar sun angles along its ground trace for all orbits

•That means that the area the sun flies over always get the same sunlight angle, which gives constant lighting

Source:http://hdsn.eoc.nasda.go.jp/experience/rm_kiso/satellit_type_orbit_e.html



2007

Scanners•Pushbroom (along track) vs. Whiskbroom (across track)

•SPOT and IKONOS: Pushbroom

•Landsat: Whiskbroom

•Pushbroom scanners generally have higher radiometric resolution because they have longer “dwell time” than across-track scanners, which move laterally across landscape as also move forward

Source: http://www.sci-ctr.edu.sg/ssc/publication/remotesense/spot.htm



2007

LANDSAT• First started by NASA in 1972 but later turned over to NOAA

• Since 1984 satellite operation and data handling are managed by a commercial company EOSAT•LANDSAT-7 launched in 1999; developed scan line error in 2003• Only 5 is still working; outdated Source: http://www.sci-ctr.edu.sg/ssc/publication/remotesense/landsat.htm



2007

LANDSAT•LANDSAT 4 and 5 had two types of sensors, MSS (multi-spectral scanner) and TM (thematic mapper):

•MSS:Started on LANDSAT 1, terminated in late 1992. 80 m resolution with four spectral bands from the visible green to the near-infrared (IR) wavelengths. Only Landsat 3’s MSS sensor had a fifth band in the thermal-IR.

Introduction to GIS



2007

LANDSAT Thematic Mapper

*

*

* Mid infra red

• Spatial and spectral resolution

• Radiometric resolution: 8 bits (256 DNs)

• Temporal resolution: 16 days.



2007

LANDSAT TM•An example:August 14, 1999 (left) and October 17, 1999 (right) images of the Salt Lake City area

• Differences in color due to growing season



2007

LANDSAT 7•Uses a new sensor called Enhanced Thematic Mapper Plus (ETM+)

•Stressed continuity with LANDSAT 4 and 5 in that uses similar orbit and repeat patterns, as well as a similar 185 km swath width for imaging

•Check out the movie Source: http://ltpwww.gsfc.nasa.gov/IAS/handbook/handbook_htmls/chapter2/chapter2.html



2007

• Characteristics of ETM+: Band wavelength spectrums are slightly different from LANDSAT 5 TM

LANDSAT-7 ETM+ BAND CHARACTERISTICS

Band Number

Nominal spectrum

Spectral Range (µ)

Ground Resolution

(m)

Data Lines Per Scan

Data Line Length (bytes)

1 Blue .450 to .515 30 16 6,600

2 green .525 to .605 30 16 6,600

3 red .630 to .690 30 16 6,600

4 Near IR .775 to .900 30 16 6,600

5 mid IR 1.550 to 1.750 30 16 6,600

6 Thermal IR 10.40 to 12.50 60 8 3,300

7 mid IR 2.090 to 2.35 30 16 6,600

8 panchromatic .520 to .900 15 32 13,200

Enhanced Thematic Mapper Plus



2007

LANDSAT TM: applications

Introduction to GIS

Band Nominal Spectral location

applications

1 Blue Water body penetration, soil-water discrimination, forest type mapping, cultural feature ID

2 Green Green reflectance peak of veg, for veg ID and assessment of vigor, cultural feature ID

3 Red Chlorophyll absorption region, plant species differentiation, cultural feature ID

4 Near infra red Veg types, vigor and biomass content, dilineating water bodies, soil moisture assessment

5 mid infra red (1.55-1.75 m)

Veg moisture, soil moisture, diff of soil from clouds

6 Thermal infra red Veg stress analysis, soil moisture, thermal mapping

7 mid infra red(2.08-2.35 m)

Discriminating mineral and rock types, veg moisture



2007

LANDSAT•Its repeat cycle is about 16 days and always crosses equator at around 10 AM.

•Orbit takes about 99 minutes (14.5 per day)

•Distance between ground tracks of consecutive orbits is 2752 km at equator because of the earth’s rotation

•By following earth’s rotation with each pass, it can keep crossing the equator at the same time

Introduction to GIS



2007

LANDSAT•Swath is 183 km wide, although that includes overlap, since data frame is 170 km

•233 orbits, for each 16-day cycle

Source: http://eosims.cr.usgs.gov:5725/DATASET_DOCS/landsat7_dataset.html



2007

LANDSAT•Scenes are then indexed by the path and a row

Source: http://eosims.cr.usgs.gov:5725/DATASET_DOCS/landsat7_dataset.html



2007

LANDSAT 7• LANDSAT 7 has an excellent mission coverage archive

Source: http://ltpwww.gsfc.nasa.gov/IAS/handbook/handbook_htmls/chapter6/chapter6.html



2007

LANDSAT Products•All data older than 2 years return to "public domain" and are distributed by the Earth Resource Observation System (EROS) Data Center of the US Geological Survey

•Available at http://edcwww.cr.usgs.gov/products/satellite/landsat7.html

•The LANDSAT Reference system catalogues the world into 57,784 scenes, each 115 miles (183 kilometers) wide by 106 miles (170 kilometers) long.



2007

LANDSAT Imagery• Composite of Red, Green and Blue. Shows manmade features as well as densely forested areas and agricultural lands.



2007

LANDSAT Imagery• Composite of NIR, Red and Green. Shows manmade features as well as densely forested areas and agricultural lands.



2007

LANDSAT Imagery• Composite of shortwave infrared, Near-Infrared and Red. Shows manmade features as well as densely forested areas and agricultural lands



2007

LANDSAT Imagery

Introduction to GIS



2007

LANDSAT Imagery

Introduction to GIS

Composite of shortwave infrared, Near-Infrared and Red. Shows manmade features as well as densely forested areas and agricultural lands



2007

LANDSAT Imagery

Introduction to GIS

Same bands: shows wetlands, urban, open water, forest



2007

LANDSAT Imagery

Introduction to GIS

Same bands: light yellow-green color represents northern hardwood forest. The dark green patches represent various conifer species



2007

SPOT•Launched by France

• Stands for Satellite Pour l'Observation de la Terre

•Operated by the French Space Agency, Centre National d'Etudes Spatiales (CNES).



2007

SPOT• SPOT 1 launched 1986, decommissioned and the reactivated in 1997

• SPOT 2 launched 1990, still going

• SPOT 3 launched 1993 and stopped functioning 1996

• SPOT 4 launched in 1998, still going

• SPOT 5 launched in 2002



2007

SPOT• Each SPOT satellite carries two HRV (high-resolution visible) sensors, constructed with multilinear array detectors, or “pushbroom scanners”

• These record multispectral image data along a wide swath




2007

SPOT• The position of each HRV unit can be changed by ground control to observe a region of interest that is at an oblique angle to the satellite—up to ±27º relative to the vertical.

• Off-nadir viewing allows for acquisition of stereoscopic imagery (because of the parallax created) and provides a shorter revisit interval of 1 to 3 days.




2007

SPOT• Oblique viewing capacity

– Greatly improve the viewing frequency (temporal resolution): allows it to image any area within a 900 kilometer swath; can be used to increase the viewing frequency for a given point during a given cycle. For a given location, the interval ranges from a maximum of 4 days to a minimum of 1 day.

– Any point on 95% of the earth may be imaged any day by one of the three satellites.

Source:http://www.spot.com/home/system/introsat/acquisi/welcome.htm



2007

SPOT

Source: http://www.spotimage.fr/html/_167_224_555_233_.php

• Two modes: panchromatic and multispectral



2007

SPOT•Some examples: mosaic false color tiles of Australia



2007

SPOT



2007

IKONOS• Developed by Space Imaging, launched 1999

• Has sun-synchronous orbit and crosses equator at 10:30 AM

• Highly maneuverable: can point at a new target and stabilize itself in seconds, enabling it to follow meandering features

• The entire spacecraft moves, not just the sensors



2007

IKONOS• Can collect data at angles of up to 45°from the along track and across track axes: allows for side by side and fore and aft stereoscopic imaging

• At its nadir it has 11 km swath width

• 11 km by 11 km image size, but user specified strips and mosaics can be ordered

• Employs a linear array scanner



2007

IKONOS• Resolutions

– Panchromatic band (.45 to .90 m) at 1 m spatial resolution.

– Four multispectral bands at 4 m spatial resolution.

• Blue (.45 to .52 m) green (.51 to .60 m) , red (.63 to .70 m), near IR (.76 to .85 m)

– Radiometric resolution: 11 bits, or 2048 values.

– Temporal: Ground track repeats every 11 days.

–For a gallery of images, see: http://www.satimagingcorp.com/gallery-ikonos.html



2007

IKONOS data• Here is 1m IKONOS view of suburbs, near winter Olympics

Source: spaceimaging.com



2007

IKONOS data•1m IKONOS view of Dubai




2007

IKONOS data•1m IKONOS pan image of Rome




2007

IKONOS data•1m image of “Survivor” camp in Africa


©2008 Austin Troy

Some other satellite platforms

• Quickbird

• IRS system: from India

• ERS: European remote sensing satellite

• Aster: a USGS sensor flying on Terra Satellite

• AVHRR: radar

©2008 austin troy lecture 21: major types of satellite imagery by austin troy and weiqi zhou...

Documents

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austin troy lecture

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pushbroom landsat

mss slide

landsat tm

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