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2024Lillesand_RemoteSensing-Multispectral-L9_Fin3 (1).pptx
2024Lillesand_RemoteSensing-Multispectral-L9_Fin3 (1).pptx
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slide-01
Introduction to Remote Sensing Types of Remote Sensing Systems (optical) Multispectral remote sensing The collection of reflected, emitted energy from an object or area of interest in multiple bands of the electromagnetic spectrum (Jensen, 2000). Thermal remote sensing Data collection only in the thermal portion of the electromagnetic spectrum (in one or more bands). Hyperspectral remote sensing Data collection in hundreds of very narrow spectral bands. 1
slide-02
Digital image format Stored in a raster (matrix, array) format Each digital value is located at a specific row (i) and column (j) in a matrix. Dataset consists of n individual multispectral bands. Brightness values (BR): pixel (picture element) values 8-bit: 0-255; 10-bit: 0-1023; and 12-bit: 0-4095 quantization level of the sensor systems 2
slide-03
Multispectral remote sensing systems Multispectral remote sensing systems sense the electromagnetic range from 0.4 to 14 µm using discrete detectors and scanning mirrors (across track) Landsat MSS, Landsat TM, Landsat ETM+ linear arrays (along track) SPOT HRV, SPOT HRVI, IRS LISS, IKONOS, Quickbird 3
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Multispectral imaging using discrete detectors and scanning mirrors Differences between this system and a camera system • discrete electronic detectors • a rotating mirror is added in front of the lens of camera • films are changed to photo-sensitive detectors and magnetic tapes 4
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Across track Across-track scanners scan the Earth in a series of lines. The lines are oriented perpendicular to the direction of motion of the sensor platform (i.e. across the swath). 5
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Across track IFOV (C) (instantaneous field of view): the angle within which incident energy is focused on the detector. Field of view (E): the sweep of the mirror, used to record a scan line. Swath width (F): determined by the field of view and altitude of the platform A: rotating mirror B: detector D: spatial resolution 6
slide-07
Introduction to Remote Sensing Multispectral Scanning System (MSS) Across –track of the scanning Along –track of the satellite swath width Each scan will collect six image lines. Each scene covers: 185 km X 170 km a spatial resolution: 79 m X 57 m Six detectors per band (24 detectors total). 7
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Along track Along-track: detectors record data along a swath which is perpendicular to the flight line. 8
slide-09
Along track uses a linear array detectors (A) detectors are push along in the flight track direction (along track) referred to as pushbroom scanner each individual detector measures the energy for a single ground resolution cell (D). B: focal plane C: lens 9
slide-10
Introduction to Remote Sensing Multispectral imaging using linear arrays (pushbroom, SPOT HRV) Use thousands of detectors arranged linearly called "charge-coupled devices" (CCDs) instead of a few detectors used by MSS and TM panchromatic (PAN) mode multispectral (XS) mode This sensor images a complete line of the ground scene in the cross-track direction in one look. A mirror with the view angle of 4.13° is used to allow ±27° off nadir (oblique) 10 observation, allows acquisitions of stereo-pair images more frequently (3-5 days)
slide-11
Introduction to Remote Sensing Comparison of a linear sensor and a scanning sensor A linear sensor is superior than a scanning sensor A more accurate measurement from CCDs no moving mirror, no mechanical scanning, hence are more reliable and have a longer life dwell longer on a specific portion of the terrain, --stronger signals can be recorded CCDs are smaller in size and weight, and require less power than across track scanners A disadvantage ? Disadvantage: of a linear sensor is the difficulties involved in calibrating thousands of detectors. 11
slide-12
Satellite orbits Orbit is the path followed by a satellite. Orbit elements altitude period cycle inclination 12
slide-13
Altitude Height of the platform above the earth’s surface. Landsat 7 is in orbit at 705 km (420 mi) above the earth. Source: http://www.sci-ctr.edu.sg/ssc/publication/remotesense/landsat.htm 13
slide-14
Period The time of a satellite to complete one orbit. Landsat 7 orbits of the earth once every 99 min, resulting in 14.5 orbits per day. 75Þ 4 60Þ 3 45Þ 30Þ 15Þ 2 1 14 13 12 11 10 9 8 7 6 Latitude 0Þ 15Þ 15 orbit number 30Þ 5 45Þ 60Þ 75Þ 14 Jensen, 2000
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Orbit cycle The length of time needed for the satellite to retrace its path.?? e.g. 16 days i.e. passing over the same point June 1, June 17, July 3, 1999 1999 1999 on the Earth's surface directly below the satellite (called the nadir point) for a second time. Varies with each satellite The temporal resolution is every 16 days. 15
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Inclination Refers to the angle at which a satellite crosses the equator. near-polar orbits with an inclination close to 900 Example? Landsat 7 geostationary orbits with an inclination of 00, example? GOES Weather satellites 16
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Near-polar orbits Most of the RS satellite platforms basically N-S orbit (constant E-W position) + the Earth's W-E rotation allow complete coverage of the Earth's surface after one complete cycle of orbits https://www.youtube.com/watch?v=P- lbujsVa2M Source: NASA 17
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Near-polar orbits Sun-synchronous The orbital plane processes around the Earth at the same angular rate at which Earth moves around the Sun This characteristic causes the satellites to cross the equator at the same local time (9:30-10:00 am) on the illuminated side of Earth. 18
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Geostationary orbits Satellites at very high altitudes (ca. 36,000 km) Revolve at speeds that match the rotation of the Earth ( seem stationary) Examples? E.g. weather & communications satellites Collect info over the same portion of the earth's surface at all times https://www.youtube.com/watch? v=FsfcIEmR_b0 19
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Landsat series satellites Initiated by NASA (The National Aeronautics and Space Administration ), encouraged by the U.S. Department of Interior in 1967 The first of the Landsat series was launched in 1972. called Earth Resources Technology Satellites (ERTS-1) renamed as Landsat 1 later Landsat 2 was launched in 1975 (ERTS-B) Landsat 3 had a short life, and launched in 1978. Landsat 4: launched in 1982 Landsat 5: launched in 1984 Landsat 6: launched unsuccessfully in 1993 Landsat 7: launched in April 15, 1999 NASA and USGS currently share the responsibility of Landsat 7 operations, data processing, archive20 and distribution.
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Landsat series satellites Landsat 8: The latest was launched February 11, 2013 Landsat 8 is offset 12 hours from Landsat 7 Landsat 9, Launch: Sept. 27, 2021 https://landsat.gsfc.nasa.gov/satellites/landsat-9/ 21
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Landsat series satellites Source: https://landsat.gsfc.nasa.gov/satellites/landsat-9/ 22
slide-23
Landsat circular orbits (1-3) Orbits around Earth at an altitude of 919 km (Landsat 1 to 3) Had an orbital inclination of 990, nearly polar orbits Earth once every 103 min, 14 orbits per day Sun-synchronous orbit Revisit rate: 18 days (Landsat 1 to 3) 23
slide-24
MSS parameters MSSs have been used on Landsat - 1, 2, 3, 4, 5. Landsat 1, 2 Landsat 4, 5 B4 0.5 - 0.6 µm B1 B5 0.6 - 0.7µm B2 B6 0.7 - 0.8 µm B3 B7 0.8 - 9.1 µm B4 Each scene: covers 185 km X 170 km a spatial resolution of 79 m X 57 m instantaneous field of view (IFOV) of 79 m X 79 m 24
slide-25
Major changes of Landsat Thematic Mapper (TM) as compared to the MSS (Landsat 4 and 5) Increased the number of spectral bands Improved spatial and spectral resolution Orbit changed from a 919-km to a 705-km, influence? Increased the angle of view from 11.56° to 14.92° Repetitive rate changed from 18 to 16 days 16 detectors are used to collect the data for B1-B5, B7 4 detectors are used to collect the thermal data Blue TM1 0.45 - 0.52 µm 30 m Green TM2 0.52 - 0.60 30 m Red TM3 0.63 - 0.69 30 m Near IR TM4 0.76 - 0.90 30 m SWIR TM5 1.55 - 1.75 30 m SWIR TM7 2.08 - 2.35 30 m Thermal IR TM6 10.4 - 12.5 µm 120m 25
slide-26
Landsat • Swath is 183 km wide • 233 orbits, for each 16 day cycle 26
slide-27
Introduction to Remote Sensing Major changes of Landsat Enhanced Thematic Mapper Plus (ETM+) as compared to the TM The addition of the new panchromatic band Improved spatial resolution with the Thermal infrared band 6 TM1 0.45 - 0.52 µm 30 m TM2 0.52 - 0.60 30 m TM3 0.63 - 0.69 30 m TM4 0.76 - 0.90 30 m TM5 1.55 - 1.75 30 m TM7 2.08 - 2.35 30 m TM6 10.4 - 12.5 60 m PAN 0.52 - 0.90 15 m 27
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Landsat 7 circular orbits Orbits around Earth at an altitude of 705 km 8 degrees off a polar orbit, nearly polar One orbit takes about 99 minutes (14.5 per day) Sun-synchronous orbit by following earth’s rotation with each pass, it can keep crossing the equator at the same time always crosses equator at around 10 AM. The repeat cycle is 16 days Distance between ground tracks of consecutive orbits is 2,752 km at equator because of the earth’s rotation 28
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Landsat 7 ETM+ Spectral and spatial resolution of bands Band wavelength spectrums are slightly different from LANDSAT 5 29
slide-30
Landsat band properties 1 =Blue, 0.45-0.52 µm mapping coastal water areas, differentiating between soil and vegetation, forest type mapping, and detecting cultural features. 2 =Green, 0.52-0.60 µm Vegetation identification and assessment of vigor, cultural feature identification. 3 =Red, 0.63-0.69 µm discriminating between many plant species; determining soil boundary and geological boundary delineations as well as cultural features. 4 =Reflective-infrared, 0.76-0.90 µm This band is especially responsive to the amount of vegetation biomass present in a scene; crop identification and emphasizes soil/crop and land/water contrasts. 5 =Mid-infrared, 1.55-1.75 µm This band is sensitive to the amount of water in plants; crop drought studies and in plant health analyses; discriminate between clouds, snow, and ice. 6 =Thermal-infrared, 10.40-12.50 µm This band is useful for vegetation and crop stress detection, heat intensity, insecticide applications, and for locating thermal pollution. locating geothermal activity. 7 =Mid-infrared, 2.08-2.35 µm for the discrimination of geologic rock type and soil boundaries, as well as soil and vegetation moisture content. 30
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Landsat band properties Band Nominal Spectral applications location 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- Veg moisture, soil moisture, diff of soil from clouds 1.75 mm) 6 Thermal infra red Veg stress analysis, soil moisture, thermal mapping 7 mid infra red(2.08- Discriminating mineral and rock types, veg 2.35 mm) moisture 31
slide-32
Landsat 9 with OLI, and Thermal Infrared (TIRS-2) Spectral and spatial resolution of bands Sept. 27, 2021 Launch, see link: https://geonarrative.usgs.gov/landsat-9-road-to-launch/ Landsat Science Band wavelength spectrums are slightly different from LANDSAT 5 32
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Landsat scene Scenes are then indexed by the path and a row 33
slide-34
Landsat 4 and 5 Worldwide Reference System Jensen, 2000 34
slide-35
Brazilian Amazon Case Study Area Rio Branco, Acre State, Brazil Fig. 2.-Landsat Thematic Mapper Fig. 1.-Legal Amazon of Brazil World Referencing System II (WRS II), Path 2, Row 67 Source: Basic Science and RemoteSensing Initiative, Michigan State U. (http://bsrsi.msu.edu/trfic/browser/legalamazon_frame.html) Brazil 35
slide-36
Rio Branco and BR 364 Highway, Acre State, Brazil NW Section processed Fig. 4. - Landsat TM Color Infrared image, Path 2, Row 67, 8/30/1992 Forest Spectral Sig. Deforested Spectral Sig. 2nd Growth Spectral Sig. BR 364 Highway Rio Branco 36
slide-37
Landsat products http://earthexplorer.usgs.gov They have a browser for finding and ordering Landsat imagery these and a variety of other RS images 39
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Landsat products Downloading Imagery, https://www.youtube.com/watch?v=Wn_G4fvitV8 40