satellite image interpretation
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SATELLITE IMAGE INTERPRETATION
Course: Introduction to RS & DIP
Mirza Muhammad WaqarContact:
mirza.waqar@ist.edu.pk+92-21-34650765-79 EXT:2257
RG610
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Contents
Geographical Information System Remote Sensing & Satellite Image Processing Color Space Landsat 7 spectral bands Spectral Reflectance Curves Image Interpretation Spectral Ratioing Indices
Software
Geographical Information System (GIS)
Data
Site Suitability AnalysisSpatial Analysis3D AnalysisHydrological AnalysisFinding Shortest PathFinding Closest FacilityChange Detection
Methods
Remote Sensing & Satellite Image Processing
Spectral vs Spatial
Spectral pattern recognitionFamily of classification procedures that utilize pixel by pixel spectral information as the basis for automated land cover classification.
Spatial pattern recognitionCategorization of image pixels on the basis of their spatial relationship with pixels surrounding them.
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Landscape visualization
The ground view Field investigation and survey Great details, sample taken and field measurements High cost, time consuming, physically demanding
The bird-eye view Natural observation, perspective view Difficult for mapping and locationing
The orthographic view Professional aerial survey and space mapping High locational accuracy, fast coverage, economic Lack of 3-dimensional information, skill demanding
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The ground view
Ground view of Mt. Everest, the highest spot on earth.
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Visualization – Bird-Eye View
Bird-eye view of Mt. Everest. The photo was taken by astronauts on the International Space Station.
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Visualization – Orthographic View
Orthographic view of Mt. Everest. The photo was taken by
astronauts on the International Space Station in 1993.
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The concepts of image interpretation
Image interpretation: the process of identifying objects or conditions in images and determining their meaning or significance.
The interpreter’s task: use scientific tools and methodology to arrive at objective findings.
Geographical knowledge is needed to relate the visible characteristics on the image to the real-world geographical features, even though some of these features may not be physically visible.
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Spatial interpretation
Spatial interpretation means identifying geographical features using spatial characteristics of objects shown on images.
The most important tasks for spatial interpretation is to establish interpretation keys, i.e. identifying the typical spatial and spectral patterns of known geographical features.
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Multi-runway airfield used by carrier-based pilots for practicing short takeoffs and
landings (Broward County, Florida)
Low-altitude photograph of the Pentagon Building, headquarters of the US
Department of Defense
Obvious features
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Keys for image interpretation
Shape Size Pattern Shadow
Tone or colour Texture Association Site
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Shape
Some man-made features have unique shapes.
Alluvial fans along the east side of Death Valley, California. Alluvial fans can be easily recognised by their fan shape and adjacency to mountain fronts.
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Pyramids
Ground view of the Great Pyramids, Egypt.
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Shape
Centre-pivot irrigation system in Morrow County, Oregon. Most of the fields are planted with wheat.
Alluvial fans at the north of Turpan Depression, Xinjiang, China.
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A Centre-Pivot Irrigation System
A centre-pivot irrigation system in Ili, Xinjiang, China.
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An Alluvial fan
Ground view of alluvial fans at the north of Turpan Depression, Xinjiang, China.
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Size
Panchromatic photo of Bangkok, 1982. Note the size of buildings tends to indicate the nature and usage of them.
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The contrast between sand dunes (left) and loess (right) landscapes found near Yulin, Shannxi, northern China. The mobile sand dunes are well recognised by their repeated patterns, while the high density of gullies of the loess landscape suggests severe soil erosion and mass movement.
Pattern
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Natural Patterns
The patterns of forest and wetland show significant variation on remotely sensed images.
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Loess Landscape
The high density of gullies is the key for image interpretation of the loess landscape.
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Shadow
Shadow shown with low sun angle is the key to the interpretation of shape of Mt. Everest.
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Tone and colour are used to identify agricultural fields. The fields with crops or harvested are clearly separated by their tones and colours. Also note the tone difference shown on the bare fields indicating different soil moisture contents.
Tone or Color
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Texture
Textures associated with forest, pasture and cropland. The colour photograph shows the strong contrast in texture between forest (dark and coarse), pasture (light and smooth and farmland (light and smooth with regular road and drainage network).
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A chain of oasis is located along the toe of an alluvial fan in Turpan Depression, Xinjiang, China. There is a good supply of shallow groundwater to support irrigation system and human settlement in the extremely dry area.
Association
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Sea Port at Kowloon Peninsula of Hong Kong. The site is characterised by regular shore line and large concrete area of loading zones. The extensive transportation network also a good key to identify the port.
Site
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Spectral interpretation
The spatial interpretation keys are also employed to interpret multi-spectral images. Scale Spatial distortion
Multi-spectral images, however, add one more dimension (i.e. the spectral space) for image interpretation.
Understanding spectral signature is therefore mandatory for image interpretation.
Color Space
Red + Blue Magenta
Green + BlueCyan
Red + Green Yellow
Primary Colors
Magenta + Cyan Blue
Yellow + Cyan Green
Yellow + Magenta Red
Secondary Colors
Landsat 7
Enhanced Thematic Mapper Plus (ETM+)
Landsat 7Wavelength
(micrometers)Resolution (m)
Band 1 0.45 - 0.52 30
Band 2 0.52 - 0.60 30
Band 3 0.63 – 0.69 30
Band 4 0.77 – 0.90 30
Band 5 1.55 – 1.75 30
Band 6 10.40 – 12.50 60
Band 7 2.09 – 2.35 30
Band 8 0.52 – 0.90 15
Spectral Reflectance Curves of Different Land Covers
Source: Yasir YaqoobWateen Telecom
Reflection of Different Land Covers in Landsat Bands
* Vegetation Soil Snow Cloud Water
Band 1 10 % 20 % 97 % 70 % 5 %
Band 2 17 % 24 % 96 % 70 % 8 %
Band 3 10 % 28 % 94 % 70 % 2 %
Band 4 48 % 35 % 85 % 66 % 1 %
Band 5 38 % 50 % 10 % 52 % 1 %
Band 7 20 % 55 % 8 % 53 % 1 %
Islamabad Capital Territory – Raw Image
Vegetation: Green Dominating YellowSoil: ?Snow: ?Cloud: ?Water: ?
Band Combination RGB:542Vegetation:R=38% G=48% B=17%Grey Tone=17%-----------------------R=21% G=31% B=0%Yellow Tone= 21%-----------------------R=0% G=10% B=0%
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