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Chapter 3

Chapter 3. Introduction to airphoto interpretation Introduction to Remote Sensing Instructor: Dr. Cheng-Chien Liu Department of Earth Science National Cheng-Kung University Last updated: 16 April 2003. 3.1 Introduction. Airphoto interpretation:

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Chapter 3

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  1. Chapter 3 Introduction to airphoto interpretation Introduction to Remote Sensing Instructor: Dr. Cheng-Chien Liu Department of Earth Science National Cheng-Kung University Last updated: 16 April 2003

  2. 3.1 Introduction • Airphoto interpretation: • raw data  human brain processing  information  communicate • History • Balloon photographs (1858) • WWI  military reconnaissance tool • WWII  CD film • After WWII  wide spread

  3. 3.2 fundamentals of airphoto interpretation • Photo interpreter • Training • Experience • Keen power of observation coupled with imagination & patience • Thorough understanding of the phenomenon • Knowledge of the geographic region • Supporting materials • Maps • Field observations

  4. 3.2.1 elements of airphoto interpretation • Airphoto interpretation departs from daily image • The portrayal of features from an overhead, often unfamiliar perspective • l outside visible range • Unfamiliar scales and resolutions • Basic characteristics: • Shape • Size • Pattern

  5. 3.2.1 elements of airphoto interpretation (Cont.) • Basic characteristics (cont.) • Tone • Texture • Shadows  topographic variations  geologic landform • Site: aid in the identification of vegetation types • Association : e.g. a ferris wheel  amusement park

  6. 3.2.2 Photo interpretation strategies • Direct recognition • e.g. identification of highway interchange • Inference of site conditions: • e.g. infer the buried gas pipeline  light-toned linear streals • e.g. infer the type of crop  crop calendar • Detective  put all evidence  solve a mystery • The interpreter uses the process of convergence of evidence to successively increase the accuracy and detail of the interpretation

  7. 3.2.3 Airphoto interpretation keys • Help the interpretation in an organized and consistent manner. • Two basic parts • A collection of annotated or captioned stereograms • A graphic or word descrioption • Two general types • Selective key • Elimination key  more positive answer but may result in erroneous answers. • Dichotomous key (Fig 3.1)

  8. 3.2.3 Airphoto interpretation keys (cont.) • More easily constructed and more reliably utilized for cultural feature identification than for vegetation or landform identification • Crop , tree identification  region-by-region, season-by-season.

  9. 3.2.4 Film-filter combinations • Affect the amount of information that can be interpreted from the image

  10. 3.2.5 Temporal aspects of photo interpretation • Vegetative growth, soil moisture  vary during the year • Observe several time  better result

  11. 3.2.6 Photo scale • Table 3.1: typical scales and areas of coverage • Small~1:50,000~medium~1:12,000~large • Small  reconnaissance mapping, large area resource assessment, general resource management planning • Medium  identification, classification, mapping of tree species, agricultural crop type, vegetation community and soil type • Large  intensive monitoring of the damage caused by plant disease, insects or tree blowdown, emergency response to hazardous waste sills and for the intensive site analysis of hazardous waste sites.

  12. 3.2.6 Photo scale (cont.) • NHAP I: • 1980~1985, 1:58,000, 1:80,000, 13200m, leaf-off • NHAP II: • 1985~1987 , leaf-on. • NAPP: • 1:40,000, leaf-on, -off

  13. 3.2.7 Approaching the interpretation process • Photographic materials, interpretation equipment, goals of the interpretation  no single right way to do. • Examples of requirement • Identify and count • Identify anomalous conditions • Delineate discrete areal units • Classification system or criteria  separate categories • Minimum mapping unit (MMU) (Fig 3.2) • From higher contrast one to lower one • From the general to the specific • delineate photographic regions. (tone, texture….)

  14. 3.2.8 photo preparation and viewing • Important factors: • Relevant collateral sources of information (maps, field reports, ….) • Good lighting & access to equipment • Systematically labeled and indexed • Boundary delineations • Fiducial marles, road intersections  registration

  15. 3.2.8 photo preparation and viewing (cont.) • Effective areas: • Definition: central, bounded by lines bisecting the area of overlap with every adjacent photograph • Advantages • Cover entire photo without duplicate effort. • The least relief displacement • Construction  transfer points • Disadvantages of lelineating effective areas on each photos  need twice efforts • Sometimes, only for every other photo

  16. 3.3 Basic photo interpretation equipment • 3 purposes • Viewing • Making measurements • Transfer interpreted information to base maps or digital databases

  17. 3.3 Basic photo interpretation equipment (cont.) • Binocular vision  stereoscopic view  3-D view • Stereopairs, stereograms • Simple lens stereoscope (Fig 3.3) • Test stereoscopic vision (Fig 3.4) (Table 3.2)  elevation • One-weak eyesight • Cannot get stereoscopic view • But still can be a good interpreter  monocular view • Viewing the stereogram without a stereoscope

  18. 3.3 Basic photo interpretation equipment (cont.) • Lens stereoscopes • Fig 3.3 • Pros: portable, cheap Cons: cannot view the entire photo • Lens spacing: 45~75mm • Lens magnification: typically 2 power

  19. 3.3 Basic photo interpretation equipment (cont.) • Mirror stereoscopes • Fig 3.5 • Pros: broader view, a pair of 240 mm photos, measurable. Cons: large and costly • Magnification: 2~4 power

  20. 3.3 Basic photo interpretation equipment (cont.) • Scanning mirror stereoscope • Fig 3.6 • Built-in provision • Magnification: 1.5~4.5 power • Zoom stereoscope • Fig 3.7 • Continuously variable magnication of 2.5~10(5~20) power. • Image in each eyepiece  rotate 3600 • Expensive, precision, high resolution

  21. 3.3 Basic photo interpretation equipment (cont.) • Light table: • Fig 3.8 • For transparency • Balance the spectral characteristics of the film and lamps for optimum viewing condition • Color temperature 3500k  black body heat at 3500k • Noon daylight~5500k • Indoor tungsten bulb 3200k • Distance measurement • Low accuracy  cheaper • e.g. a triangular engineer’s scale or metric scale

  22. 3.3 Basic photo interpretation equipment (cont.) • Area measurement • Extremely accurate measurement • see §4.9, §4.10 • Direct measurement • Error sources  measuring device, relief, tilt  better to use vertical photos with low relief. • Dot grid (Fig 3.9) • Polar planimeter (Fig 3.10) • Electronic coordinate digitizer (Fig 3.11)

  23. 3.3 Basic photo interpretation equipment (cont.) • Interpretation information map • Different size (map and photo) • Zoom Transfer Scope (Fig 3.13) • Color additive viewer (Fig 2.42)

  24. 3.4 Land use/ land cover mapping • Land cover: • The type of feature present on the surface of the earth • Land use: • Human activity or economic function associated with a specific piece of land. • A knowledge of both land use and land cover can be important for land planning and land management

  25. 3.4 Land use/ land cover mapping (cont.) • USGS land use and land cover classification system • Land use and land cover should not be intermixed , but practically, land cover  land use • but also need some additional information sources • Use categories rather than specific information

  26. 3.4 Land use/ land cover mapping (cont.) • USGS land use and land cover classification system (cont.) • Designed criteria: • 85% accuracy • Same accuracy for the several categories • Repeatable from one time of sensing to another • Applicable over extensive areas • Infer land use

  27. 3.4 Land use/ land cover mapping (cont.) • USGS land use and land cover classification system (cont.) • Designed criteria (cont.) • Use for different time of a year • Divisible categories • Aggregation of categories • Comparison with future data • Recognize multiple uses of land

  28. 3.4 Land use/ land cover mapping (cont.) • USGS land use and land cover classification system (cont.) • Table 3.3: level I, II • Also provide level III IV, but it is intended to let the local users to design level III, IV. (Fig 3.14) • Reviewing and revising  more wetland classes • Table 3.4: Representative image interpretation formats for various classification levels. • General relationship, not restriction. • Minimum size of land use/land cover units mapped at various classification levels. • The smallest representative area on a map 2.5mm x 2.5mm.

  29. 3.4 Land use/ land cover mapping (cont.) • Level I classes • Urban or built-up land  take precedence • Agricultural land  drained wet lands for agriculture • Rangeland • Forest land  tree-crown areal density>10% • If has wet land characteristics  wet land category • Water

  30. 3.4 Land use/ land cover mapping (cont.) • Level I classes (cont.) • Wetland • Shallow water with submerged  vegetation water class • Short-lived wetness or flooding  wetland • Cultivated wetlands  agricultural land • Uncultivated wetland  wetland • Drained wetland for other purposes  other classes • Barren land: vegetation or other cover <1/3 • Tundra: treeless regions beyond the geographic limit of the boreal forest and above the altitudinal limit of trees in high mountain ranges. • Perennial snow or ice areas

  31. 3.4 Land use/ land cover mapping (cont.) • USGS land use/land cover classification system maps • 1:250,000 • For most categories: a minimum map unit 16 ha • Some  1:100,000 • Digital data: • vector format • raster format (grid cell size 4 ha)

  32. 3.5 Geologic and soil mapping • Complex and variable earth surface • Topographic relief and material composition • Reflect the bedrock, unconsolidated materials, agents of charge. • Rock type, fracture, effects of internal movement, erosion, • Bear the imprint of the processes that produced them

  33. 3.5 Geologic and soil mapping (cont.) • Geomorphological principles • Airphoto interpretation & geological and soil mapping • Identify and evaluate materials and structures. • Geological mapping • History of development: 1913, 1920, 1940….. • Identify landforms, rock types, rock structure, portray geological units and structure and spatial relationship. • explore mineral resource. • Far below the surface and inaccessible region • R.S.  potential area  drill holes

  34. 3.5 Geologic and soil mapping (cont.) • Geological mapping (cont.) • Multistage image interpretation: • 1:250,000, 1:100,000  1:58,000~1:130,000  1:20,000 • Lineaments: regional linear features  linear alignment of regional morphological features  streams, escarpments, mountain ranges, tonal features (fractures or fault zones). • Scales: a few ~ hundreds of km • Important in mineral resource studies  ore deposition • Detection  angular relationship. (Fig 3.16)

  35. 3.5 Geologic and soil mapping (cont.) • Geological mapping (cont.) • Ronchi grid • A diffraction grate: 78 lines/cm • || grid  suppressed •  grid  enhanced. • Lithologic mapping • The mapping of rock units • Stereoscopic viewing  enhance • See § 3.15

  36. 3.5 Geologic and soil mapping (cont.) • Geological mapping (cont.) • Geobotany • The relationship between a plant’s nutrient requirements and 2 interrelated factors– the availability of nutrients in the soil and the physical properties of the soil, including the availability of soil moisture indirect indicator • Distribution of vegetation  (indirect indicator)  composition of the underlying soil and rock materials • Geobotanical approach to geologic mapping  Cooperative effort among geologists, soil scientists and field-oriented botanists • Identification of vegetation anomalies related to mineralized areas.

  37. 3.5 Geologic and soil mapping (cont.) • Geological mapping (cont.) • Geobotany (cont.) • Geobotanical anomalies: • Anomalous distribution of species and/or plant communities • Sturted growth and/or decreased ground cover • Alteration of leaf pigment and/or physiographic process that produce leaf color changes. • Anomalous charges in the phenologic cycle. e.g. early foliage change senescence in the fall. alteration of flowering periods, late leaf flush • Taking photos several times during the year. Establishing “normal” condition  identify “anomalous” • Band 1.6 um & 2.2 um are important for mineral exploration and lithologic mapping.

  38. 3.5 Geologic and soil mapping (cont.) • Soil mapping • Soil survey  resource information  land use planning • Trained scientists + extensive field works + airphoto interpretation  identify soil & delineate soil boundaries. • Airphoto interpretation  1930s Panchromatic aerial photos: 1:15,840~1:40,000

  39. 3.5 Geologic and soil mapping (cont.) • Soil mapping (cont.) • Agricultural soil survey (Fig 3.17, Table 3.6) • USDA, 1900s. • 1957  publish • 1980s  many counties  line maps or digital form • Purposes: • Estimating crops • Evaluating rangeland suitability • Determine woodland productivity • Assessing wildlife habitat conditions • Judging suitability for various recreational uses • Judging suitability for various development uses

  40. 3.5 Geologic and soil mapping (cont.) • Soil mapping (cont.) • The reflection of sunlight from bare soil surfaces • Soil moisture content • Soil texture • Surface roughness • Iron oxide • Organic matter content

  41. 3.5 Geologic and soil mapping (cont.) • Soil mapping (cont.) • Plate 8: different appearance of one field during one growing season • Soil parent materials glacial meltwater deposits of stratified sand and gravel overlain by 45~150 cm of loess (wind-deposited silt) • (a), (b), (c): • corn plants 10 cm • 2.5 cm rain fall • uniform  patchiness • dry  high infiltration & slight mound • wet  low infiltration & receive runs off

  42. 3.5 Geologic and soil mapping (cont.) • Soil mapping (cont.) • Plate 8: (cont.) • (d), (e), (f): • corn plants 2m • little rain fall • dry  leaves and stalks drying out and turn brown. • wet  continuing to grow and still green • Soil scientist  four classes. (Fig 3.18 & Table 3.7) • Certain times of the year are better suited to aerial photography for soil mapping purposes than others.

  43. 3.6 Agricultural applications • Big picture direct application • Crop type classification (and area inventory) • Spectral response and photo texture identify crop type • Require a knowledge of the developmental stages of each crop in the area to be inventoried crop calendar • Use photographs taken on several dates during the growing cycle for crop identification • Color + infrared films are better than panchromatic film

  44. 3.6 Agricultural applications (cont.) • Crop type classification (cont.) • Stereoscopic coverage  plant height  discrimination • Table 3.8: dichotomous airphoto interpretation key use single-date panchromatic photography  only broad classes of crops are to be inventories. • Fig 3.19: demonstrate the importance of date of photography, photo tone and texture, and stereoscopic coverage.

  45. 3.6 Agricultural applications (cont.) • Crop condition assessment • Large scale airphotos  documenting deleterious conditions  crop disease, insect damage, plant stress, disaster damage. • Table 3.9: typical crop management information potentially obtainable from large scale color infrared aerial photographs.

  46. 3.6 Agricultural applications (cont.) • Crop condition assessment (cont.) • Detailed within field interpretations of soil and crop condition fertilizer spreaders and irrigators crop management activities  fn(geolocation) • Detected plant diseases • detected insect damage • other detected damage: • A difficult task  finer differences in spectral response

  47. 3.6 Agricultural applications (cont.) • Crop yield estimation • Simple & straightforward  area * yield/area  yield • Complex  soil moisture, soil fertility, air and soil temperature, disease, insect stress,….. • Crop yield prediction  climatic & meteorological conditions. • Traditional approach: area * yield/area (airphoto interpretation) (field inspection) • Direct approach  historical information  deviation

  48. 3.6 Agricultural applications (cont.) • Other applications • Determine areas  erosion control, weed control fertilizing, replanting, fencing or other remedial measures • Taxation & real estate purposes • Assessment of irrigation systems • Farm livestock surveys

  49. 3.7 Forestry applications • 1/3 of the world’s land area • Tree species identification • More complex than crop identification. • Complex mixture  more uniform • Forest understory • Step 1: elimination Step 2: establish groups Step 3: identify individual species • Shape & size • Fig 3.20: Silhouettes of forest trees • Fig 3.21: Aerial views of tree crowns. • Pattern & Shadows

  50. 3.7 Forestry applications (cont.) • Tree species identification (cont.) • Tone relative tones • Texture  tufted, smooth, billowy • Fig 3.22, Fig 3.23 • Black spruce • coniferous, slender crowns, pointed tops. • even height or change gradually • carpetlike appearance • Aspen • deciduous, rounded crowns • widely spaced, variable in size and density • Balsam fir • symmetrical coniferous, sharply pointed tops • thicker than black spruce • erratic changes in size  uneven and irregular pattern

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