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Introduction of photogrammetry

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Introduction of photogrammetry

  1. 1. PPhhoottooggrraammmmeettrryy II Introduction to Photogrammetry S.M.J.S.Samarasinghe Superintendent of Surveys Institute of Surveying and Mapping Diyatalawa- Sri Lanka
  2. 2. LLeeccttuurree OOuuttlliinnee • Introduction to Photogrammetry: History of the development of Aerial Surveying. The Geometry of the titled photography. • The characteristics of the Aerial Camera, Auxiliary equipment used in aerial Photography. Photographic mission planning. Understanding aerial photograph (Principle information etc…). Principles of stereoscopic vision, definition of parallax, the basic parallax formula. • Stereoscopic Viewing methods, Distortions in a field photograph.
  3. 3. LLeeccttuurree OOuuttlliinnee •Geometry of stereo pairs, Theory of orientation: Inner orientation, Relative orientation, Absolute orientation. •Problems in relative orientation due to topography. •Photogrammetric plotting Instruments (Analogue). Ground control. •Model Deformation. Numerical Relative Orientation. •Photographic coordinate system. Mono comparator, Stereo comparator measurements of photo coordinates, Transformation. •Elementary methods of planimetric mapping with vertical photographs. Field compilation and map making.
  4. 4. TTeexxtt BBooookk Elements of Photogrammetry- Second edition , Author: Paul R. Wolf
  5. 5. AAccttiivviittiieess Lecture Hours 30 Practical & Tutorial Hours 15 Final Exam 80% Assignments and quizzes 20% 100% GGrraaddee PPoolliiccyy EEvvaalluuaattee
  6. 6. Introduction
  7. 7. Definitions: DDeeffiinniittiioonn Remote Photogrammetry ”The science or art of obtaining reliable measurements by means of photographs.” ”Photogrammetry is the art, science, and technology of obtaining reliable information about physical objects and the environment through the processes of recording, measuring, and interpreting photographic images and patterns of electromagnetic radiant energy and other phenomena.” (ASPRS, 1980)
  8. 8. Why Photogrammetry……… RAF's wartime reconnaissance photos -archive Dramatic pictures illustrate Allied assault on D-Day and bombing raids over Germany
  9. 9. Photogrammetry……… Analog PPhhoottooggrraammmmeettrryy Using optical, mechanical and electronical components, and where the images are hardcopies. Re-creates a 3D model for measurements in 3D space. AAnnaallyyttiiccaall PPhhoottooggrraammmmeettrryy The 3D modelling is mathematical (not re-created) and measurements are made in the 2D images. DDiiggiittaall PPhhoottooggrraammmmeettrryy Analytical solutions applied in digital images. Can also incorporate computer vision and digital image processing techniques. or Softcopy Photogrammetry ”Softcopy” refers to the display of a digital image, as opposed to a ”hardcopy” (a physical, tangible photo).
  10. 10. Photograph Image A scene which was detected as well as recorded on film. A scene which was detected electronically. Chemical reactions on a light sensitive film detects the intensity of the incoming energy. Generate an electrical signal proportional to the incoming energy. Simple, cheap, well known. Can sense in many wavelengths, data can be easily converted into digital form for automated processing. Only sense in the wavelength of 0.3 – 0.9 μm, manual interpretation. Complex, Expensive sensors Photograph vs. Image
  11. 11. Relationships of the Mapping Sciences as they relate to Mathematics and Logic, and the Physical, Biological, and Social Sciences
  12. 12. History
  13. 13. HHiissttoorryy History of Aerial Photography:
  14. 14. HHiissttoorryy Origins of Remote Sensing Remote sensing began with aerial photography First photographs taken in 1839
  15. 15. HHiissttoorryy Paris by Nadar, circa 1858 1858 Gasper Felix Tournachon "Nadar" takes photograph of village of Petit Bicetre in France from a balloon.
  16. 16. HHiissttoorryy Boston by Black and King (1860)
  17. 17. HHiissttoorryy World War One was a major impetus to development of aerial photography
  18. 18. HHiissttoorryy After the war the technology was in place to begin large scale aerial surveys
  19. 19. A brief history of Photogrammetry
  20. 20. A brief history of Photogrammetry
  21. 21. A brief history of Photogrammetry
  22. 22. Why Photogrammetry……… Measuring values and camera constants
  23. 23. Why Photogrammetry •Extracting geometrical information and producing maps. •Cheaper than terrestrial methods. •Extracting qualitative information. •High speed of map generation.
  24. 24. Why Photogrammetry……… Ideal technology when measuring objects such as – Vast regions to be mapped – Irregular shapes and – Objects that are too • Hot or cold • Soft • Delicate • Inaccessible • Toxic • Radioactive to touch
  25. 25. Photogrammetric products Planimetric maps – Planimetric elements in geography are those features that are independent of elevation, such as roads, building footprints, and rivers and lakes. They are represented on two-dimensional maps as they are seen from the air, or in aerial photography. These features are often digitized from orthorectified aerial photography into data layers that can be used in analysis and cartographic outputs. Topographic maps – A type of map characterized by large-scale detail and quantitative representation of relief, using contour lines. Traditional definitions require a topographic map to show both natural and man-made features. A topographic map is typically published as a map series.
  26. 26. Photogrammetric products…… 3D points LiDAR has become the technology of choice for deriving highly accurate terrain data and 3D models, and it is commonly used for a variety of mapping applications.
  27. 27. Photogrammetric products…… Photomap (Orthophotos) DEM/ DTM DSM
  28. 28. General Process
  29. 29. General Flow Real World (Earth) Sensor (Camera) Data Source (Images) Image Refinement & measurement Refined Image Observation Products •Maps •DEM •Otrthophoto Mathematica l Models Decision Making Data Analysis
  30. 30. Production Line Mapping Using Aerial Photogrammetry
  31. 31. Photogrammetric Types
  32. 32. Photogrammetric Types Photogrammetric Types from Applications Point of View (d is distance from camera to object)  Close Range Photogrammetry d<10 m  Terrestrial Photogrammetry 10 m<d<100 m  Aerial Photogrammetry 2 km<d<10 km  Space Photogrammetry 30 km<d
  33. 33. Close Range Photogrammetry
  34. 34. Terrestrial Photogrammetry  Taken with ground-based cameras  Position and orientation often measured
  35. 35. Terrestrial Photogrammetry
  36. 36. Aerial Photogrammetry
  37. 37. Space Photogrammetry  Extraterrestrial pictures taken from space-based cameras
  38. 38. Space Photogrammetry  Extraterrestrial Spot Image
  39. 39. Space Photogrammetry  Extraterrestrial NOAA Image
  40. 40. Space Photogrammetry  Extraterrestrial Ikonos Image
  41. 41. Types of Images • Panchromatic, Black & White, Grayscale • Color RGB • Multispectral • Hyperspectral
  42. 42. Panchromatic Image
  43. 43. Black and white Image
  44. 44. Grayscale Image
  45. 45. True Color composite image
  46. 46. False Color composite image
  47. 47. Types of photographs (categorized by tilt) • Vertical - camera axis as nearly vertical as Possible • Oblique - camera axis intentionally tilted • Low Oblique • High Oblique
  48. 48. Types of photographs Aerial Terrestrial Vertical Oblique Truly Vertical High oblique (includes horizon) Tilted (1deg< angle < 3deg) Low oblique (does not include horizon)
  49. 49. Vertical Aerial Photogrammetry  Mainly used for mapping
  50. 50. Low Oblique Low oblique (no horizon)
  51. 51. High Oblique • Horizon line in the photo
  52. 52. Vertical aerial images are not map! • Maps are based on parallel projection while photo has central projection • Maps have a unique scale while image scale varies depending on terrain relief • Maps are interpreted while photos should be interpreted • Photo is detailed while maps are generalized
  53. 53. 53/89 Projection systems
  54. 54. Taking photographs
  55. 55. Taking Vertical Aerial Photographs • Photos taken in parallel flight strips
  56. 56. Taking Vertical Aerial Photographs • Each successive photograph overlap previous photo
  57. 57. Forward Overlap (End Lap)
  58. 58. Aerial Photography Stereo pair •Over lap about 60%
  59. 59. Aerial Photography – Stereo pair •Over lap about 60% •Aerial Base: the distance between two successive projection centers
  60. 60. Side Overlap (Side Lap)
  61. 61. Taking Vertical Aerial Photographs • Position of camera at each exposure called exposure station • Flying height – altitude of camera • Adjacent flight strips overlap – side overlap • Block of photos – photos of 2 or more side lapping strips
  62. 62. Block of photographs
  63. 63. Projection Plotters
  64. 64. Direct Optical PPrroojjeeccttiioonn SStteerreeoo ppllootttteerrss  MULTIPLEX MODEL SKETCH
  65. 65. Direct Optical PPrroojjeeccttiioonn SStteerreeoo ppllootttteerrss  Nistri Photomultiplex Model D III  Kelsh Stereoplotter
  66. 66. Direct Optical PPrroojjeeccttiioonn SStteerreeoo ppllootttteerrss  Kern PG-2 analog stereo-plotter.
  67. 67. Direct Optical PPrroojjeeccttiioonn SStteerreeoo ppllootttteerrss  Kern PG-3 analog stereo-plotter, Switzerland
  68. 68. Direct Optical PPrroojjeeccttiioonn SStteerreeoo ppllootttteerrss  Wild A-10 analog stereo-plotter.
  69. 69. DDiiggiittaall ssyysstteemmss  Digital systems require that the aerial photographs be scanned as high-resolution images.
  70. 70. END

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