Photogrammetry chandu

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Photogrammetry chandu

  1. 1. PHOTOGRAMMETRY G.CHANDRA SEKHAR REDDY M.Tech(GIS) NIIT UNIVERSITY
  2. 2.  VERY PRECISE 3D REPRESENTATION TIME EFFECTIVE COST EFFECTIVE BASED ON WELL ESTABLISHED AND TESTED ALGORITHMS. LESS MANUAL EFFORT MORE GEOGRAPHIC FIDELITY
  3. 3.  Photos – light Gramma – to draw Metron – to measure “Photogrammetry is the technique of measuring objects from photographs”“The art, science and technology of obtaining reliable spatial information about physical objects and the environment through the processes of recording, measuring and interpreting image data.”
  4. 4. Aerial Photogrammetry the camera is mounted in anaircraft and is usually pointed vertically towards theground. Multiple overlapping photos of the ground aretaken as the aircraft flies along a flight path. Thesephotos are processed in a stereo-plotter (an instrumentthat lets an operator see two photos at once in a stereoview). These photos are also used in automatedprocessing for Digital Elevation Model (DEM) creation.Close-range Photogrammetry the camera is close tothe subject and is typically hand held or on a tripod.Usually this type of photogrammetry work is non-topographic - that is the output is not topographicproducts like terrain models or topographic maps, butinstead drawings and 3d models. Everyday cameras areused to model buildings, engineering structures,vehicles, forensic and accident scenes, film sets, etc.
  5. 5. PROCESS FLOW=> RAW DATA FORM CLIENT=> AERIAL TRIANGULATION=> DATA CAPTURING=> DEM GENARATION=> CONTOUR GENARATION=> ORTHOPHO GENARATION=> GIS CONVERSTION
  6. 6. In Aerial Photogrammetry the camera is mounted inan aircraft and is usually pointed vertically towardsthe ground. Multiple overlapping photos of theground are taken as the aircraft flies along a flightpath. These photos are processed in a stereo-plotter(an instrument that lets an operator see two photos atonce in a stereo view).
  7. 7. AERIALTRIANGULATIONAeotriangulationadoptsphotogrammterictriangulation whichestablishes thegeometricrelationships amongoverlapping andsidelappingphotographs todeterminesupplementalhorizontal and verticalcontrol points
  8. 8.  Adjacent but overlapping aerial photos are called stereo-pairs and are needed to determine parallax and stereo/3D viewing
  9. 9.  Overlapping photography Endlap - ~60% Sidelap - ~20-30%
  10. 10. PLANIMETRIC FEATURE EXTRACTION
  11. 11.  Buildings Transportation Features Hydro Features Utilities Vegetation Breaklines DTM points Bridges
  12. 12. Raster data are described by a cell grid, one value per cell Vector Raster Point Line Zone of cells Polygon
  13. 13. 15
  14. 14. PLANMETRIC FEATURES
  15. 15.  There is no common usage of the terms digital elevation model (DEM), digital terrain model (DTM) and digital surface model (DSM) in scientific literature. In the most cases the term digital surface model represents the earths The digital terrain model represents the bare ground surface The term Digital Elevation Model is often used as a generic term for DSMs and DTMs, only representing height information without any further definition about the surface
  16. 16.  There is no common usage of the terms digital elevation model (DEM), digital terrain model (DTM) and digital surface model (DSM) in scientific literature. In the most cases the term digital surface model represents the earths The digital terrain model represents the bare ground surface The term Digital Elevation Model is often used as a generic term for DSMs and DTMs, only representing height information without any further definition about the surface
  17. 17.  Contour lines are lines drawn on a map connecting points of equal elevation Contour lines are useful because they allow us to show the shape of the land surface (topography) on a map This vertical spacing is referred to as the contour interval If the contour interval is 10 ft. Each the contour lines was a multiple of 10 ft.( i.e. 0, 10, 20, 30) In areas with high relief the contour interval is usually larger
  18. 18. DATA FOR THE 3D CITY MODELS The 3D city models contain data, which is related to the Spatial objects.Those objects are generally topography, buildings, transportation,plant cover, infrastructure and other details related to the goal ofapplication.3D city models are focused on buildings however it may containroads, green cover, trees etc. according to the usage of model.
  19. 19. 3D BUILDING MODEL The constructed 3D model
  20. 20. Photogrammetry …. Lecture 11 Dr. Steve Ramroop
  21. 21. ORTHO PHOTO GENARATION
  22. 22. ORTHO PHOTO GENARATIONUsually orthoimages do have some geometric limitations, they doshow only the elements located in the height level of the used DEM inthe correct location. Buildings not included in the DEM, are shifted withthe location of the roofs depending upon the tangent of the nadir angleof the image location multiplied with the building height. So also parts ofthe facade can be seen If the height value of the roof is included in adetailed DEM, the roof is shown in the correct position corresponding toan orthogonal map projection. This is causing the problem that for someparts, before hidden by the roof, no information is available for theorthoimage
  23. 23. ORTHOIMAGE location of a building in a usual orthoimage with theorthoimage based on a DEM the bare corrected location of including ground the building roof
  24. 24. ORTHOIMAGElocation of bridges uncorrected and corrected forheight differences against the road below
  25. 25.  The output of photogrammetry is typically a map, drawing or a 3d model of some real- world object or scene. Many of the maps we use today are created with photogrammetry and photographs taken from aircraft.

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