Photogrammetry
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Photogrammetry is the technique of obtaining reliable spatial information about physical objects through analyzing photographs. It involves taking overlapping aerial photographs from an elevated position and processing them using software to extract 3D spatial data and produce accurate maps, models and measurements. The key outputs of photogrammetry include digital elevation models (DEMs), digital terrain models (DTMs), contour maps, orthophotos and 3D city models. Photogrammetry provides precise, cost-effective representations of geographic features and terrain.
Photogrammetry
- 1. PHOTOGRAMMETRY G.CHANDRA SEKHAR REDDY M.Tech(GIS) NIIT UNIVERSITY
- 2. VERY PRECISE 3D REPRESENTATION TIME EFFECTIVE COST EFFECTIVE BASED ON WELL ESTABLISHED AND TESTED ALGORITHMS LESS MANUAL EFFORT MORE GEOGRAPHIC FIDELITY
- 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. Aerial photography is the taking of photographs of the ground from an elevated position. The term usually refers to images in which the camera is not supported by a ground-based structure Close-range Photogrammetry the camera is close to the subject and is typically hand held or on a tripod
- 5. PROCESS FLOW RAW DATA FORM CLIENT (SCANS) AERIAL TRIANGULATION DATA CAPTURING DEM GENARATION CONTOUR GENARATION ORTHOPHOTO GENARATION
- 6. In Aerial Photogrammetry the camera is mounted in an aircraft and is usually pointed vertically towards the ground Multiple overlapping photos of the ground are taken as the aircraft flies along a flight path These photos are processed in a stereo-plotter
- 7. Adjacent but overlapping aerial photos are called stereo-pairs and are needed to determine parallax and stereo/3D viewing
- 9. Overlapping photography Endlap - ~60% Sidelap - ~20-30%
- 10. RASTER AND VECTOR DATA THE DATA PREPARATION PLANMETRIC FEATURES DATA OUTPUT
- 11. Raster data are described by a cell grid, one value per cell Vector Raster Point Line Zone of cells Polygon
- 12. Buildings Transportation Features Hydro Features Utilities Vegetation Breaklines DTM points Bridges
- 13. 1 3
- 14. Stereo Image Vector Data
- 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 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. 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
- 19. 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 of application 3D city models are focused on buildings however it may contain roads, green cover, trees etc. according to the usage of model
- 20. 3D BUILDING MODEL The constructed 3D model
- 21. Photogrammetry …. Lecture 11 Dr. Steve Ramroop
- 23. ORTHO PHOTO GENERATION Ortophotos are photographs that have been corrected for distortions Distortions from the camera lens, and relief To use these orthophoto images as a map, it is of great importance to provide orthophoto images in high level of accuracy
- 24. ORTHOIMAGE
- 25. ORTHOIMAGE location of bridges uncorrected and corrected for height differences against the road below
- 26. conclusion 3D Representation and Visualization of real world is only possible with photogrammetry.The output of photogrammetry is typically a map Many of the maps we use today are created with photogrammetry and photographs taken from aircraft.
- 27. THANK YOU
Editor's Notes
- #8: Wild,pan,awis,liss