Introduction to aerial photography and

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  1. 1. Introduction to Aerial Photography and Photogrammetry T.SrinivasaRao
  2. 2. Study of Aerial photography - Whether it may be photogrammetry or interpretation - is subset of a large discipline called "Remote Sensing"
  3. 3. What is Remote Sensing? Remote sensing is the science and art of obtaining information about an object, area, or phenomenon through the analysis of data acquired by a device that is not in contact with the object, area, or phenomenon under investigation
  4. 4. Aerial Photography The term "photography" is derived from two Greek words meaning "light" (phos) and "writing" (graphien). Photography is production of permanent images by means of the action of light on sensitized surfaces (film or array inside a camera), which finally giving rise to a new form of visual art. Aerial Photography means photography from the air
  5. 5. Aerial Photography Aerial Photography is one of the most common, versatile and economical forms of remote sensing. It is a means of fixing time within the framework of space (deLatil, 1961). Aerial photography was the first method of remote sensing and even used today in the era of satellite and electronic scanners. Aerial photographs will still remain the most widely used type of remote sensing data.
  6. 6. 1858 - Gasper Felix Tournachon "Nadar" took the first aerial photograph from a captive balloon from an altitude of 1,200 feet over Paris. Aerial Photography
  7. 7. Aerial Photography
  8. 8. Aerial Photography
  9. 9. 1908, Julius Neubronner
  10. 10. Between 1887 and 1889, Arthur Batut took aerial shots of the South of France using just a kite, a camera. 1887 and 1889, Arthur Batut
  11. 11. Aerial photography Between 1887 and 1889, Arthur Batut took aerial shots of the South of France using just a kite, a camera. In 1908, Julius Neubronner, who had used carrier pigeons in his work as an apothecary, filed a patent for a miniature camera that could be worn by a pigeon and would be activated by a timing mechanism. Pigeons were also used by the French to capture the position of the German army in the First World War. Ref: utm_source=tny&utm_campaign=generalsocial&utm_medium=facebook&mbid=social_facebook
  12. 12. Characteristics of Aerial Photography 1. Synoptic Viewpoint: Aerial photographs give a bird's eye view of large areas enabling us to see surface features in their spatial context. They enable the detection of small scale features and spatial relationships that would not be found on ground.
  13. 13. Characteristics of Aerial Photography 2. Time freezing ability: They are virtually permanent records of the existing conditions on the Earths surface at one point in time, and used as an historical document. 3. Capability to stop action: They provides a stop action view of dynamic conditions and are useful in studying dynamic phenomena such as flooding, moving wildlife, traffic, oil spills, forest fires
  14. 14. Characteristics of Aerial Photography 4. Three dimensional perspective: It provides a stereoscopic view of the Earths surface and make it possible to take measurements horizontally and vertically - a characteristic that is lacking for the majority of remotely sensed data. 5. Spectral and spatial resolution: Aerial photographs are sensitive to radiation in wavelengths that are outside of the spectral sensitivity of the human eye (0.3 m to 0.9 m versus 0.4 m to 0.7 m).
  15. 15. Characteristics of Aerial Photography 6. They are sensitive to objects outside the spatial resolving power of human eye. 7. Availability: Aerial photographs are readily available at a range of scales for much of the world. 8. Economy: They are much cheaper than field surveys and are often cheaper and more accurate than maps.
  16. 16. Photogrammetry - Introduction Photogrammetry is the science and technology of obtaining spatial measurements and other geometrically reliable products from photographs.
  17. 17. Photogrammetry - Introduction The principal application of photogrammetry is to determine the spatial position of the natural and man- made features situated on the earth's surface (topographic application). Photogrammetry is also used as a measuring tool in architecture, industrial design, deformation studies of structures, accident investigation, medicine etc. These operations are referred to as non-topographic applications.
  18. 18. Photogrammetry - Introduction Based on the location of sensor Terrestrial photogrammetry: Images aquired by a ground based stationary sensor close range photogrammetry: Sensor present in close vicinity to the target object. Aerial photogrammetry: Sensors mounted on airborne platforms Space photogrammetry: Mounted on satellites
  19. 19. Methods for photogrammetric measurements and processing data Method 1: Requires complex instruments, which physically model the geometric relationship between the image and object at the time of data acquisition. These instruments act as analogue computers and the method is called as analogue or instrumental photogrammetry.
  20. 20. Methods for photo..contd..! Method 2: Photogrammetric operations are performed by mathematical modelling. This method is called analytical, numerical or computational photogrammetry. The use of digital images is a special case here. And because of the wide range of data processing techniques available and the type of instrumentation used here this class is called as digital or softcopy photogrammetry.
  21. 21. Objectives and priciples of surveying adheres well with the photogrammetric principles and hence, the images acquired using photogrammetric principles can be used for surveying complementing the on- site surveys.
  22. 22. Imaging has distinct advantages over data acquisition by direct, on-site, measurement.: An image is a complete, comprehensive record of a scene or situation as it existed at the instant of acquisition. It is a multilevel data set which can provide both quantitative and qualitative information. Data acquisition can be accomplished within a short time over large areas by imaging from the air or space. Processing and analysis of this data can be made at an appropriate time and place, .distant from the scene and can be repeated or augmented at will. The direct observation of directions and distances means point-by- point measurement, while on images continuous measurements can be made by tracing or delineating objects.
  23. 23. The weather and the seasons can place severe restrictions on the primary data acquisition. On the other hand, under favorable conditions, images can be acquired over a large tract of land within a short period oftime from the air or from space. It is not feasible to use aerial photography for the survey of small areas. Equipment needed for the acquisition and processing of the data is more expensive and more complex to operate than those used for surveying on site. Photogrammetry is not an entirely selfsufficient spatial positioning process. A certain amount of on-site observations are needed to control and verify the analysis. At the current state of the art, direct in situ measurements can provide the highest possible accuracy for determining spatial positions. Disadvantag es
  24. 24. Applications of photogrammetry Topographical mapping: The plotting of map detail and contours is normally carried out using aerial photogrammetric methods These methods are used for both original survey and revision, and replace classical ground methods except where the task is so small that flying is uneconomical The technique needs a certain amount of ground surveyed control, but this requirement is being continually reduced with the improvement of aerial triangulation techniques to provide supplementary control. A final Field check is necessary
  25. 25. Applications of photogrammetry Large Scale Plans: Large scale plans can be produced accurately and quickly by air survey methods, but requires thorough checking. For large tasks such as road building and major constructions, air survey methods are quicker and cheaper than ground methods. profiles for determination of earthwork quantities can be simply obtained using aerial photographs.
  26. 26. Land use maps Hydrographic maps: mapping coast lines etc., Exploration and reconnaissance Terrestrial and Scientific uses Detailed surveying of historic buildings Traffic accidents Medical applications etc., Stereoscopic applications and measurements
  27. 27. Applications of photogrammetry Cadastral Maps: Similar types advantages compared to large scale maps can be gained here. Ground techniques are accurate but not required in all cases. Air photo techniques provides necessary information with adequate accuracy.