Ge 178 lecture 7 (flight planning)

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Ge 178 lecture 7 (flight planning)

  1. 1. GE 178 Lecture 7: Flight PlanningDepartment of Geodetic EngineeringUniversity of the Philippines Diliman jldfabila ’09 japrincipe ‘10
  2. 2. Project Planning• Successful execution of any photogrammetric project requires thorough planning• Must first determine the selection of products to be prepared, their scales and accuracies aerial photo prints, photo indexes, photomaps, mosaics, orthophotos, planimetric maps, topographic maps, cadastral maps, digital maps, digital elevation models
  3. 3. Project PlanningAfter the product selection process, – Planning the aerial photography – Planning the ground control – Selecting instruments and procedures necessary to achieve the desired results – Estimating costs and delivery schedules
  4. 4. Flight Planning• Success of photogrammetric project depends on acquisition of good quality pictures• Due to weather and ground conditions, time frame for photography is limited• Reflights are expensive and causes long delays on project• Mission must be carefully planned and executed according to flight plan• Consists of flight map, (where photos should be taken) and specifications
  5. 5. Specifications• Camera requirements• Film requirements• Scale• Flying height• End laps, side laps• Tilt and crab tolerances
  6. 6. Stereopair• Each photo covers partially the same area overlap photo 1 photo 2
  7. 7. Neatmodel• Area of the overlap bounded by the principal points of the consecutive photographs overlap Neat model photo 1 photo 2
  8. 8. Overlap• Forward overlap or End lap – Common area covered by two successive photos of the same flight line or strip – Usually 60% ± 5%• Lateral overlap or Side lap – Common area covered by two adjacent flight lines/strips – About 25-30% ± 10% (generally 30%)
  9. 9. Overlap Direction of flight Forward overlap/Endlap Lateral overlap/SidelapFlight lines
  10. 10. Forward Overlap• If stereoscopic coverage is required, 50% is absolute minimum• To prevent gaps due to crab, tilt, flying height variations, terrain variations, >50% end lap is required• For photogrammetric control extension, points must be seen on at least 3 photos
  11. 11. Side Lap• Required to prevent gaps between flight strips• Using side laps >30% eliminates the need t ouse extreme edges of photo• Crab – disparity in the orientation of camera in the aircraft with respect to aircraft’s actual travel direction; causes the edges of the photo to be unparallel to direction of flight; reduces stereoscopic coverage• Drift – failure of the pilot to fly along planned flight lines
  12. 12. Flight Plan• What the aircrew has to do as indicated by flight lines• The design of aerial photography flight in order to obtain desired photos at a certain scale, i.e., how the air crew will fly (where to put the flight lines, how high, etc.)
  13. 13. Rules in determining flight line direction• Generally follows four cardinal directions – East-West (E-W) or North-South (N-S)• Should be along the longer dimension of the area• If over mountain ridges or valleys, go along the direction of the features – to maintain an almost constant scale; if a flight line crosses mountains, scale will be smaller in the valley than in the mountains
  14. 14. Direction of Flight Lines
  15. 15. Flight lines along the valley Cordillera Sierra Madre
  16. 16. Weather ConditionsFlight crew should be able to interpret weather conditions and make sound decisions on whether to fly or not• Ideally cloud free; < 10% cloud cover acceptable• Clouds higher than the flying height might cast large shadows on the ground• Overcast weather might be more favorable when large-scale topo mapping is done over built-up areas, forests, canyons or other features which cast shadows on clear sunny days• Photos for industrial areas susceptible to atmospheric haze, smog, dust and smoke are best taken after heavy rains• Windy days might cause excessive image motion and difficulties in camera and aircraft orientation
  17. 17. Required Data for Flight Planning• Project area boundary• Camera focal length – 3.5”, 6”, or 12”• Photoformat size – standard is 9” or 23 cm• Photoscale• Overlap requirements (in percentage) – percentage of endlap or sidelap• Least number of flight lines To be more• Least number of exposures economical
  18. 18. Flight Planning Computations• Flying height• Distance between exposures or Airbase (B)• Distance between flight lines• Total number of exposures• Flying height above mean sea level of each flight line• Total time needed for photography
  19. 19. s = photoformat/sizef = focal lengthHmge = flying height above sm.g.e.o = overlap in % fS = equivalent grounddistance of photoformat Hmge o S
  20. 20. Flying HeightH mge  f  s p
  21. 21. Distance Between Exposures Dexp  De  S 1  f .o.Where:S = equivalent ground length of the photoformatsize (s)S = (sp)(s)f.o. = forward overlap (in decimals)s = photoformat sizesp = photoscale factor
  22. 22. Distance Between ExposuresExample:Given: scale = 1:15,000 f.o. = 60% s.l. = 30% s = 9” = 23 cmRequired: De
  23. 23. Distance Between ExposuresSolution: De  (15,000)(23)(1  0.60) De  138,000 cm  1,380 m De  1.38 km
  24. 24. Distance Between Flight Lines D fl  D f  S 1  s.l.Where:S = equivalent ground length of the photoformatsize (s)S = (sp)(s)s.l. = sidelap (in decimals)s = photoformat sizesp = photoscale factor
  25. 25. Distance Between Flight LinesExample:Given: scale = 1:15,000 f.o. = 60% s.l. = 30% s = 9” = 23 cmRequired: Df
  26. 26. Distance Between Flight LinesSolution: D f  (15,000)(23)(1  0.30) D f  241,500 cm  2,415 m D f  2.42 km
  27. 27. Total Number of Exposurestotal number of exposures   number of exposures per flight line    number of flight lines 
  28. 28. Total Number of ExposuresWhere: longer dimensionnumber of exposures per f.l.  De longer dimension  B shorter dimensionnumber of flight lines  Df shorter dimension  W
  29. 29. Flying Height of Each Flight Line (above Mean Sea Level) H msl  H mge  m.g.e
  30. 30. Total Time of Photography  De t      number of exposures per f.l.  v    number of flight lines Where:  De t     time between exposures  v 
  31. 31. Total Time of PhotographyExample:Given: scale = 1:15,000 f.o. = 60% s = 9” = 23 cm average velocity of aircraft = 300 kph 20 exposures per flight line 10 flight linesRequired: t
  32. 32. Total Time of PhotographySolution: De  (15,000)(23)(1  0.60) De  138,000 cm  1,380 m  1.38 km  1.38  t    20 10  0.92 hrs  300  t  55.2 min
  33. 33. ExampleA project area is 16 km long in the east-west direction and 10.5 km in the north-south direction. Aerial photography of scale 1:12,000 will be used with end lap and side lap of 60% and 30%, resp. A 6-in focal length camera and a 23-cm square photo format is to be used.Prepare the: – flight map on a 1:24,000 base map – compute the total number of photographs needed
  34. 34. Solution• Equivalent ground distance of the photo format and distance between flight lines S  23 cm *12,000  2760 m D f  S (1  s.l.)  1932 m• Align the first and last flight lines with 0.3S (side lap dimension) coverage outside the north and south project boundary lines
  35. 35. Solution• Distance of the first and last flight lines inside North and South boundaries: 0.5S  0.3S  0.2S  0.2 * 2760 m  552 m• Number of spaces between flight lines: width  2 * 0.2S   4.9 round up to 5 Df• Number of flight lines: number of spaces  1  6
  36. 36. Solution• Adjust the percent side lap (for integral # of flight lines)  s.l.   s.l.  2 0.5   S  # of spaces 1  S  project width  100   100   s.l.   s.l.  2 0.5   2760 m  5 1  2760 m  10500 m  100   100  s.l.  31.4%• Adjust spacing Df:  31.4  D f  1  S  1893.4 m  100 
  37. 37. Solution• Distance between exposure De:  60  De  1  S  1104 m  100 • # of photos per strip (take 2 extra photos at both ends): 16000 m   1  2  2  19.5 (use 20) 1104 m
  38. 38. Solution• Total # of photos:  ( photos per strip)(# of flight lines )  (20)(6)  120• Spacing of flight lines on map: 1893.4  100  7.9 cm 24000
  39. 39. END OF LECTURE

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