1. Photogrammetry 1 آ. رحمانی زاده 1 فصل 11 : برنامه ريزي پرواز (پروژه) 50 Slides

2. Photogrammetry 1 آ. رحمانی زاده 2 Considerations In Planning What products will be prepared Scales Accuracies Meetings with client important in understanding client’s needs

3. Photogrammetry 1 آ. رحمانی زاده 3 General Planning Categories Planning aerial photography Planning ground control Selecting instruments and procedures to achieve desired results Estimating costs and delivery schedules

4. Photogrammetry 1 آ. رحمانی زاده 4 Ground Control For Photogrammetry Photogrammetric control - point whose position is known in object space and whose image can be positively identified on photography Provides means for orienting or relating photographs to ground

5. Photogrammetry 1 آ. رحمانی زاده 5 Photogrammetric Control Must satisfy 2 requirements: Must be sharp, well defined, and positively identified on all photos Must lie in favorable locations Normally conducted after photography acquired to satisfy requirements Ensure control does not fall in shadowed areas on some photos

6. Photogrammetry 1 آ. رحمانی زاده 6 PHOTOGRAMMETRIC CONTROL (Cont.) Horizontal control Images must be very sharp and well defined horizontally Samples: intersections of sidewalks, manhole covers, intersection of roads... Vertical control Well defined vertically Samples: small flat or slightly crowned areas with some feature nearby

7. Photogrammetry 1 آ. رحمانی زاده 7 Flight Planning Flight map Shows where photos are to be taken Specifications – how the photos will be taken Camera and film requirements Scale Flying height End and side lap Tilt and crab tolerances

8. Photogrammetry 1 آ. رحمانی زاده 8 End Lap And Side Lap End lap – overlapping successive photos Side lap – overlapping adjacent flight strips

9. Photogrammetry 1 آ. رحمانی زاده Flight Planning

10. Photogrammetry 1 آ. رحمانی زاده FLIGHT PLANNING

11. Photogrammetry 1 آ. رحمانی زاده 11 END LAP AND SIDE LAP (Cont.) Percent end lap: Normally taken as 60% Percent side lap: Normally about 30% Excessive drift most common cause for gaps in coverage

12. Photogrammetry 1 آ. رحمانی زاده عوامل كاهش پوشش طولي و عرضي  انحراف هواپيما از خط پرواز كه شامل دو پارامترdrift و Crab مي باشد.  تغييرات ارتفاع پرواز  وجود تيلت در عكس هاي هوائي  تغييرات ناهمواري زمين 12

13. Photogrammetry 1 آ. رحمانی زاده 13 Loss Of Stereoscopic Coverage Due to tile Due to unequal flying heights

14. Photogrammetry 1 آ. رحمانی زاده 14 LOSS OF STEREOSCOPIC COVERAGE (Cont.) Due to terrain variations

15. Photogrammetry 1 آ. رحمانی زاده 15 END LAP AND SIDE LAP (Example.) Example : Air base of a stereopair is 1400 m and flying height above average ground is 2440 m. Camera has a 152.4 mm focal length and 23-cm format. What is the percent end lap?

16. Photogrammetry 1 آ. رحمانی زاده 16 END LAP AND SIDE LAP (Solution.) Solution: Average scale: Ground coverage: Percent end lap:

17. Photogrammetry 1 آ. رحمانی زاده 17 END LAP AND SIDE LAP (Example.) Example: Assume spacing between adjacent flight lines is 2500 m in the previous example. What is the percent side lap? Solution:

18. Photogrammetry 1 آ. رحمانی زاده 18 Purpose Of Photography Metric qualities vs. Pictorial qualities For topographic mapping & other quantitative operations Prefer wide or super-wide-angle camera Large B/H’ ratio Larger B/H’ – greater parallactic angles between intersecting light rays Errors Increase with increasing flying height Decrease with increasing x parallax

19. Photogrammetry 1 آ. رحمانی زاده 19 Purpose Of Photography (Cont.) Parallactic angles increase with increasing B/H’ ratios

20. Photogrammetry 1 آ. رحمانی زاده 20 Purpose Of Photography (Cont.) For mosaics – relief displacement, tilt displacement & scale variation degrade pictorial qualities Minimized by decreasing B/H’ ratio Increase flying height reduces scale but can use longer focal length camera

21. Photogrammetry 1 آ. رحمانی زاده 21 Scale determined by altitude and focal length Scale and film format determines ground coverage for each frame Ground coverage = scale / film format Photo Scale

22. Photogrammetry 1 آ. رحمانی زاده 22 Photo Scale For topographic mapping – dictated by required scale of map and accuracy Example: Using aerial photos to study centerline markings. Actual width of painted centerline is 100 mm (4”). A high-resolution (80 line pair per millimeter) film used. What is minimum photo scale required?

23. Photogrammetry 1 آ. رحمانی زاده 23 Photo Scale (Cont.) Solution: Smallest object size: Minimum scale:

24. Photogrammetry 1 آ. رحمانی زاده 24 Photo Scale (Cont.) 5-6 times enlargement ratios common Example (18-4): A map will be compiled at a scale of 1:6,000. What is the photo scale if a 5 times enlargement will be used? Solution

25. Photogrammetry 1 آ. رحمانی زاده 25 Photo Scale (Cont.) Optimal scale important If larger than necessary – uneconomical If too small – reduces usefulness or may make it unsatisfactory Assume point to be plotted correctly within 1/30” with accuracy of 2’ Required map scale: If 5 times enlargement:

26. Photogrammetry 1 آ. رحمانی زاده 26 C-factor Empirical measure of contouring accuracy of a stereoplotter Defined as: Sometimes C-factor stretched for economical purposes

27. Photogrammetry 1 آ. رحمانی زاده 27 Some C-factor Values InstrumentC-Factor CommercialC-Factor Government Analytical Plotter30002500 Zeiss Planimat24002100 Wild A1024002100 Wild AG120001800 Wild A820001800 Kern PG220001800 Kelsh15001200

28. Photogrammetry 1 آ. رحمانی زاده 28 Compatible Map Scales & Contour Intervals For Average Terrain Imperial UnitsSI Units S Map CIS Map CI 1”=50’1’1:5000.5 m 1”=100’2’1:10001 m 1”=200’5’1:20002 m 1”=500’10’1:50005 m 1”=1000’20’1:1000010 m

29. Photogrammetry 1 آ. رحمانی زاده 29 Photo Scale Example: A topographic map has a scale of 1”=200’ with a 5’ contour interval is to be compiled on a stereoplotter having a nominal 6” focal principal distance. Determine the flying height for the photography if the maximum values for the C-factor and enlargement ration are 1500 and 5 respectively.

30. Photogrammetry 1 آ. رحمانی زاده 30 Solution: Using C-factor and contour interval H'=(C − factor)(CI)= 1500(5')= 7,500' Using enlargement ratio The lower flying height controls = 6,000’ Photo Scale (Cont.) 5

31. Photogrammetry 1 آ. رحمانی زاده 31 Photo Scale (Cont.) If contours not being used, spot elevations taken over model Rule of thumb: Ratio of flying height above ground to the accuracy to which spot elevations can be reliably read is ~ 5000 Example: If spot heights are to be accurate to ± ½ m, then

32. Photogrammetry 1 آ. رحمانی زاده 32 Computed Photo Scale C-factor should be used only under following conditions (Thorpe) 6” focal length camera Instrument in good calibration Good experienced operator Full vertical ground control Sharp, clear diapositives Smooth-sloped terrain Terrain unobscured by vegetation CPS – Computed Photo Scale - alternative

33. Photogrammetry 1 آ. رحمانی زاده 33 Computed Photo Scale (Cont.) Defined as: CI = contour interval, in feet CF = C-factor of instrument CA = camera’s maximum radial distortion 1.0 if distortion less than 5 μm 0.95 for distortions between 5 and 10 μm 0.90 for distortions greater than 10 μm

34. Photogrammetry 1 آ. رحمانی زاده 34 Computed Photo Scale (Cont.) FL = focal length 1.1 if f = 3 ½” 1.0 if f = 6” 0.75 if f = 8 ¼” 0.5 if f = 12” IN = instrument condition 1.0 for excellent calibration 0.9 for average calibration MB = maximum number of models bridged

35. Photogrammetry 1 آ. رحمانی زاده 35 Computed Photo Scale (Cont.) AN = analytical triangulation 1.0 for full ground control 0.9 for simultaneous bundle adjustment with additional parameters 0.85 for simultaneous bundle adjustment without additional parameters 0.8 for independent model 0.7 for polynomial adjustment OP = operator 1.0 for excellent operator 0.9 for average operator

36. Photogrammetry 1 آ. رحمانی زاده 36 Computed Photo Scale (Cont.) Example: Area to be mapped with 2’ contour interval using a 6” focal length camera having a maximum radial distortion of 8μm, with mapping on a Kelsh plotter in average condition with an excellent operator, using analytics developed from a polynomial adjustment method, bridging over 3 models Solution Photo scale is 1:3052

37. Photogrammetry 1 آ. رحمانی زاده Flight Planning Regardless of format, area coverage normally requires many photos

38. Photogrammetry 1 آ. رحمانی زاده FLIGHT PLANNING Number of frames required = the distance to be covered divided by the effective forward coverage. Time interval between exposures = the effective forward coverage divided by the aircraft ground velocity Photo runs are aligned using transferred principal points.

39. Photogrammetry 1 آ. رحمانی زاده FLIGHT PLANNING Data required include: Run Number Frame number Altitude Focal length Time Data included on photographic strip

40. Photogrammetry 1 آ. رحمانی زاده FLIGHT PLANNING

41. Photogrammetry 1 آ. رحمانی زاده 41 محاسبه تعداد عکسها و باندهاي مورد نياز در يک منطقه عکسبرداري تعداد عکسها در يک باند تعداد باندها در منطقه عکسبرداري = تعداد کل عکسها

42. Photogrammetry 1 آ. رحمانی زاده Aircraft Used These usually need to be slow and stable so often older types of aircraft are used, e.g. Dornier with a ceiling (maximum flying height) of 15,000ft and maximum speed of 120 knots (nautical miles per hour). The biggest aircraft used for survey photography are twin engine propeller planes, e.g. Rockwell Grand Commander with a ceiling of 33,000ft and maximum speed of 180 knots. The conditions inside are usually very cramped with one or two large cameras sitting in the middle pointing downwards. 42

43. Photogrammetry 1 آ. رحمانی زاده Aircraft Used High wing aircraft are preferable because of better visibility, (downward visibility is poor even with high wing aeroplanes). The Ordnance Survey hire aircraft for their survey work. One such is the Piper Navaho with 2 cameras - one with a 150 and one with a 305mm lens cone. 43

44. Photogrammetry 1 آ. رحمانی زاده Weather This is obviously very important. It is useless flying when there is low cloud cover blocking the ground view. The angle of the sun is important. Less than 30° solar latitude results in shadows of ground features which are too long and obscure ground detail. The OS do not usually hire aircraft during November to February because of this. On average there are only 16 days a year in the UK when photographs from above 10,000ft can be taken. The following table shows the hours flown on OS work from 1980 to 1987 and the number of aircraft used. 44

45. Photogrammetry 1 آ. رحمانی زاده Weather 45 YearHoursMain aircraftSupplementary aircraft 198026212 198122211 198233310 198327410 198427410 198530411 198628711 198720610

46. Photogrammetry 1 آ. رحمانی زاده Weather The main aeroplane operates for the whole season. The supplementary aircraft are used when the workload increases during the summer. As can be seen there are considerable variations in the number of days when aerial photography is possible. Aspects of the weather which affect visibility are – Haze Dust clouds storms, etc. 46

47. Photogrammetry 1 آ. رحمانی زاده 47 مراحل کلي کار در يک پروژه فتوگرامتري  برنامه ریزی  پرواز و عکسبرداری  عکاسی  تهیه اندکس  نقاط کنترل زمینی  مثلث بندی  تبدیل  تهیه نقشه  کارتوگرافی  چاپ

48. Photogrammetry 1 آ. رحمانی زاده 48 خلاصه این فصل  محدودة پوشش زميني عكس  عوامل كاهش پوشش طولي و عرضي  محاسبه تعداد عکسها و باندها  مراحل انجام عملیات فتوگرامتری

49. Photogrammetry 1 آ. رحمانی زاده 49 منابع  درسی  این  فصل  مبانی فتوگرامتری : بخش اول  مبانی فتوگرامتری : بخش دهم 10-9  An introduction to Air Survey Photography  Keith Atkinson (From lecture on 8/11/93 Keith Atkinson)  INTRODUCTION TO PHOTOGRAMMETRY  Robert Burtch (Center for Photogrammetric Training) Ferris State University

50. Photogrammetry 1 آ. رحمانی زاده پايان 50