1. فصل 8 : برجسته بيني و پارالاكس
65 Slide

2. برجسته بيني

3. DEPTH PERCEPTION
Binocular vision – capable of viewing with both eyes simultaneously
Stereoscopic viewing – perception of depth when viewing through binocular vision
Monocular vision – viewing with only one eye
Monoscopic viewing – judging depth with one eye

4. DEPTH PERCEPTION (cont.)
Distances perceived monoscipically by
Relative sizes of objects
Hidden objects
Shadows
Differencing in focusing

5. Structure of human eye

6. HUMAN EYE Pupil – circular opening where light passes
Protected by cornea
Light passes through lens and brought to focus at Central fovea
Iris – diaphragm
Optic nerve sends sense of vision to brain

7. MACULA LUTEAلکه زرد

8. Convergence

9. Perceiving object depth in human eyes

10. STEREOSCOPIC DEPTH PERCEPTION
When eyes fix on point, optical axes converge on that point, intersection at an angle called parallactic angle (φ)
Nearer object, greater parallactic angle
be – eye base About 2.6” (63-69 mm)
Depth between objects A and B is DB – DA

11. VIEWING PHOTOS STEREOSCOPICALLY
As A moves to A’, image marks (a’1 and a’2) on transparent medium move closer together
Parallactic angle increases and object perceived nearer
At A”, marks (a”1 and a”2) move apart
Parallactic angle decreases and object perceived farther away

12. VIEWING PHOTOS STEREOSCOPICALLY (cont.)
2 exposures made at L1 and L2
Building on both photos
B is air base – distance between exposures
H’ is flying height above ground
Top and bottom imaged on left photo at a1 and b1 and on right photo at a2 and b2

13. VIEWING PHOTOS STEREOSCOPICALLY (cont.)
Placing photos laid on table so left eye sees left image and right eye the right image
Stereoscopic model (called stereomodel) appears below table top
Brain judges height of building from differences in parallactic angle

14. تطابق و تقارب فاصله تطابق : فاصله شیء تا چشم
تقارب : تلاقی اشعه های دیدگانی
فاصله تقارب : محل تلاقی تا چشم

15. روشهاي برجسته بيني الف ) برجسته بينی با زاويه ديد متقاطع
ب) برجسته بينی با زاويه ديد متقارب
ج) برجسته بينی با زاويه ديد موازی

16. الف ) برجسته بينی با زاويه ديد متقاطع
فاصله تقارب
فاصله تطابق

17. ب ) برجسته بينی با زاويه ديد متقارب
فاصله تقارب
فاصله تطابق

18. ج ) برجسته بينی با زاويه ديد موازی
فاصله تقارب
فاصله تطابق

19. آشنايي با ابزارهاي مورد نياز براي برجسته بيني
الف) استرسکوپ جيبی
ب) استرسکوپ آينه ای
ج) سيستم مشاهده دستگاه های تـبديل

20. USE OF STEREOSCOPES
Accurate & comfortable stereoscopic viewing requires eye base, line between centers of stereoscope lenses, and flight line be parallel
Conjugate principal point (corresponding principal point)

21. Y-PARALLAX
Slight amounts causes eye strain & excessive amounts prevent stereoscopic viewing
Causes of y-parallax
Photos improperly oriented
Unequal flying height between photos
Tilt in photography

22. اغراق ارتفاعي در برجسته بيني
VERTICAL EXAGGERATION
Apparent scale disparity between horizontal and vertical scales
Primary cause: lack of equivalence between photographic base-height ratio, B/H’, and stereoviewing baseheight ratio, be/h

23. VERTICAL EXAGGERATION (cont.)

24. VERTICAL EXAGGERATION (cont.)
From aerial geometry:
From stereoscopic geometry:
Subtracting:

25. VERTICAL EXAGGERATION (cont.)
From similar triangles:
Subtracting yields:

26. VERTICAL EXAGGERATION (cont.)
Equating the 2 equations for xa – xc
But Z and z are considerably smaller than H’ and h, thus

27. VERTICAL EXAGGERATION (cont.)
From similar triangles in 2 diagrams
From which

28. VERTICAL EXAGGERATION (cont.)
Substitute into equation for z/Z
If Bh/(H’be) is 1, there is no vertical exaggeration. Thus, magnitude of vertical exaggeration, V, is given by

29. VERTICAL EXAGGERATION (cont.)

30. VERTICAL EXAGGERATION (cont.)
From the figure
From which

31. VERTICAL EXAGGERATION (Example)
Example: What is the approximate vertical exaggeration for a vertical photo taken with a mm focal length camera having a 23-cm square format if the photos were taken with 60% endlap?

32. VERTICAL EXAGGERATION (Solution)
Assuming be/h is 0.15

33. پارالاکس

34. PARALLAX
Apparent shift in the position of an object, with respect to a frame of reference, caused by a shift in the position of observation
Change in position of an image from one photo to the next is caused by aircraft’s motion
Called stereoscopic parallax, x parallax, or simply parallax
Two important aspects of stereoscopic parallax
Parallax of any point is directly related to the elevation of the point
Parallax is greater for high points than for low points

35. STEREOSCOPIC PARALLAX

36. تعريف پارالاکس

37. STEREOSCOPIC PARALLAX (cont.)
Parallax measured in flight-line axis system

38. MONOSCOPIC PARALLAX MEASUREMENT
Mark conjugate principal points
Align flight line axis
Parallax:

39. PRINCIPLE OF FLOATING MARK
When viewing in stereo, 2 small identical marks etched on clear glass
– Called half marks
Half marks shifted until they fuse into single mark
If marks moved closer together, they appear to rise
If moved apart, marks appear to fall
Spacing of half marks, hence their parallax, varied so floating marks appears to rest exactly on terrain

40. PARALLAX OF PRINCIPAL POINT
Parallax of left ground principal point is photo base b’ measured on right photo, and the parallax of right ground principal point is photo base b measured on left photo
For moderate relief, b ≈ b’
Photo base is average of two values

41. روشهای اندازه گيری پارالاکس
الف) روش خط کش معمولی
ب) روش پارالاکسبار

42. الف) اندازه گيری پارالاکس بوسیله خط کش معمولی
حالت اول

43. الف) اندازه گيری پارالاکس بوسیله خط کش معمولی
حالت دوم

44. ب) اندازه گيری پارالاکس بوسیله پارالاکسبار

45. ب) اندازه گيری پارالاکس بوسیله پارالاکسبار (ادامه)

46. ب) اندازه گيری پارالاکس بوسیله پارالاکسبار (ادامه)
محاسبه ثابت پارالاکسبار

47. معادلات پارالاکس و کاربرد آن در فتوگرامتري

48. DEVELOPMENT OF PARALLAX EQUATIONS
Triangles LOW and Low, write scale:
From triangles Lwp and LWP, write scale:

49. DEVELOPMENT OF PARALLAX EQUATIONS (cont.)
Using triangles L’O’W, L’o’w’, L’w’p’, L’WP
From last two relationships:
Yielding:
y = y'

50. DEVELOPMENT OF PARALLAX EQUATIONS (cont.)
In triangles LWL’ & Lww’
LL’ is parallel to ww’
LW is parallel to Lw
L’W is parallel to Lw’
The two triangles are similar triangles
Corresponding altitudes are (H – h) and f

51. DEVELOPMENT OF PARALLAX EQUATIONS (cont.)
From similar triangles
Since
ww'= x − x'= p
then

52. DEVELOPMENT OF PARALLAX EQUATIONS (cont.)
The parallax equation are:

53. PARALLAX EQUATIONS Valid for
Truly vertical photographs only
Photos taken from same flying height
Coordinates (x, y, x’, y’) related to flight line axis system
Ground coordinates not related to true ground coordinates but to the coordinate system of the stereopair

54. ELEVATION BY PARALLAX DIFFERENCES
Recall parallax formula:
Rearrange for points a and c

55. ELEVATION BY PARALLAX DIFFERENCES (Cont.)

56. ELEVATION BY PARALLAX DIFFERENCES (Cont.)
Substituting parallax formula for flying height above the terrain
From which

57. ELEVATION BY PARALLAX DIFFERENCES (Cont.)
Alternative development

58. ELEVATION BY PARALLAX DIFFERENCES (Cont.)
Since ground principal points lie on same datum
Since O1, O2 and C lie at same elevation, their parallaxes are the same

59. ELEVATION BY PARALLAX DIFFERENCES (Cont.)
From figure
From which

60. ELEVATION BY PARALLAX DIFFERENCES (Cont.)
Substitute in elevation difference formula and recognizing that

61. معادلات پارالاکس و کاربرد آن در فتوگرامتري
N = عدد مقياس عکس

62. رابطه اختلاف پارالاکس با اختلاف ارتفاع

63. خلاصه این فصل تعريف برجسته بيني اصول و روشهاي برجسته بيني
آشنايي با ابزارهاي مورد نياز براي برجسته بيني
اغراق ارتفاعي در برجسته بيني
تعريف پارالاکس
انواع پارالاکس و تفاوت آنها
روشهای اندازه گيری پارالاکس
معادلات پارالاکس و کاربرد آن در فتوگرامتري

64. منابع درسی این فصل مبانی فتوگرامتری : بخشهاي اول، پنجم و ششم
INTRODUCTION TO PHOTOGRAMMETRY
Robert Burtch (Center for Photogrammetric Training) Ferris State University
Photogrammetry : Chapter 5

65. پایان فصل 8