فصل 8 : برجسته بيني و پارالاكس 65 Slide

برجسته بيني

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

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

Structure of human eye

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

MACULA LUTEAلکه زرد

Convergence

Perceiving object depth in human eyes

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

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

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

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

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

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

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

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

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

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

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)

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

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

VERTICAL EXAGGERATION (cont.)

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

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

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

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

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

VERTICAL EXAGGERATION (cont.)

VERTICAL EXAGGERATION (cont.) From the figure From which

VERTICAL EXAGGERATION (Example) Example: What is the approximate vertical exaggeration for a vertical photo taken with a 152.4-mm focal length camera having a 23-cm square format if the photos were taken with 60% endlap?

VERTICAL EXAGGERATION (Solution) Assuming be/h is 0.15

پارالاکس

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

STEREOSCOPIC PARALLAX

تعريف پارالاکس

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

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

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

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

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

الف) اندازه گيری پارالاکس بوسیله خط کش معمولی حالت اول

الف) اندازه گيری پارالاکس بوسیله خط کش معمولی حالت دوم

ب) اندازه گيری پارالاکس بوسیله پارالاکسبار

ب) اندازه گيری پارالاکس بوسیله پارالاکسبار (ادامه)

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

معادلات پارالاکس و کاربرد آن در فتوگرامتري

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

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'

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

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

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

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

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

ELEVATION BY PARALLAX DIFFERENCES (Cont.)

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

ELEVATION BY PARALLAX DIFFERENCES (Cont.) Alternative development

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

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

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

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

رابطه اختلاف پارالاکس با اختلاف ارتفاع

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

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

پایان فصل 8