Paralaks,stereo photo,and relief displacement

8/18/2019 Paralaks,stereo photo,and relief displacement.

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Relief Displacement, Paralaks dan Stereo


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Para ax Fun amenta s

• Method

of

measuring

distance

called

parallax .• Example: – Hold pencil at arm’s length, and close each eye in turn.

– Each e e looks at encil from sli htl different direction.

– Brain determines

object’s

distance

from

slight

change

in

direction.

(parallax)

• For distant objects, small distance between eyes means parallax angle too small to see change in direction.

to

increase

perspective.


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Ima e Parallax

• Applications of photogrammetry use the principle of parallax to incorporate stereo pairs.

• Parallax is the apparent change in relative positions of stationary

• These displacements form the basis of three dimensional viewing

of overlapping

photos.

.

• Image centers of preceding and succeeding photographs called conjugate principal points.

• Line drawn through principal and conjugate principal points defines the flight axis.


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Parallax Displacements on Overlapping

er ca

o ograp s

• The parallax of any point such as +y

A in

terms

of

flight

line

coordinate system: a b a´ b´xa xa´+x +x´o o´ o o´

+y´

pa = xa – xa’

where´ ´

L L´

o

o´

– pa = para ax o po n

– xa = measured x coordinate of

ima e a on left hoto ra h x

a a

positive)

– xa’ = x coordinate of image a´ on A

B

r g t p otograp xa pos t ve


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Parallax

Stereo View


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• Typical aerial imaging geometry: 60% forward overlap (= 10% triple overlap) and

25% sidelap.

• T is gives u stereo coverage or t e w o e area.


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Stereo Images – Seeing in 3D

•

it is

possible

to

view

airphotos

stereoscopically,

i.e.,

three

dimensional

(3D) viewing.

• This is limited to area of overlap between the two images.

• Stereoscopic

viewing

is

based

on

binocular

vision. .

• Brain reconstructs two images recorded by our eyes into 3D view of the scene.

Same t ing

is

possi e

wit

airp oto

pair

provi e

t at

eac

p oto

is

viewed by each eye separately.


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Produk FotogrametriProses Pemotretan dengan Pesawat terbang:


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Vertical Aerial Photographs


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Pemotretan Udara

1 2 3 4 5 6

A strip of overlapping aerial photographs

Strip 1Sidelap

Strip 2

Strip 3

A block of overlapping strips


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Stereo

Photograph

Geometry

Flight

characteristics

•Overlapping photos are necessary to produce stereo effect. Photos taken along the

flight line

need

to

have

at

least

50%

overlap. Normally

60%

overlap

is

specified

for

a

flight mission. Overlap along flight line is also known as endlap.

•The area that is common between successive photos is called overlap. A stereo

model is created when successive photos are viewed with a stereoscope.

•Normally when an area is flown for stereo coverage, sidelap between flight lines is

necessary for complete coverage. 30% sidelap is normal for most flight plans.

Direction of flight


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Relief Displacement

• principal

point

will

lean

outward.

As t e stance rom t e

principal point increases,

the radial

displacement

increases.

• The cooling towers closer to

greater radial displacement.

(Rutgers)


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Displacement of Object Features

Cameras for aerial photography provide

" "

from directly

overhead.

Primary geometric distortion in

vertical aerial photographs due to

relief displacement

ec s rec y e ow cen er o

camera lens (i.e. at the nadir) will

have only their tops visible

All other

objects

will

appear

to

lean

away from the center of photo so (Relief Displacement)

a e r ops an s es are v s e


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Relief Displacement

•

perspective projection.

• Use this to determine the hei ht of ob ect:

h= d (H’)d (H’)

rr

h = height of object

‐

bottom of object.

= .

H’ = height

of

plane

above

ground

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Paralaks,stereo photo,and relief displacement