Photogrammetry 2003

8/13/2019 Photogrammetry 2003

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PHOTOGRAMMETRY an introduction


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Photogrammetry is the technique of

measuring objects !" or #"$ from

%hotogra%hs&

'ts most im%ortant feature is thefact( that the objects are measured

without being touched&


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PHOTOGRAMMETRY

objects are measured )'THO*T TO*+H',G&

't is a REMOTE-E,-',Gtechnique& 't is a c.ose range method of measuring objects&

't is a #/dimensiona. coordinate measuring techniquethat uses PHOTORAPH-as the fundamenta. medium

for measurement&


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Brief History of Photogrammetry 1851: French officer Aime Laussedat develops the first

photogrammetrical devices and methods. He is seen asthe initiator of photogrammetry.

1858: The German architect A. eyden!auer developsphotogrammetrical techni"ues for the documentation

of !uildings and installs the first photogrammetricinstitute in 1885 #$oyal %russian %hotogrammetric&nstitute'.

1885: The ancient ruins of %ersepolis (ere the firstarchaeological o!)ect recorded photogrammetrically.

188*: The first German manual of photogrammetry(as pu!lished !y +. ,oppe.


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History cont 1*11: The Austrian Th. -cheimpflug finds a (ay to create rectified

photographs. He is considered as the initiator of aerialphotogrammetry since he (as the first succeeding to apply thephotogrammetrical principles to aerial photographs

1*1/: The first congress of the &-% #&nternational -ociety for%hotogrammetry' (as held in 0ienna.

1*8ies: 2ue to improvements in computer hard(are and soft(aredigital photogrammetry is gaining more and more importance.

1**3: 8/ years after its first conference the &-%$- comes !ac4 to0ienna the to(n (here it (as founded.


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00PR',+'P1E00

The main %rinci%.e is2TR'A,G*1AT'O,3&

Eyes use the %rinci%.e ofTR'A,G*1AT'O,togauge

distance de%th %erce%tion$&

TR'AG*1AT'O,is a.so the %rinci%.e used by

theodo.ites for coordinate measurement.


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TR'A,G*1AT'O,

By taing !hotogra!hs from at "east twodifferent "ocations# so$ca""ed %"ines of sight%

can be de&e"o!ed from each camera to !ointson the ob'ect( These "ines of sight )sometimes

ca""ed rays owing to their o!tica" nature* are

mathematica""y intersected to !roduce the +$dimensiona" coordinates of the !oints of

interest(


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Photogra%hythe first %art


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Photogra!hy $ The ,irst Part of

Photogrammetry Ta4ing photographs is of course essential for ma4ing

photogrammetric measurement. To o!tain the high

accuracy relia!ility and automation the system iscapa!le of photographs must !e of the highest "uality

The three main considerations for good photography are:

1. Field of View

2. Focusing

3. Exposure


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Metro"ogy $ The -econd Part of

Photogrammetry


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Photogrammetry can be di4ided

into51.Depending on the lenses-setting:

A&&6ar range %hotogrammetry 7ith camera distance setting to

indefinite$ 8& +.ose range %hotogrammetry 7ith camera distance settings

to finite 4a.ues$&

2.Another grouping can be:

A& Ariea. %hotogrammetry 7hich is most.y far range

%hotogrammetry$

8& Terrestria. Photogrammetry most.y c.ose range

%hotogrammetry$&


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-hort descri!tions of

!hotogrammetric

techni.ues


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Photogra!hing /e&ices

1.A %hotogra%hic image is a 9centra. %ers%ecti4e2& This im%.ies( that e4ery.ight ray( 7hich reached the fi.m surface during e:%osure( %assed throughthe camera .ens 7hich is mathematica..y considered as a sing.e %oint( theso ca..ed 9%ers%ecti4e center2$&

!& 'n order to ta;e measurements of objects from %hotogra%hs( the ray bund.emust be reconstructed&

#& The foca. .ength is ca..ed 9%rinci%a. distance2( 7hich is the distance of the%rojection center from the image %.ane


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Metric cameras They ha&e stab"e and !recise"y nown

interna" geometries and &ery "ow "ensdistortions(

The !rinci!a" distance is constant#which means# that the "ens cannot be

shar!ened when taing !hotogra!hs(

The image coordinate system isdefined by )most"y* four fiducia"mars# which are mounted on theframe of the camera(

Aeria" metric cameras are bui"t intoaero !"anes most.y .oo;ing straightdo7n7ards&


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Stereometric camera

The o4er.a%%ing area of these t7o %hotogra%hs 7hich are ca..ed a9stereo%air2$ can be seen in #"( simu.ating man


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Amateur cameras

The %hotogrammetrist s%ea;s of an 9amateur camera2( 7hen the interna. geometry

is not stab.e and un;no7n( as is the case 7ith any 9norma.2 commercia..y a4ai.ab.e

camera&

Photogra%hing a test fie.d 7ith many contro. %oints and at a re%eatab.y fi:eddistance setting for e:am%.e at infinity$( a 9ca.ibration2 of the camera can be

ca.cu.ated&

They can on.y be used for %ur%oses( 7here no high accuracy is demanded&

The %recision 7i.. ne4er reach that of metric cameras&


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Photogrammetric

Techni.ues


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Mapping from a single photograph

On.y usefu. for %.ane !"$ objects&

Ob.ique.y %hotogra%hed %.ane objects sho7 %ers%ecti4edeformations 7hich ha4e to be rectified&

To get good resu.ts e4en 7ith the sim%.e techniques( the

object shou.d be %.ane as for e:am%.e a 7a..$( and since

on.y a sing.e %hotogra%h is used( the ma%%ings can on.y be

done in !" &


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Mapping from a singlephotograph

-ome +ommon

Techniques5


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00(Pa!er stri! method(Pa!er stri! method11(O!tica" rectification(O!tica" rectification

++(2umerica" rectification(2umerica" rectification33(Mono!"otting(Mono!"otting

44(/igita" rectification(/igita" rectification


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0(Pa!er stri! method0(Pa!er stri! method

This is the chea!est method# since on"y a ru"er# a !iece of!a!er with a straight edge and a !enci" are re.uired(

,our !oints must be identified in the !icture and in a ma! (

The !a!er stri! is !"aced on the image and the intersections

with the "ines are mared

The stri! is then !"aced on the ma! and ad'usted such that

the mars coincide again with the "ines.

After that# a "ine can be drawn on the ma! to the marof the re.uired ob'ect !oint( The who"e !rocess is

re!eated from another !oint# gi&ing the ob'ect$!oint on

the ma! as intersection of the two ob'ect$"ines(


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1( O!tica" rectification1( O!tica" rectification

5s done using !hotogra!hic en"argeners.

At "east four contro" !oints are re.uired# not three

on one "ine(

The contro" !oint !"ot is rotated and dis!"aced unti"

two !oints match the corres!onding ob'ect !oints

from the !ro'ected image(

After that# the tab"e has to be ti"ted by two rotations#unti" the !ro'ected negati&e fits to a"" contro" !oints(

Then an e6!osure is made and de&e"o!ed.


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+(Mono!"otting+(Mono!"otting The coordinates are here transformed into a +/

coordinate system(

,irst# the orientation e"ements# that are the coordinates

of the !ro'ection center and the three ang"es defining the

&iew of the !hotogra!h# are ca"cu"ated by s!atia"

resection(

Then# using the ca"ibration data of the camera# any ray#

that came from the archaeo"ogica" feature through the"ense onto the !hotogra!h can be reconstructed and

intersected with the digita" terrain mode"&


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Stereophotogrammetry

-tereo%airs are the basic requirement( here. These can be %roduced using stereometric cameras& 'f

on.y a sing.e camera is a4ai.ab.e( t7o %hotogra%hs canbe made from different %ositions( trying to match the

conditions of the 9norma. case2& )hi.e ta;ing the %hotogra%hs( the aero%.ane f.ies o4er

certain area in a meandric 7ay( so that the 7ho.e area ico4ered by o4er.a%%ing %hotogra%hs&

The o4er.a%%ing %art of each stereo%air can be 4ie7edin #" and consequent.y ma%%ed in #" using one offo..o7ing techniques5


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Ana.ogue Method T7o %rojectors( 7hich ha4e the same geometric

%ro%erties as the used camera %roject the negati4es ofthe stereo%air&

Their %ositions then e:act.y rotated into the same

re.ationshi% to7ards each other as at the moment ofe:%osure (After this ste%( the %rojected bund.e of .ightrays from both %hotogra%hs intersect 7ith each otherforming a three dimensiona. o%tica.$ 9mode.&

At .ast( the sca.e of this mode. has to be re.ated to itstrue dimensions and the rotations and shifts in re.ationto the ma%%ing 7or.d$ coordinate system are

determined&


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Ana.ytica. Method

A com%uter manages the re.ationshi% bet7een image/ and rea./7or.d coordinates&

After restoration of the @inner orientation@( 7here the com%uter

may no7 a.so correct for the distortion of the fi.m( both %ictures

are re.ati4e.y oriented& Then( the abso.ute orientation is %erformed( 7here the #" mode.

is transferred to the rea./ 7or.d coordinate system& Therefore( at

.east three contro. %oints are required.

The ana.ytica. %.otter uses the com%uter to ca.cu.ate the rea./7or.dcoordinates( 7hich can be stored as an A-+'' fi.e or transferred on/

.ine into +A"/%rograms& 'n that 7ay( #" dra7ings are created( 7hich

can be stored digita..y( combined 7ith other data and %.otted .ater at

any sca.e&


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Ma!!ing from se&era"

!hotogra!hs This ;ind of restitution( 7hich can be done in #"( has

on.y become %ossib.e by ana.ytica. and digita.

%hotogrammetry&

Here( most.y more than t7o %hotogra%hs are used& #"

objects are %hotogra%hed from se4era. %ositions&

The %hotogra%hs can be ta;en 7ith different camerase4en 9amateur2 cameras$ and at different times if the

object does not mo4e$&


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Technique

On.y ana.ytica. or digita. techniques can be used& "uring a.. methods( first a bund.e adjustment has to be

ca.cu.ated&

*sing contro. %oints and triangu.ation %oints thegeometry of the 7ho.e b.oc; of %hotogra%hs is

reconstructed 7ith high %recision&

Then the image coordinates of any desired object/%oint

measured in at .east t7o %hotogra%hs can be intersected&

The resu.t are the coordinates of the required %oints&

'n that 7ay( the 7ho.e #" object is digita..y

reconstructed&


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+onc.usion

Photogrammetry can a.so be thought of as thesciences of geometry( mathematics and %hysicsthat use the image of a #" scene on a !" %iece

of %a%er to reconstruct a re.iab.e and accuratemode. of the origina. #" scene()ith this in mindit is easier to understand the current e:%andeddefinition( 7hich( inc.udes the science of e.ectronics

by using 4ideo and other synthetic means ofre%roducing !" images of #" scenes& And( theseimages are a.so used to reconstruct re.iab.e andaccurate mode.s of the ca%tured #" scenes&


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Terms.

1. Photogrammetry

2. ectified photographs

3. Triangulation

!. "auge distance

#. Photogrammetric measurement

$. Field of %iew

&. Focusing

'. Exposure

(. )tereometric camera

1*. ay

11. +ap


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