Introduction To Geomatics

King AbdulAziz UniversityFaculty of Environmental DesignGeomatics DepartmentIntroduction to GeomaticsGEOM 101Week 8Introduction to Photogrammetry ﻗﺴﻢ اﻟﺠﯿﻮﻣﺎﺗﻜﺲ Ahmad Baik, Ph.D.Email: abaik@kau.edu.sa

Lecture 5: Introduction toPhotogrammetrySummaryI.What is PhotogrammetryII.Principles of Human VisionIII.Branches of PhotogrammetryIV.Principles of Photogrammetry ﻗﺴﻢ اﻟﺠﯿﻮﻣﺎﺗﻜﺲ

Lecture 5: Introduction toPhotogrammetryWhat is PhotogrammetryEtymologyEtymologically, the term photogrammetry is composed of threeGreek roots : ‘Photo’, ‘Gram’ and ‘Metry’.* Photos: which means ‘Light’.* Graphein : which means ‘Write’ (or ‘Draw’)* Metron : which means ‘Measure’Hence, we can deduce the etymological meaning as ‘the science ofmeasuring from photographs ’ ﻗﺴﻢ اﻟﺠﯿﻮﻣﺎﺗﻜﺲ

Lecture 5: Introduction toPhotogrammetryWhat is PhotogrammetryASPRS DefinitionThe American Society of Photogrammetry and Remote Sensing(ASPRS) defines photogrammetry as ‘the science, art andtechniques of obtaining reliable information about physicalobjects and the environment. This is done through a process ofrecording, measuring, and interpreting aerial and terrestrialphotographs ’. ﻗﺴﻢ اﻟﺠﯿﻮﻣﺎﺗﻜﺲ

Lecture 5: Introduction toPhotogrammetryWhat is PhotogrammetryPhotogrammetry WorkflowA standard workflow of Photogrammetry contains three mainphases which are: 1) Data Acquisition, 2) PhotogrammetricProcedures and 3) Photogrammetric Products.Data aphic MapsAeroTriangulationDigital ElevationModelFilm CameraDigital Camera ﻗﺴﻢ اﻟﺠﯿﻮﻣﺎﺗﻜﺲ

Lecture 5: Introduction toPhotogrammetryPrinciples of Human VisionThe principles of Photogrammetry come from the understandingof how Human eyes work. In fact, the lens of the eyes act like aconvex lens that produces an image of the object on the retina.The produced image, which has an inversed orientation, is thentransmitted to the brain through the optic nerve in order to beinterpreted.EyeRetinaObjectEye’s Lens ﻗﺴﻢ اﻟﺠﯿﻮﻣﺎﺗﻜﺲ

Lecture 5: Introduction toPhotogrammetryPrinciples of Human VisionMonoscopyThe monoscopy is the process of vision that involves only a singleeye. Although the image formed on the retina contains a hugeamount of information, the monoscopy provides only a twodimensional representation of the scene (the perception doesn’tcontain any information about the depth of the scene).Left Eye ﻗﺴﻢ اﻟﺠﯿﻮﻣﺎﺗﻜﺲ

Lecture 5: Introduction toPhotogrammetryPrinciples of Human VisionStereoscopyThe Stereoscopy is the process of vision that involves the two eyesat the same time. The Stereoscopy allows perceiving the thirddimension of the scene, through the brain interpretation of the twoimages that are formed on the left and right retinas.Left Eye ﻗﺴﻢ اﻟﺠﯿﻮﻣﺎﺗﻜﺲ Right Eye

Lecture 5: Introduction toPhotogrammetryPrinciples of Human VisionParallactic AngleThe Human brain does not make any ‘graphical’ report of therays that come from the scene. It analyses the angle between thetwo light beams (that come from one object) which are perceived byeach eye. This angle is called ‘Parallactic Angle’.Left EyeA point which is closer to thehuman eyes has a largeparallactic angle, and pointwhich is farther has a smallerparallactic angle. ﻗﺴﻢ اﻟﺠﯿﻮﻣﺎﺗﻜﺲ Right Eye

Lecture 5: Introduction toPhotogrammetryBranches of PhotogrammetryThere are many methods used in photogrammetry in order toextract information from photos. However, Photogrammetry may bedivided into two main groups: 1) Aerial Photogrammetry and 2)Close range (or Terrestrial) Photogrammetry.In addition, Aerial Photogrammetry may also be classified intothree categories:1- Analog Photogrammetry,2- Analytical Photogrammetry,3- Digital Photogrammetry, ﻗﺴﻢ اﻟﺠﯿﻮﻣﺎﺗﻜﺲ

Lecture 5: Introduction toPhotogrammetryBranches of PhotogrammetryThe development ndinnovation related t0the used technologies(photography,airplanes, computersand electronics). ﻗﺴﻢ اﻟﺠﯿﻮﻣﺎﺗﻜﺲ

Lecture 5: Introduction toPhotogrammetryBranches of PhotogrammetryAnalog PhotogrammetryAnalog Photogrammetry is the branch of Photogrammetry thatincludes all methods and techniques to extract information fromanalog photos based on mechanical and optical methods or theircombination.The Principle of Analog Photogrammetry is to produce in thelaboratory, and on a smaller scale, the configuration of thecamera when taking pictures in two positions. Thisconfiguration is reconstructed by using optical and mechanicalinstruments. ﻗﺴﻢ اﻟﺠﯿﻮﻣﺎﺗﻜﺲ

Lecture 5: Introduction toPhotogrammetryBranches of PhotogrammetryAnalog PhotogrammetryExample of an analog instrument for Photogrammetry ﻗﺴﻢ اﻟﺠﯿﻮﻣﺎﺗﻜﺲ

Lecture 5: Introduction toPhotogrammetryBranches of PhotogrammetryAnalytical PhotogrammetryAnalytical Photogrammetry is also based on the reconstruction ofcamera’s positions during the flight mission. However, thereconstruction is not performed mechanically.Although the used photos are analog, the principle of AnalyticalPhotogrammetry is to reconstruct mathematically theconfiguration of cameras during the flight using computers. ﻗﺴﻢ اﻟﺠﯿﻮﻣﺎﺗﻜﺲ

Lecture 5: Introduction toPhotogrammetryBranches of PhotogrammetryAnalytical PhotogrammetryExample of an analytical instrument for Photogrammetry ﻗﺴﻢ اﻟﺠﯿﻮﻣﺎﺗﻜﺲ

Lecture 5: Introduction toPhotogrammetryBranches of PhotogrammetryDigital PhotogrammetryDigital Photogrammetry uses the same mathematical alPhotogrammetry (in contrast to Analytical Photogrammetry) usesDigital Photos.Digital Photos may come eitherfrom scanning existing AnalogPhotos, or directly acquired fromDigital camera (see picture below). ﻗﺴﻢ اﻟﺠﯿﻮﻣﺎﺗﻜﺲ

Lecture 5: Introduction toPhotogrammetryBranches of PhotogrammetryDigital PhotogrammetryExample of an Digitalinstrument for Photogrammetry ﻗﺴﻢ اﻟﺠﯿﻮﻣﺎﺗﻜﺲ Leica Photogrammetric HighResolution Scanner

Lecture 5: Introduction toPhotogrammetryBranches of PhotogrammetryClose –range (Terrestrial)PhotogrammetryClose-range (or Terrestrial)Photogrammetry uses the sametheoretical basis as AerialPhotogrammetry. In the case,the photos are taken from a veryclose distance from the objectto be photographed. ﻗﺴﻢ اﻟﺠﯿﻮﻣﺎﺗﻜﺲ

Lecture 5: Introduction toPhotogrammetryPrinciples of PhotogrammetryCharacteristics aerial photographyMarginal data of aerial photographyFiducial marks: small registrationmarks exposed on the edges of aphotograph. The distances betweenfiducialmarksarepreciselymeasured when a camera iscalibrated.Roll and Photo Numbers: eachaerial photo is assigned a uniqueindex number according to thephoto's roll and frame.Geographic location, time anddate, etc. ﻗﺴﻢ اﻟﺠﯿﻮﻣﺎﺗﻜﺲ

Lecture 5: Introduction toPhotogrammetryPrinciples of PhotogrammetryCharacteristics aerial photographyFocal and ScaleFocal length: the distance from themiddle of the camera lens to thefocal plane (i.e. the film). Thefocallengthispreciselymeasured when the camera iscalibrated.Scale: the ratio of the distancebetween two points on a photo tothe actual distance between thesame two points on the ground. ﻗﺴﻢ اﻟﺠﯿﻮﻣﺎﺗﻜﺲ

Lecture 5: Introduction toPhotogrammetryPrinciples of PhotogrammetryCharacteristics aerial photographyDistortion on aerial photographyThe projection of a photography is a perspective (or central)projection, because all the rays should pass through a point calledthe center of perspective. This type of projection causes animportant distortions especially for taller object on the scene. ﻗﺴﻢ اﻟﺠﯿﻮﻣﺎﺗﻜﺲ

Lecture 5: Introduction toPhotogrammetryPrinciples of PhotogrammetryStereoscopic coverageThe concept of Stereoscopy inphotogrammetry is one of themost important notions. It usesthe same principle of humanvision in order to extract theelevation of an object in a scene. Toretrieve the elevation from a scene ithastobenecessaryphotographed from to differentperspectives (Overlap region). ﻗﺴﻢ اﻟﺠﯿﻮﻣﺎﺗﻜﺲ Overlap Region

Lecture 5: Introduction toPhotogrammetryPrinciples of PhotogrammetryStereoscopic coverageOverlap: is the amount by whichone photograph includes thearea covered by anotherphotograph, and is expressed as apercentage. The photo survey isdesigned to acquire 60 per centforwardoverlap(betweenphotos along the same flightline) and 30 per cent lateraloverlap (between photos onadjacent flight lines). ﻗﺴﻢ اﻟﺠﯿﻮﻣﺎﺗﻜﺲ

Lecture 5: Introduction toPhotogrammetryPrinciples of PhotogrammetryStereoscopic restitutionThe Stereoscopic restitution consists of reconstructing astereoscopic model (which will be seen by the operator) from twoimages that were taken from different angles. To do so, each eyehas to see only the corresponding image (left or right), and thehuman brain will automatically perceive the three-dimension.Left EyeLeft Image ﻗﺴﻢ اﻟﺠﯿﻮﻣﺎﺗﻜﺲ Right EyeRight Image

Lecture 5: Introduction toPhotogrammetryPrinciples of PhotogrammetryStereoscopic restitutionThere many methods used to display the corresponding image foreach eye. The most used methods are: 1) Optical Stereoscope, 2)Anaglyph (with complementary colors) and 3) Polarization(polarized filters).Example of Optical Stereoscope ﻗﺴﻢ اﻟﺠﯿﻮﻣﺎﺗﻜﺲ

Lecture 5: Introduction toPhotogrammetryPrinciples of PhotogrammetryStereoscopic restitutionExample of AnaglyphTo display the two images, we use aspecialglasswithtwocomplementary colors (cyan andRed for example). Hence, eacheye will see only one of the twoimages. ﻗﺴﻢ اﻟﺠﯿﻮﻣﺎﺗﻜﺲ

Lecture 5: Introduction toPhotogrammetryPrinciples of PhotogrammetryStereoscopic restitutionExample of PolarizationTo display the two images, we use aspecial glass with two differentpolarization (Horizontal andVertical for example). Hence,each eye will see only one of thetwo images. ﻗﺴﻢ اﻟﺠﯿﻮﻣﺎﺗﻜﺲ

Lecture 5: Introduction toPhotogrammetryPrinciples of PhotogrammetryStereoscopic restitutionIn order to construct a Stereo Model, it is necessary to reconfigurethe position of the two images as their initial positions duringthe flight mission.The process of Stereoscopic restitution consists of three mainphases:1- Interior orientation2- Relative orientation3- Absolute orientationSometimes, relative and absolute orientation may be combined inone step called Exterior orientation. ﻗﺴﻢ اﻟﺠﯿﻮﻣﺎﺗﻜﺲ

Lecture 5: Introduction toPhotogrammetryPrinciples of PhotogrammetryStereoscopic restitutionInterior OrientationThe aim of Interior orientation is to define a Photo coordinatesystem for each Photography. This is very important in order toreconstruct the Perspective Projection of each image. To do so, weuse the fiducial marks for each photography. ﻗﺴﻢ اﻟﺠﯿﻮﻣﺎﺗﻜﺲ

Lecture 5: Introduction toPhotogrammetryPrinciples of PhotogrammetryStereoscopic restitutionRelative OrientationThe aim of Relative orientation is to the relative position of twophotographs, or a relation to another. To do so, an image is fixedand we ‘drag and rotate’ the other until finding the relative positionas the flight mission. "Drag and rotate" means to move the imagearound the axis ω (Omega), φ (Phi) and K (Kappa),corresponding to X, Y and Z. ﻗﺴﻢ اﻟﺠﯿﻮﻣﺎﺗﻜﺲ