Technical assistance from Republic of Latvia offered to Iraq in the field of architectural sites documentation by photogrammetrical methods Mr. G.Goldbergs Mr. M.Kalinka  Riga Technical University

Aim of training programme To show and to learn in practice the combination a modern total station and a non-metric digital camera to derive digital orthoimages of architectural objects - Digital orthoimages provide most of the geometric and radiometric information required for documentation of facades

The main steps of creation of orthoimages camera calibration make the geodetical network to measure the controlmarks on the object take the photography image triangulation digital surface model (DSM) creation and editing orthophoto creation post processing of the data (vectorizing)

DSM Evaluation of all the geometric distortions Two Dimensional Adjustment Interior Orientation Distortion Original Image Fiducial Marks Control Points Camera Calibration Results Phototriangulation rectification of images DSM Original Image Projection Orthophoto Flow Chart for Digital Orthophoto

The technical equipment and software digital camera with tripod total station with tripod reflecting sheets and reflecting prism geodetical network adjusting software camera calibration software or camera calibration test field close range photogrammetrical software

Camera calibration - 2D dimensions calibration grid particular software PhotoModeler Pro 5.0 (Canada) - 4Mpix non-metric digital camera Olympus C-765Z.

Instability of the iterior orientations parameters using PhotoModeler Pro 5.0 RMS f(c)= 0,026 mm RMS xp = 0,017 RMS yp = 0,009 mm ~ 11 pixels ~7 pixels ~4 pixels Shorter focal length of digital camera – larger instability of interior parameters Necessary to perform camera calibration before each project (photo session)

Mosque of Ahmed Ibn Tulun, Cairo, Egypt

Geodetic network and control marks field The geodetic network is very important to measure the control marks of the objects and connect all measurements together for 3D modeling. The final result of image triangulation depends on the precision of the geodetic network and measuring methods of the control marks. The special reflecting sheets on the white background are the best high precision technical material for putting the control marks. To measure the control marks use the electronically tacheometry with minimum 5“ angle and 2 mm distance measuring precisions. For training, we used the special SOKKIA reflector sheets and electronic tachometer SET 310.

Geodetic network and control marks field

Photography. The normal case geometry B - photography base m – image scale D – distance between camera and object c – focal length l – image size

Phototriangulation 6 signalized control points in four stereo models.

Phototriangulation

Digital Surface model (DSM) In architectural photogrammetry the relation between object height differences and distance between camera and object is much bigger than in aerial photogrammetry. The errors in the digital surface models have a larger influence on the accuracy of the produced orthoimages, than in aerial photogrammetry. - The DSM was created using vectors and breaklines vectorized manually:

Digital Surface model (DSM) - elevation matrix for part of the wall

Orthophoto creation (mosaic)

Orthophoto 1 pixel = 5 mm

Documentation of cultural heritage There are many various kinds of the documentation: - orthophoto of the parts of objects - 3D model with pictures - 2D model of the object geometry in CAD programs Fusion of the results of geodetic survey, 3D laser scanner, photogrammetric and post-processing data The joint CAD model may be used to derive all required plans, models, or visualizations.

More results north_centre_part west_centre_part

Conclusions Amateur digital non-metric cameras under certain limited accuracy requirements can be used for wide low-accuracy photogrammetric purposes eg. buildings documentation etc. The amateur digital cameras with number of pixels equal or more than 5 Mpix are well suited for photogrammetric purposes. To minimize Y coordinates errors, the image overlapping should be > 65% The orthoimages and its digital surface models (DSM) are fastest way to provide most of the geometric and radiometric information required for the documentation of architectural /archaeological sites. Defining and signalizing of control points and knowing coordinates of image projective centers could improve the accuracy of image triangulation.

Mr. J.Kletnieks, Mr. B.Deslandes, UNESCO, Literature Birute Ruzgiene, Vilnius Technical University. Performance evaluation of non-metric digital camera for photogrammetric application. Geodesy and cartography,2005, Vol XXXI,No1 Albert Weidemann, Technical Univercity of Berlin, Digital orthoimages in architectural photogrammetry using digital surface models. Special Thanks To: Mr. J.Kletnieks, Mr. B.Deslandes, UNESCO, Government of the Republic of Latvia, State Land service of Latvia, Riga Technical Univercity

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