Photogrammetry in architecture, archaeology and urban conservation

boberg, anders; lagerqvist, bosse

Bibliographic data

Monograph

Persistent identifier:: 1030399344

Author:: Walton, William

Title:: Problems in illustration of the principles of plane coordinate geometry

Scope:: 1 Online-Ressource (VIII, 429 Seiten)

Year of publication:: 1851

Place of publication:: Cambridge [u.a.]

Publisher of the original:: Deighton [u.a.]

Identifier (digital):: 1030399344

Illustration:: Illustrationen

Signature of the source:: Mr.II 8825

Language:: English

Usage licence:: Public Domain Mark 1.0

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2018

Document type:: Monograph

Collection:: Mathematics

1991. G.1.S. A. on: ystems, Special astles’, 29(B5), 1. LOW COST DIGITAL ACQUISITION SYSTEMS FOR ARCHITECTURAL PHOTOGRAMMETRY P. Boccardo, A. Lingua, F. Rinaudo - Politecnico di Torino - ITALY KEY WORDS: Digital Photogrammetry, Acquisition Unit, Calibration, Low cost ABSTRACT The digital approach is becoming the new standard throughout the whole photogrammetric world. In particular, in architectural survey applications, it is now possible to find useful hardware and software products to obtain sufficient precision with low costs. As it is known, a digital photogrammetric system consists of an acquisition unit and a restitution unit. The acquisition unit is the hardware and software devoted to produce digital images where the theoretical central perspective co-ordinates of the object are directly linked to each pixel. The restitution unit is the hardware and software devoted to the production of rectifications, orthopho- tos and 3D-surveys of the object using the digital images produced by the acquisition unit. This paper describes the modern possible configurations of the acquisition units that are suitable for standard applications in archi- tectural photogrammetry. Both the direct acquisition unit, based on modern digital cameras (e.g. NIKON E2) and the hard copy scanning unit, based on DTP scanners, are described in detail and the practical results are presented. 1. INTRODUCTION A Digital Photogrammetric System (DPS) is made up of two different units: the Acquisition Unit (AU) and the Restitution Unit (RU). Fig. 1 - Logical structure of a Digital Photogrammetric System The AU permits one to produce the required images in digital form, in such a way that it is possible to associate the correct co-ordinates of the central perspective of the object to be sur- veyed to each pixel of the images. This means that all calibra- tions and the interior orientation (when necessary) of the im- ages must be performed by the AU that consist of a stand-alone solution of hardware and software which is completely inde- pendent of the RU that uses the digital images for the survey. The proposed definition differs from the generally accepted one of an acquisition unit for a traditional analytical photogram- metric system. In this case the acquisition unit produces photo- graphic images and only the use of the analytical plotter (the restitution unit) allows one to determine the central perspec- tive co-ordinates of the interesting points. The RU allows the individuation of the homologous points, helping the operator by means of the auto-correlation algo- rithms, the exterior orientation of the images and the computa- tion of the X, Y, Z co-ordinates of the chosen points. Very effective solutions of DPS have been presented over the last few years, based on ad-hoc hardware such as: high- resolution photogrammetric scanners (e.g. Photoscan PS1 by ZEISS, DSW 200 by Leica & Helava, VX3000 Plus by Vex- cel), digital photogrammetric cameras (e.g. UMK-SCAN by ZEISS, ROLLEI SCANPACK by ROLLET) and workstations that are able to manage a large amount of data in real-time (e.g. Phodis ST by ZEISS and Intermap 6487 by INTER- GRAPH and DPW 770 by Leica & Helava). At the same time significant effort has been made to investi- gate the possibility of using low-cost hardware, such as DTP scanners, amatorial digital cameras and PC based restitution units. The achieved results allow one to point out a Low Cost Digital Photogrammetric System (LC-DPS) which can obtain the required metric precision both in aerial and close-range application of photogrammetry. The feasibility study of a low cost RU has been presented by the author’s research group (Dequal, 1996). This paper de- scribes the structure of the AU that are devoted to close-range photogrammetric applications based on low-cost hardware and “ad-hoc” software, in detail. 2.DIGITAL ACQUISITION UNITS FOR CLOSE-RANGE PHOTOGRAMMETRY The AU can be classified on the basis of the digital images source. In direct AU digital images are directly acquired by means of a digital camera; in indirect AU digital images are produced by means of an hard-copy scanning process of photo- graphic images (metric, semi-metric or non metric). The digital images can be transmitted to the RU in two differ- ent Ways: e the digital image is associated to a calibration file contain- ing the analytical parameters that are useful to transform the rows and columns co-ordinates of the pixels into the x,y co-ordinates that refer to the inner system; e the digital image is re-sampled in order to automatically associate the corresponding x,y co-ordinates to each pixel and then send them to the RU. The first option is the quickest one, but the calibration file must consider all the requested formats by the different RU available on the market. The second gives images that can be directly managed by all types of RU but the re-sampling of the original image can lead to a loss of contrast and a non negligi- ble time for computations. In the author's opinion independence from the RU seems to be the most important feature, therefore in the following this kind of approach will be analysed. As far as the graphic formats are concerned, it is suitable to adopt both uncompressed (e.g., TIFF, BMP, TARGA) or com- 141

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