Preface

Photogrammetry from aerial platforms has been recognized since the 20th century as an important technique to map aerial grades, cities and regions. The modalities known as terrestrial and short distance have also been used, although in lesser proportion, in architecture, to survey historical buildings and monuments.

The main characteristics of photogrammetry, which prevented its wider use in other fields or made it difficult, were the high cost of the equipment – including airplanes, special aerial or terrestrial cameras, support field equipment for topography and geodesy, restitution equipment, and the high labor costs of the highly qualified personnel, from university-educated supervisors to technicians. All steps of the process, from the planning phase and acquisition of photographs to the finalization of the product are composed of a succession of rigorous proceedings, which demand high precision and attention.

This scenario of high operational costs in photogrammetry started to change in the 1990's with the introduction of digital photogrammetry. Already, in the beginning of the second decade of the 21st Century, photogrammetric digital cameras of all sizes are available on the market with high performance computer programs in mapping, but also for specific applications in mechanics, medicine, physiotherapy and other industries. Digital photometry has brought about great gains in productivity and has facilitated its use.

Moreover, with the low cost digital equipment and the freely available advanced processing image programs in libraries, as well as the integration of new developments in the field of information science – computer vision, inertial sensors and GNSS (Global Navigation Satellite System) positioning, it is now possible to develop low-cost personalized solutions. Therefore, photogrammetry is now accessible to non-photogrammetry specialists, researchers, engineers and specialists in all areas who need tridimensional measurements, including those peculiar critical situations in which the object cannot be touched.

The objective of this book is to supply current information about questions and applications of digital photogrammetry. The initial chapters deal with subjects related to radiometric and geometric quality. Chapter one deals with the alterations landscape

#### XII Preface

colors suffer in aerial photographs and the methods for their correction. Chapter two deals with methods for eliminating the seam line in mosaics of terrestrial photographs with fish-eye lenses. Chapter three compares and analyzes the precision of planimetric and altimetric measurements in digitalized analogical images and authentic digital images.

The following chapters present examples of applications of terrestrial photogrammetry systems. Chapter four presents a system that can be used to measure the deformations of structural elements in civil engineering, mechanics, and to survey historical buildings. Chapter five shows how the combination of terrestrial, aerial and satellite photographs can be used together to document archaeological sites and historical buildings. Chapter six shows an example of sub-aquatic photogrammetry for archeological surveying and the possibility of recomposing forms of broken and incomplete pieces from a 3D reconstruction. These examples show the solutions adopted for various particular problems each application demands, so as to maximize the data supplied by photogrammetric processing, whether orthorectified images, vectorial designs or a coordinate list.

The editor and the InTech editorial team thank the authors for contributing their work, for the quality of the chapters, the care in proceeding with the revisions, and also to the companies and agencies of governments that made available the photographs, data and materials used in the various papers.

> **Dr Daniel Carneiro da Silva**  Department of Cartographic Engineering, Federal University of Pernambuco, Brazil
