Athanassios Stamos

Exploitation of satellite optical and SAR data for public work studies

This paper studies the use of high resolution satellite optical and SAR images for 1:5,000 mapping production, which is essential for public work and environmental impact assessment studies. The images were used for the extraction of DEMs and their “fit for purpose” use was investigated, through the examination of parameters like accuracy, reliability and performance of morphological features. Orthoimages from satellite optical images using the produced DEMs with or without breaklines were produced. An application was developed on Antiparos island, a Greek island with irregular terrain. The data includes: (a) a triplet of Pleiades (1A, tri-stereo) satellite images, with a resolution of 0.5m, (b) a TanDEM-X Intermediate DEM, a preliminary version of the forthcoming TanDEM-X global DEM, and (c) an accurate DEM produced from the Greek National Cadastre & Mapping Agency S.A. was used as the reference DEM. The georeferencing of the optical images was computed using GCPs which were measured with GNSS. DEMs were extracted using all the possible combinations of the images triplet using automated image matching without any filtering or editing and were evaluated using the reference DEM. The combination of images which yielded the best DEM was then used to manually editing 3D points and collecting breaklines in order to produce a better DEM, which was also evaluated using various statistical measures and geo-morphological features. Orthoimages were created and evaluated using DEMs from optical and SAR data. A discussion about the use of the computed mapping products for the various stages of the public work studies is included.

Computer-Aided Analysis of Pedestrians’ Motion Behavior Using Video Frames

This chapter aims to present the evolution of technical software which decodes the behavior of people who walk in the urban environment. It uses and analyzes video frames of a region which are recorded by a stationary, run-of-the-mill video camera. The software is able to track semi-automatically the motion of targets in a region of interest and produce the route of the targets in a drawing environment and in a world coordinate system. The photogrammetric Direct Linear Transform (DLT) method with known terrain is used to extract the information from single video frames, simultaneously correcting the nonmetric cameras’ systematic errors. The Least Squares Method is employed to achieve increased accuracy.

The Influence of Weather Conditions on Pedestrians’ Behavior and Motion, with Respect to Queues in Outdoor Urban Areas

The purpose of this chapter is to examine the influence of weather conditions on the behavior and motion of pedestrians, with respect to queuing in outdoor urban areas, exposed to changes in weather conditions. It aims to extract useful conclusions for the rational design of urban spaces in locations of pedestrian access and circulation (squares, entrance–exit of public spaces, open-air markets, etc.). The research includes the recording and analysis of characteristic pedestrian motion parameters, for two different years, in exactly the same space, and under similar evolution characteristics of the event and the service of the pedestrians in the queue. The only marked difference was the weather conditions prevailing in the area.