Dimitra Vassilaki

Matching and Evaluating Free-form Linear Features for Georeferencing Space-borne SAR Imagery

ing geometry and the absence of true colour. This is not necessarily a drawback for the SAR images; contemporary SAR sensors may not need control information for orientation processes due to accurate orbit data (Vassilaki et al. 2011a). It is more a problem of the coprocessing (combined/synergistic use) of slant range (not geometrically corrected) SAR data with heterogeneous (multimodal and multitemporal) remote sensing and geospatial data, in the sense of identifying salient points to correlate the other data with SAR. The concept of co-processing SAR data with other data types is of growing signiicance (söRgel et al. 2008, WegneR et al. 2009, sURi & ReinaRtz 2010, Vassilaki et al. 2011b,WegneR et al. 2011, ReinaRtz et al. 2011). There is a worldwide abundance of readily available geospatial informa

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.