CLOSE RANGE DIGITAL PHOTOGRAMMETRY TECHNIQUES APPLIED TO LANDSLIDES MONITORING
This paper deals about the use of non metric reflex digital cameras in landslide monitoring and the analysis of landscape evolution from comparison of present digital photographs and old digitized analogue metric terrestrial photographs. The methodology has been improved in a test area (a slope along a road with instability processes in southern Spain) where terrain failures have been documented in the last ten years. Several photogrammetric techniques were checked as well as combination of both convergent (for calibration and densification) and stereoscopic (for DTM generation) networks. Considerations about the use of terrestrial LIDAR and a comparative example are also made. This paper is included in a wider research project carried out in Northern and Southern Spain for study landslides. This research project (MAPMUT: The improvement of susceptibility analysis by means of useful digital models of the terrain geometry), aims with an improvement of susceptibility maps using high quality input information.
Correlation of multi-temporal ground-based images for 1 landslide monitoring: application, potential and limitations.
Title: Correlation of multi-temporal ground-based images for landslide monitoring: application, potential and limitations. Article Full Abstract 16 The objective of this work is to present a low-cost methodology to monitor the displacement of 17 continuously active landslides from ground-based optical images analyzed with a normalized 18 Image Correlation technique. The performance of the method is evaluated on a series of images 19 acquired on the Super-Sauze landslide (South French Alps) over the period 2008-2009. The 20 image monitoring system consists in a high resolution optical camera installed on a concrete pillar 21 located on a stable crest in front of the landslide and controlled by a datalogger. The data are 22 processed with a cross-correlation algorithm applied on the full resolution images in the 23 acquisition geometry. Then, the calculated 2D displacement field is ortho-rectified with a back 24 projection technique using a high resolution DEM interpolated from Airborne Laser Scanning 25 (ALS) data. The heterogeneous displacement field of the landslide is thus characterized in time 26 and space. The performance of the technique is assessed using as reference differential GPS 27 surveys of a series of benchmarks. Because the proposed methodology can be routinely and automatically applied, it offers 33 promising perspectives for operational applications like, for instance, in early warning systems.
Comparative camera calibrations of some 'off the shelf' digital cameras suited to archaeological purposes.
The increasing availability and capability of "off the shelf" low cost digital cameras coupled with on-going advances in mobile computing technology offer great potential for on-site archaeological recording. In particular the userfriendliness and ready availability of these systems coupled with image orientated modelling software packages such as Photo Modeller and Photo Builder are providing systems that are increasingly suited to the requirements of on-site archaeological recording. However, whilst offering ease of use, the geometric performance and imaging stability of all "off the shelf" systems are extremely dependant on the manner in which they are used and the selection of an appropriate calibration method. This paper, through a series of calibration experiments, investigates the suitability and geometric stability of three such camera systems: a pair of Kodak DC210 cameras, a pair of Kodak DC260 cameras and a Canon DV1 digital video camcorder used in both still and video imaging modes. The work undertaken demonstrates that all three systems are capable of attaining measurements to sub-pixel accuracy provided that the image acquisition methodology adopted for each camera takes into account and compensates for the particular design features of each system. In particular it is noted that some of the design features aimed at promoting ease of "snap shot" photography must be circumvented if camera internal geometry is to remain at best stable or at least reproducible.