This paper reports research carried out to develop a novel method of monitoring coastal change, using an approach based on digital elevation models (DEMs). In recent years change monitoring has become an increasingly important issue, particularly for landforms and areas that are potentially hazardous to human life and assets. The coastal zone is currently a sensitive policy area for those involved with its management, as phenomena such as erosion and landslides affect the stability of both the natural and the built environment. With legal and financial implications of failing to predict and react to such geomorphological change, the provision of accurate and effective monitoring is essential. Long coastlines and dynamic processes make the application of traditional surveying difficult, but recent advances made in the geomatics discipline allow for more effective methodologies to be investigated.A solution is presented, based on two component technologies -the Global Positioning System (GPS) and digital small format aerial photogrammetry -using data fusion to eliminate the disadvantages associated with each technique individually. A sparse but highly accurate DEM, created using kinematic GPS, was used as control to orientate surfaces derived from the relative orientation stage of photogrammetric processing. A least squares surface matching algorithm was developed to perform the orientation, reducing the need for costly and inefficient ground control point survey. Change detection was then carried out between temporal data epochs for a rapidly eroding coastline (Filey Bay, North Yorkshire). The surface matching algorithm was employed to register the datasets and determine differences between the DEM series. Large areas of change were identified during the lifetime of the study. Results of this methodology were encouraging, the flexibility, redundancy and automation potential allowing an efficient approach to landform monitoring.
Coastal change is a major issue in many regions of the world, and is often driven by geohazard processes such as landslides and rockfalls. Effective assessment of such phenomena is essential for successful management of coastal ecosystems, and is often reliant on GIS-based analysis. However, while it is crucial that multi-temporal datasets can be accurately registered to a common reference system, traditionally, the dynamic nature of the coastal environment has hampered this process. This paper presents a robust surface matching technique which overcomes the requirement for physical control points, and instead derives control directly from the DEM surfaces. Although surface matching procedures are well established, performance can be sub-optimal where the surfaces contain regions of difference, such as those associated with geohazard activity or vegetation effects. The crucial aspect of the least squares matching approach developed here, is the incorporation of a robust estimation function which allows the effects of surface discrepancies to be mitigated through outlier handling. Aerial photogrammetry is an established technique for coastal monitoring, and extensive archival collections exist. However, archival datasets are particularly affected by the difficulties associated with acquisition of ground control. Conversely, the maturing technique of airborne laser scanning is less influenced by such problems, and instead is capable of producing a high quality representation of coastal terrain. This paper describes the application of the robust surface matching technique to test sites located on the east coast of England.Photogrammetric DEMs are approximately oriented, before being matched to control surfaces derived from higher order datasets, including airborne laser scanning DEMs. The robust matching algorithm is shown to produce significantly improved results over ordinary surface matching.Analysis indicates the effectiveness of this technique for exploitation of archival datasets, revealing a signature of extensive geohazard activity over the twenty-five year study period. Robust matching of airborne laser scanning datasets has also enabled the quantification of short-term geohazard activity, demonstrating the flexibility of this strategy.
The quantitative assessment of restoration and tooth wear usually requires fixed reference points from which measurements are made. In longitudinal patient follow-up the loss or erosion of such points may preclude measurement and an alternative approach is to seek regions of coincidence and conflict in digital models of before and after wear surfaces, with a continuous refinement of the parameters of the coordinate transformations, until the closest correspondence between them is found. A computer program has been written to implement the algorithm and assess the technique's capacity to find the match between surfaces both artificially generated and from tooth replicas recorded from patients at different epochs. The program was able to achieve the desired ends, demonstrating the utility of the technique in tooth wear assessment but identifying the need to refine the program further to enhance both its difference detection capabilities and level of automation. Examination of the theory and practical experience highlighted certain situations when user understanding is invaluable to ensure a satisfactory solution. This strengthened the investigators' resolve against reliance upon commercially based surface fitting programs whose basis may not be fully understood. Notwithstanding this surface matching is a powerful tool in the investigation of dental wear.
Since the earliest days of photogrammetry, there have been photogrammetrists who have directed research effort towards medical measurement. Although the specific motivation for these studies has not always been disclosed, it is probably because of the various benefits that photogrammetry can offer to humanity as a painless and non-invasive means of providing medical practitioners with spatial measurement relating to the human body. The intention of this paper is to reflect on the place of the many medical developments within the photogrammetric world. The various photogrammetric applications in medicine are
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