Application of NEXTMap DEM Data to the Mapping and Interpretation of Late Quaternary Landforms in the Scottish Highlands

This thesis examines the potential of NEXTMap imagery for the study of glacigenic landforms in parts of the Scottish Highlands. NEXTMap Digital Elevation Mapping (DEM) was developed in 1998 and a comprehensive set of DEMs for the British Isles generated in 2004. However, very few maps based on NEXTMap technology had been published for the British Isles before the start of this PhD, and so its full potential had not been realised. The objectives of the PhD were therefore to establish the degree to which NEXTMap imagery could improve the mapping of Quaternary landforms.

To test its capabilities, NEXTMap images were obtained for the Loch Lomond area, which had previously been mapped in some detail using both field observation and aerial photography. Appropriate protocols were therefore developed for an area where NEXTMap images could be ‘ground-truthed’ by independent ground mapping. Methods were developed for optimizing the appearance of landforms on NEXTMap images and mapping their distributions; the results show close correspondence with the results of detailed ground mapping, suggesting that confidence can be attached to landform maps derived using NEXTMap, while the latter can also provide subtle but important new geomorphological information.

The second part of the thesis applied the methodology developed in the Loch Lomond study to the study of landforms in and around Glen Roy, in the western Scottish Highlands. This area was chosen as it also had already been mapped in detail and proved to be critical for establishing the extent and timing of the last major glaciers in Scotland. The area also contains a unique set of well preserved ancient lake shorelines – the Parallel Roads of Glen Roy. These features extend for miles across the study area, providing an outstanding opportunity to test the spatial and vertical resolution of NEXTMap images, and hence to establish the limits of maps and models based upon them. This part of the project included direct tests of the vertical resolution achievable using NEXTMap, which gives surprisingly accurate data for flat and gently-inclined surfaces. The results of trend surface analysis of nearly 32,000 altitude measurements obtained from the shoreline surfaces shows that despite the fact that they are significantly deformed and dislocated, they nevertheless retain consistent along-shore surface gradients. Both the overall gradients and the localized deformation features associated with the shorelines are attributed to a combination of regional and local isostatic stresses. The thesis finishes with a synthesis of the new evidence and perspectives that NEXTMap has provided for the Glen Roy area, and with a synopsis of where interpretations differ from those previously based on ground mapping.