TopCAT—Topographical Compartment Analysis Tool to Analyze Seacliff and Beach Change in GIS

TopCAT toolbar and user interface in ArcGIS.

TopCAT toolbar and user interface in ArcGIS.

Computers & Geosciences, Volume 45, August 2012, Pages 284–292

Michael J. Olsen, Adam P. Young, and Scott A. Ashford

“This paper discusses the development of a new GIS extension named the Topographic Compartment Analysis Tool (TopCAT), which compares sequential digital elevation models (DEMs) and provides a quantitative and statistical analysis of the alongshore topographical change. TopCAT was specifically designed for the morphological analysis of seacliffs and beaches but may be applied to other elongated features which experience topographical change, such as stream beds, river banks, coastal dunes, etc. To demonstrate the capabilities of TopCAT two case studies are presented herein. The first case examines coastal cliff retreat for a 500 m section in Del Mar, California and shows that large failures comprised a large portion of the total eroded volume and the average retreat rate does not provide a good estimate of local maximum cliff retreat. The second case investigates the alongshore volumetric beach sand change caused by hurricane Bonnie (1998) for an 85 km section in the Cape Hatteras National Seashore, North Carolina. The results compare well (generally within 6%) with previous investigations. These case studies highlight additional information gained through performing a detailed, discretized analysis using TopCAT.”

Regional Morphometric and Geomorphologic Mapping of Martian Landforms

Computers & GeosciencesComputers & Geosciences, Volume 45, August 2012, Pages 190–198

Radu Dan Capitan and Marco J. Van De Wiel

“Initial mapping of the Martian surface, based on stratigraphic markers identified from Viking imagery, resulted in the demarcation of broad planetary scale geological zones. Recent advances in image resolution have established the presence of many smaller surface elements superposed on the older geological zones, thereby indicating younger surface morphologies that are in contradiction with the older mapping. Moreover, the stratigraphic mapping technique is subjective and relatively cumbersome because of its reliance on visual interpretation of images.

“In this paper a new analytical technique is developed which uses morphometric analysis of the Martian elevation map (MOLA data) to automate delineation and mapping of landforms at the regional scale. The analysis relies on altitude, local relief and local watershed clustering to delineate the landforms, and applies statistical clustering to identify structures with similar properties.

“As a case study, the technique is applied to Atlantis and Gorgonum basins. Comparison of the delineated features with landforms visible on high-resolution THEMIS images illustrates the accuracy of the morphometric technique in delineating and classifying surface structures, and also permits interpretation of the origin and evolution of the landforms. Our results also show that morphometric data and morphologic evaluation can be combined into a single interpretation of the distribution of surface patterns. A new geomorphological map of the study area is produced and contrasted with the existing stratigraphic map.”