Geographical studies and environment protection research
Volume X | Issue 1
Application of Object Based Image Analysis for Glacial Cirques Detection. Case Study: The Ţarcu Mountains (Southern Carpathians)
Abstract: Geomorphologic mapping is an important fact in many research studies and the traditional methods are time consuming and expensive. This paper aims to develop a semi-automated rule-based method for the detection of glacial cirques for a test area located in the Ţarcu Mountains (Southern Carpathians) in an object-oriented approach. In this study we have established the morphometric characteristics of the glacial cirques developed in a particularly geomorphologic context at the edge of planation surfaces, using a 10 m horizontal resolution DEM (Digital Elevation Model). The parameters extracted from DEM (i.e. curvature) were further used in segmentation and classification process. Also, other factors were introduced in the rule set, as the context regarding neighboring objects like planation surfaces to the target class. The most important factor in segmentation was the curvature and to choose an appropriate scale factor we have used the available ESP (Estimation of Scale Parameter) tool. The results achieved were very close to the field reality, except for some areas where there are large negative landforms such as gullies and torrents, which were identified as objects belonging to glacial cirques class and also some roches moutonnées with high positive curvature values, objects that could be filtered manually by the user based on previous field knowledge and ancillary data such as orthophotoplans and the geomorphologic map of glacial relief in the Ţarcu Mountains. For further research, we intend to identify the characteristic thresholds for morphometric parameters that can be integrated in a set of rules in order to detect and classify other type of landforms in the alpine domain of the Ţarcu Mountains.
Volume VIII | Issue 8
The Semiautomated Identification of the Planation Surfaces on the Basis of the Digital Terrain Model. Case Study: The Mehedinti Mountains (Southern Carpathians)
Abstract: The paper presents a method for the semiautomated classification of the planation surfaces, using the Digital Terrain Model (DTM) and the object-oriented analysis. The effort undergone for developing such a method has a number of motivations. The first one is that these landforms are very important for decoding the geomorphologic evolution of the relief units. The second motivation concerns the fact that their identification and mapping, by using classical means, represents a difficult demarche, which requires a lot of time. Finally, the already-known limits of the relief analysis using the DTM at pixel level impose the testing of an object-oriented analysis, in which the area under study is divided into objects of various dimensions, as homogenous as possible from the viewpoint of one or more properties. The method that we propose supposes the following steps: the realisation of the slope model and of the flow model, starting from the DTM; the division, by segmentation into objects that are as homogenous as possible from the viewpoint of the slope; the classification of the objects into landforms (planation surfaces) by using the fuzzy functions and taking into account more factors simultaneously (the average slope value, the minimum slope value, the flow coefficient and the altitude), and the selection and grouping of the identified surfaces into sculptural complexes. The first stages represent the automated part of the method, while the last one requires a detailed geomorphologic analysis of the area, as well as the validation of the results on the field. The method was firstly developed for the Godeanu Mountains, the map of the levelled surfaces (Niculescu, 1965) being used for the identification of the parameters included in the algorithm, as well as for testing the results obtained in the view of the improvement of the method. Due to the good results thus obtained, the same method was also used for mapping the levelled surfaces in the Mehedinţi Mountains, and, along with the field observations, there was realised the planation surfaces map for this relief unit.