Abstract
Abstract. The technology of airborne laser scanning enables fast and accurate gathering spatial data containing also echoes from the terrain below the vegetation canopy that is beneficial for topographic mapping of wooded sandstone landscapes in Czechia, Poland, and Germany. The challengeable task is to determine the ground points in the point cloud because commonly used filtration methods do not successfully distinguish between vegetation and rock pillars and faces. In this paper, we replace filtration with classification approach using the features derived from characteristics of points within a neighbourhood of optimized sizes, such as eigenvalue-based features and echo ratio. Random Forest classifier is trained and tested on the manually labelled dataset with a density of almost 650 points/m2 from the Adršpach-Teplice Rocks. The overall accuracy reaches 87% but recall and precision of non-ground points are unsatisfactory. Misclassified non-ground points are located also within trees, thus we do not consider the result as suitable for DTM processing without further processing.
Highlights
The sandstone phenomenon forms an unusual landscape in the northern part of Czechia and extends beyond the borders of Germany and Poland (e.g. Bohemian and Saxon Switzerland, Stołowe Mountains, Adršpach-Teplice Rocks)
A part of them are probably very low thickets and herbal cover which is difficult to separate from the ground even manually because there are no echoes from the ground below them
The experiment presented in this paper mostly follows a traditional approach of point cloud classification, but applied on the unusual dataset
Summary
The sandstone phenomenon forms an unusual landscape in the northern part of Czechia and extends beyond the borders of Germany and Poland (e.g. Bohemian and Saxon Switzerland, Stołowe Mountains, Adršpach-Teplice Rocks). In its wildest form, the landscape is called “rock cities” due to the similarities of steep walls and deep and narrow gorges with buildings along the streets in human-made towns. Passable terrain together with the fact that in climatic conditions of the central Europe the sandstone areas are covered with dense vegetation complicate topographic mapping of these regions. The airborne laser scanning (ALS) is a suitable method for topographic mapping in wooded areas as it allows for gathering data about the shape of the terrain below vegetation. The more challengeable part of dealing with ALS data is the processing because the categorization of object types, which the echo comes from, is not a trivial task. A lot has been discussed about the filtration aiming to select the ground points but commonly used algorithms (Axelsson, 2000; Kraus and Pfeifer, 1998) tend to smooth the rock formations or imperfectly filter out the vegetation points, depending on parameter settings (Lysák, 2016; Tomková, 2018)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
