Integration of Terrestrial Laser Scanning and UAS Photogrammetry in Geological Studies: Examples from Croatia

Abstract

Terrestrial laser scanning (TLS) in combination with Unmanned Aircraft System (UAS) and modern computer based photogrammetry is currently the best approach for the acquisition of high-resolution 3D spatial information. Highly realistic 3D spatial data sets are becoming the basis for detailed geological studies, providing a multidisciplinary approach in the study and research of both underground and above ground sites. To emphasize the variety of possible implementations of these state-of-the-art methodologies, four characteristic and yet quite different case studies are presented where such geodetic techniques are successfully employed. The presented case studies demonstrate that TLS and UAS photogrammetry, as non-contact surveying methods, are able to reduce survey time and total project costs. As added value, they provide high-resolution data that can be analyzed in a virtual environment from a sedimentological or structural aspect. Stored digital documentation also allows future multi-temporal spatial data comparison at any timeframe and scale, thus enhancing any target geological data gathering and analyses at the studied sites.

Autonomous Vehicles Mapping Plitvice Lakes National Park, Croatia

“…A high-resolution georeferenced orthophoto image based on the camera images of the unmanned aerial vehicle (UAV) was used as a basis for the planning of survey missions, as shown in Figure 7. The methodology to generate such a large-scale orthophoto is partly described in [42]. This model was calculated before the bathymetry survey missions to serve as a crucial input for the safety of the ASV PlaDyBath.…”

UAV Photogrammetry and 3D Modelling of Complex Architecture for Maintenance Purposes: the Case Study of the Masonry Bridge on the Sele River, Italy

“…The SfM/MVS software used in the several tests and for the survey of the masonry bridge was Agisoft Metashape because it is a reliable and widely used photo-processing software, as shown in various works present in the literature [19][20][21]. The procedure that allowed obtaining the 3D model from images can be summarized in the following main steps [22]:…”

Spatial Data Performance Test of Mid-cost UAS with Direct Georeferencing

“…Unmanned vehicles are a very popular topic that has found its application in various areas of human exploration. Nowadays, there are many different Unmanned Aircraft System (UAS) solutions on the market, which are commercially available and can be used for high-resolution geodetic surveying and mapping [1,2]. Most of these systems are equipped with Global Navigation Satellite System (GNSS) receivers using stand-alone and differential codephase ambiguities correction solutions.…”

“…Most of these systems are equipped with Global Navigation Satellite System (GNSS) receivers using stand-alone and differential codephase ambiguities correction solutions. With these receivers, it is possible to determine the initial position of images with a meter or sub-meter level of accuracy [2]. In order to achieve survey-grade accuracy of few centimetres with such systems, and to produce high-resolution spatial data derived information such as the orthomosaic, digital elevation model (DEM) or point cloud it is necessary to stabilize and measure ground control points (GCPs) [3].…”

“…GCPs can be made in different shapes and sizes, depending on altitude and Ground Sample Distance (GSD) or required accuracy. Accuracy of GCPs directly affects the accuracy and quality of the processed data and final output [2][3][4][5]. A total station (TS) can be used for determination of GCPs with millimetre level accuracy.…”