The collection of solid waste is a challenging issue, especially in highly urbanized areas. In developing countries, landfilling is currently the preferred method for disposing of solid waste, but each landfill has a limited lifecycle. Therefore, changes in the amount of stored waste should be monitored for the sustainable management of such areas. In this study, volumetric changes in a landfill were examined using a low-cost unmanned aerial vehicle (UAV). Aerial photographs obtained from five different flights, covering approximately two years, were used in the volume calculations. Values representing the amount of remaining space between the solid waste and a reference plane were determined using digital elevation models, which were produced based on the structure from motion (SfM) approach. The obtained results and potential of UAVs in the photogrammetric survey of a landfill were further evaluated and interpreted by considering other possible techniques, ongoing progress, and the information existing in an environmental impact assessment report. As a result of the study, it was proved that SfM carried out using a low-cost UAV has a high potential for use in the reconstruction of a landfill. Outcomes were obtained over a short period, without the need for direct contact with the solid waste, making the UAV preferable for use in planning and decision-making studies.

The discontinuity and roughness properties of the rocks can be used to obtain information on surface characterization. In this study, it was investigated whether the discontinuity and roughness properties of the rock structure are related to the temperature of the surface. Selected object which is located at Istanbul Technical University Ayazaga Campus has approximately dimensions of 3 m x 1 m. The discontinuity regions on the object and the areas which are rougher than their surroundings are clearly identifiable by visual interpretation. 3D model of rock surface was produced by integrating photographs and 12 control points which were homogeneously distributed on the object in order to reflect the surface realistically. The temperature of the control points marked on the surface were measured by using an infrared thermometer with non-contact measuring capability. These values were used as the basic data to show the temperature distribution over the entire surface. Temperature distribution map with 6 classes representing the temperature range was produced by using IDW interpolation method in a commercial GIS software. The temperature distribution map was overlapped on the 3D object model produced by means of RGB photographs for comparison with the 3D model produced by the thermal images of the same surface. The temperature distribution in the discontinuity regions that can be clearly seen as rough was examined and obtained results proved that there is a strong relationship between roughness and temperature of the rock surfaces.

No abstract

Low-level cameras are generally used in low-cost UAVs employed for photogrammetric product generation. Although such cameras have advantageous features in terms of flight time and maneuverability thanks to their light weight in a compact structure, they have also some limitations. These sensors are generally operated by rolling shutter which affects the image geometry. Unlike global shutter, a camera with rolling shutter creates the photograph by scanning line by line. In this study, two flights were performed by means of DJI Phantom 4 Pro to investigate the rolling shutter effect on the accuracy of photogrammetric product. Study area was a part of approximately 60 ha of Tasliciftlik Campus, Tokat Gaziosmanpasa University. Average speeds of the platform during photography were 8 m/sec and 12 m/sec. Obtained data were evaluated according to SfM workflow. The orthophotos of the study area were produced from aerial photographs both with and without rolling shutter correction by using photogrammetric software. 24 ground control points located in the study area were used to strength the model and to make accuracy assessment. According to the results, total root mean square error values were improved from 6.33 cm to 4.78 cm and 7.01 cm to 4 cm for the flights pertaining to the 8 m/sec and 12 m/sec, respectively. Thus, it can be said that better accuracy values can be obtained when rolling shutter correction are implemented during the process. Lower speeds may require multiple flight tasks depending on the extents of the study area. Therefore, it is more reasonable to fly at higher speeds and then apply rolling shutter correction to complete field work in less time.

No abstract