Unmanned Aerial Vehicles (UAVs) can be used to acquire highly accurate data in deformation survey, whereby low-cost digital cameras are commonly used in the UAV mapping. Thus, camera calibration is considered important in obtaining high-accuracy UAV mapping using low-cost digital cameras. The main focus of this study was to calibrate the UAV camera at different camera distances and check the measurement accuracy. The scope of this study included camera calibration in the laboratory and on the field, and the UAV image mapping accuracy assessment used calibration parameters of different camera distances. The camera distances used for the image calibration acquisition and mapping accuracy assessment were 1.5 metres in the laboratory, and 15 and 25 metres on the field using a Sony NEX6 digital camera. A large calibration field and a portable calibration frame were used as the tools for the camera calibration and for checking the accuracy of the measurement at different camera distances. Bundle adjustment concept was applied in Australis software to perform the camera calibration and accuracy assessment. The results showed that the camera distance at 25 metres is the optimum object distance as this is the best accuracy obtained from the laboratory as well as outdoor mapping. In conclusion, the camera calibration at several camera distances should be applied to acquire better accuracy in mapping and the best camera parameter for the UAV image mapping should be selected for highly accurate mapping measurement.
Terrestrial laser scanner (TLS) is a non-contact sensor, optics-based instrument that collects three dimensional (3D) data of a defined region of an object surface automatically and in a systematic pattern with a high data collecting rate. This capability has made TLS widely applied for numerous 3D applications. With the ability to provide dense 3D data, TLS has improved the processing phase in constructing complete 3D model, which is much simpler and faster. Pre-processing is one of the phases involved, which consisted of registration and georeferencing procedures. Due to the many error sources occur in TLS measurement, thus, pre-processing can be considered as very crucial phase to identify any existence of errors and outliers. Any presence of errors in this phase can decrease the quality of TLS final product. With intention to discuss about this issue, this study has performed two experiments, which involved with data collection for land slide monitoring and 3D topography. By implementing both direct and indirect pre-processing method, the outcomes have indicated that TLS is suitable for applications which require centimetre level of accuracy.
One of the major problems affecting municipalities is solid waste management. There is a difficulty in selecting suitable sites for waste disposal as it involves different factors to be considered before site selection. Currently, waste generation in Johor Bahru has steadily increased over the last few years and the only existing sanitary landfill is reaching its capacity limits, which means that a new sanitary landfill site needs to be constructed. In this study, geographic information system (GIS) and analytical hierarchy process (AHP) methods were utilized with the integration of dynamic data such as future population and projection of waste production in order to provide suitable sites for the construction of a sanitary landfill in the study area. Thirteen criteria were considered for this study, namely water bodies, soil, geology, slope, elevation, residential areas, archeological sites, airports, population, road, railway, infrastructure, and land use. AHP was used to determine the weights for each criterion from the pairwise comparison matrix. Consistency index and consistency ratio were checked and confirmed to be suitable. The results obtained from AHP were assigned to each criterion in GIS environment using weighted overlay analysis tool. The final potential site map was produced, and the three most suitable potential landfill sites were identified.
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