Journal of Surveying Engineering

Nowadays, obtaining large-scale topographic maps from unmanned aerial vehicle (UAV) photogrammetric projects has become an alternative to traditional surveys based on global positioning systems (GPSs) or total stations. This assumption is based on the reduction of costs, the application to reduced zones, the efficiency of the procedures, and the positional accuracy achieved, etc. In this context, this study analyzes and compares the lines obtained from two sources: a global navigation satellite system–real-time kinematic (GNSS-RTK) survey and an UAV photogrammetric project. Usually, the GNSS data set of lines has a higher positional accuracy, whereas the UAV data set has a richer geometry. The proposed methodology realizes several positional controls (based on lines) to analyze the positional accuracy of the UAV data set of lines and the geometrical representability of the GNSS data set of lines. In addition, an improvement in the representation of lines with poor geometry is suggested by using a hybrid model composed of splines and straight segments. The application is implemented using more than 11 km of lines obtained from both sources. The results confirm the viability of the positional control based on lines, the sufficient accuracy of lines obtained from the UAV to be used for maps at large scales, and the improvement in the representability of the proposed hybrid model.

The main goal of this paper is to present a new method of staking out the interior elements of a monopile tower. The stake out is conducted during the construction of a monopile. The proposed method uses geodetic equipment instead of standard measuring tapes. It describes all the necessary computations and accuracy analysis. The coordinate frame used in the design is referenced to a virtually existing monopile axis. This paper describes the idea of using the centers of the monopile rims to reference the stake out as well as the necessary transformations from the design to the stake-out coordinate frames. The accuracy analysis performed in the paper confirms the possibility of the presented method application. The key measurement parameters are described along with their required accuracies. The final form of the stake-out parameter equations is derived. In addition, some practical considerations, such as the design of the prism holder and description of the stake-out procedure from the perspective of the operator, are included.

The geodetic datum of a deformation monitoring network is defined using its reference points. This article discusses how deformation analysis is affected when reference points have been displaced as a result of rigid body displacement (translation and rotation) and deformation (extension or contraction) of the reference block; this article also includes points with single-point displacements. With this aim, the effects of the displacements of the reference points on the estimated displacements of the network points are considered. The well-known similarity (S)-transformation matrix associated with network datum is a convenient projector for explaining these effects. Some horizontal and vertical monitoring network examples are used to discuss the effects of the displaced reference points on deformation analysis.

Minimal detectable bias (MDB) describes a system’s general ability to detect the existence of a single outlier. However, successful identification probability is closely related to the correlations between w-statistics. When the correlation is high, the validity of the MDB as a system internal reliability index is weakened. Based on the correlation coefficient, the probabilities of committing missed detection and wrong exclusion can also be estimated; however, the latter might be significant, inducing obvious discrepancies between the actual successful identification rate and the preset value dominated by the MDB. In this paper, given a threshold to the probability of wrong exclusion, a minimal separability bias (MSB), usually larger than the MDB, is obtained using an analytic method, which can control both the probability of missed detection and of wrong exclusion. Compared with previous work, the MSB described here is expressed by an algebraic formula, which simplifies the calculation and promotes its practical application.

The presented paper focuses on the interregional usage of unmanned aircraft systems (UAS) for infrastructural inspection as well as structural health monitoring (SHM). These aerial sensor platforms are used for the inspection of bridges that are difficult to access and distinguished by their height, location, or a combination of both. The UAS inspection is performed by visual cameras or thermal imagers for state detection, whereas object contours are scanned by LiDAR to allow precise close-range inspection and trajectory control. There are challenges in maintaining the precise laser distance control at the infrastructure, such as the LiDAR sensor measurement accuracy and infrastructural and environmental conditions. The presented bridge-specific flight pattern navigation is an essential trajectory planning tool for acquiring reproducible inspection data and its quality. Based on the UAS inspection data, ultrahigh resolution reconstructions of every part of an object are built in terms of two-dimensional (2D) projections before being postprocessed in a full three-dimensional (3D) building model. These models are then integrated into a web-based geographic information system platform developed within the project. It provides georeferenced implementation and visualization of the inspection data as well as all data concerning ongoing and scheduled construction planning or any other building documentation.

The standard method in surveying practice for adjusting mobile terrestrial laser scan (MTLS) data to correct for global navigation satellite system (GNSS) positioning errors consists of placing a detailed network of surveyed control targets along the corridor being scanned. Although this approach is easy to understand and implement, it is suboptimal with regard to accuracy, efficiency, and safety. Fortunately, the rapid data acquisition that characterizes MTLS enables the user to quickly obtain repeated independent measurements, providing a simple method to examine potential errors that may be present in an individual pass. These multiple passes can be statistically combined and input with GNSS and inertial measurement unit (IMU) data to allow adjustment of the vehicle trajectory. This paper investigates this new multipass approach (MPA) of collecting and processing MTLS data, which reduces control requirements, resulting in significant improvements in accuracy and economic and safety benefits. In this paper, two case studies using MPA are discussed, and the obtained data are analyzed to demonstrate the effectiveness of the MPA. In one of the case studies, GNSS conditions were poor; in the other case study, GNSS conditions were ideal. From these cases studies, the appropriate intervals for control targets were determined based on the desired level of accuracy. In both cases, the multipass approach was shown to be effective in significantly improving accuracy and reducing the need for dense control target networks.

Surveying in an undergraduate civil engineering curriculum needs a substantial amount of hands-on training to obtain adequate learning outcomes. A lecture-only mode of delivery does not provide the adequate surveying skills needed by an engineering student. In 2009, workshops were introduced for the CVEN2000 Civil Engineering Drawing and Surveying unit at Curtin University, Australia, with the aim of offering students hands-on training in surveying to enhance their learning. This study analyzes data collected from 160 students in 2012 and 2013 using confidence limits, correlations, frequency percentage distribution, and principal component analysis to evaluate if the introduced workshops contributed to the enhancement of (1) the students acquiring industry-based skills and (2) the students’ overall learning of engineering surveying, which is a practical-oriented course. Additionally, qualitative analysis from Curtin’s official eVALUate and examination results were used to verify the findings of the previously mentioned contributions. The results indicate that workshops contributed to the development of the students’ overall learning skills, with the top agreement of the students being critical thinking skills (93.6%), handling problems (96.6%), and correlating theory (97.9%). Qualitative analysis of the 2013 data indicates that 70% of the students agreed that their overall learning skills were enhanced and that the workshop sessions prior to the assessed fieldwork of setting out the horizontal curves enhanced their communication and teamwork skills. Overall, 97.9% of the students were satisfied with the workshops, and 98.9% of the students said that they would recommend them as an effective learning tool to their friends. The main lesson learned from the data presented in this paper is that students were satisfied with the workshops and recognized/perceived them to contribute to the development of the learning attributes they need to acquire.

This paper presents an attempt to reduce positional errors in digital cadastral maps produced by digitization (scanning, georeferencing, and vectorization) of existing Bosnian-Herzegovinian analog (paper-based) maps. The geometric content of the digital cadastral maps generated by the aforementioned procedure is encumbered by nonuniform and irregularly distributed positional distortions. Errors created during the original elaboration of the analog maps (based on hand drawings using the drafting instruments) cannot be corrected through the geometric transformation of the cadastral map with the use of common (tie) points on the map coordinate grid. This study focused on the elimination of errors in the original map drafts through better selection of common points, with the aim of obtaining a homogeneous spatial accuracy of cadastral maps. With the use of the flexible thin plate spline (TPS) transformation model, which includes information on systematic distortions caused by errors of the original mapping process, the authors made a significant step toward the enhancement of the positional accuracy of boundary points in the digital cadastral maps. The use of TPS transformation reduces heterogeneity of each cadastral map, and maps are efficiently georeferenced to the state plane coordinate grid. Digital cadastral maps generated by reconstruction of original state survey measurements are typically more accurate than those obtained by digitizing scanned maps, and these types of maps were not considered in this study.

Shoreline monitoring is essential for integrated coastal zone management (ICZM). It provides the necessary information needed to manage the settlement of coastal areas, establishes guidelines for management of socioeconomic activities within the coastal areas, provides information necessary for recovery actions of beach regeneration, and provides a reference baseline for studies related to climate change in coastal zones. Shoreline monitoring methods are largely dependent on goals, costs, implementation, and applicability. For monitoring of short coastal shorelines (e.g., tens to hundreds of kilometers), global navigation satellite system (GNSS)-based methods are emerging as low-cost approaches that offer rapid, weather-independent, and quickly updatable products that could benefit policy makers when high costs of traditional methods, such as photogrammetry and remote sensing, are of concern. However, various GNSS methods applicable to shoreline monitoring exist, making it difficult for decision makers to choose a suitable approach. Using a case study of the Pernambuco State ICZM in Brazil, this study evaluates three of the most commonly used GNSS-based shoreline monitoring methods, that is, relative kinematic (RK), real-time kinematic (RTK), and precise point positioning (PPP) methods. It also provides a comprehensive analysis of their strengths and limitations. The results highlight the issues and important considerations in choosing an economically viable GNSS method for mapping shoreline changes, particularly for supporting ICZM policies.