Journal of Surveying Engineering

Horizontal curve identification is important both for road safety management and railway maintenance. Parameters of a transition curve are introduced to perform an orthogonal least-squares fitting. During such a fitting process, the Gauss-Newton (GN) method may fail to converge because of an ill-conditioned Hessian matrix. A biobjective fitting model is introduced, and the Levenberg–Marquardt (LM) algorithm is specified to perform the fitting of transition curves. The LM parameter is updated heuristically during iterations according to the specific information explored instead of the standard preset way. Further, another heuristic strategy is proposed to search a path to the optimum instead of the traditional greedy strategy. The heuristic strategies were compared with traditional ones by fitting a transition curve of a railway to the measured points. Monte Carlo simulations were employed to test the robustness and efficiency of the modified LM algorithm, with different initial values, all converging to the same optimum. Results showed that the heuristic strategy for updating the LM parameter has a better robustness than the preset way, and the heuristic strategy for searching a path converges much faster than the traditional one, for which visual interpretations are provided.

Utilizing charge-coupled device (CCD) imaging technology in astronomical surveying and positioning facilitates high-precision measurements without manual observation. This eliminates the influence of the traditional celestial geodetic personal and instrumental equation, and further improves measurement efficiency and automation. This paper proposes a CCD astronomical measurement method based on a Leica video georobot platform and a polynomial transformation method based on circle readings to achieve rapid and accurate conversion between circle and pixel coordinate differences. The RMS error (RMSE) of the horizontal and vertical transformations is better than 0.7′′ and 0.6′′, respectively. The results of initial astronomical field observation experiments indicate that the average internal precision in the longitudinal and latitudinal directions is better than 0.015 s and 0.20″, respectively, and the RMSE of external accuracy is better than 0.02 s and 0.30″, respectively, which proves that the proposed method is reliable and accurate when conducting first-class astronomical surveys. Furthermore, the proposed method reduces workflow and field operation times and facilitates miniaturization and automation, and makes high-precision astronomical field measurements rapid and intelligent.

Least-squares (LS) techniques have been a frequent choice advocated by a plethora of engineers for modeling problems requiring a unique solution based on sets of redundant observations perturbed by random noise. In this paper, several versions of LS procedures using the general quadric polynomial equation as the math model are reviewed and applied to a triaxial ellipsoid fitting exercise. The coefficients of this polynomial are then transformed into the nine parameters defining the spatial properties of the ellipsoid: semiaxes, coordinates of the origin, and rotation angles. Finally, a novel methodology requiring eigentheory is introduced to complete the determination of the variance–covariance matrices of these parameters.

Unmanned aerial systems (UASs) are an emerging technology being used in many fields, including surveying engineering. When UASs are used for these activities, they may operate in close proximity to active traffic. UASs could be distracting to drivers and increase safety concerns in these situations. Currently, there are no temporary traffic control (TTC) signs approved by the Manual on Uniform Traffic Control Devices (MUTCD) to specifically inform drivers of roadside UASs. For this study, new UAS TTC signs were designed and a questionnaire was developed to explore perspectives on UAS specific TTC. Participants drove in a high-fidelity driving simulator, which measured speed reduction, as participants drove past various configurations of TTC elements in advance of a roadside UAS operation. The results showed that drivers do support the use of UAS specific TTC signs. Speed data from the driving simulator showed that a TTC configuration of two advanced signs caused drivers to decrease their speed by an average of more than $2\mathrm{km}/\mathrm{h}$ than when no TTC was present, while also inducing this deceleration at the most gradual rate.

A network adjustment program is an essential tool for surveyors. It allows the computation of point coordinates and confidence regions from measurements undertaken in the field. It also helps surveyors in the design of optimal networks, both in terms of accuracy and reliability. Conservatoire national des arts et métiers (Cnam), European Organization for Nuclear Research (CERN), and School of Management and Engineering Vaud (HEIG-VD) are three institutions that have developed their own network adjustment applications: Compensation de Mesures Topographiques (CoMeT), Logiciel Général de Compensation (LGC), and Trinet+, respectively. In all these applications, three-dimensional (3D) mathematical functional models are used to process conventional observations and global navigation satellite system (GNSS) 3D vectors. However, some discrepancies may exist in the obtained results between these applications due to differences in the implementation of the functional models. The main objective of this work is to study software effects, and to ensure compatibility and interoperability between these three network adjustment applications. We first present the relevant differences between these applications and then the processing methodology adopted to ensure the best compatibility and interoperability between them. Using generated measurements, which include Gaussian errors, we have been able to study the impact of any differences in the implementation of the functional models on the estimated variance factor and adjusted parameters.

Geometrical surveys are an important part of the renovation process in the oil and gas and shipbuilding industries. They enable improved safety and decreased costs of such types of processes. The crucial moment of such surveys is the determination of the position, deflections and dimensions of steel flanges in a local three-dimensional (3D) coordinate system. Companies that do such work declare submillimeter accuracy; however, no reliable publications have been found that could confirm this. This paper presents the main concept of such kinds of surveys and describes the two methods: standard and noncontact. The tests that were carried out allowed determination of the real measurement accuracy of flanges of different sizes for both methods. root mean square error (RMSE) was calculated for every parameter. The results show that for most of the flange parameters, the accuracy was better than 1 mm. The results indicate that the size of the flange and amount of measured points do not have a significant influence on the final accuracy; however, the distribution of the points is important.

Precise point positioning (PPP) employs readily available Global Navigation Satellite System (GNSS) orbit- and clock-correction products to perform point positioning using a single GNSS receiver. Recently, attention has turned to ambiguity-resolved real-time PPP (AR-RT-PPP), allowing PPP to potentially offer a viable alternative to real-time kinematic (RTK) positioning provided by local or regional Continuously Operating Reference Station (CORS) networks. Using an extensive data set covering all of New South Wales (NSW), Australia, this paper showed that AR-RT-PPP is achievable, on average providing positioning quality down to a few centimeters with an average ambiguity-resolution success rate of 84.3% and average convergence times of between 40 min and 1 h. The paper highlighted the advantages and disadvantages of this positioning technique from a user’s perspective and then outlined the current limitations and possible future direction of AR-RT-PPP as a fill-in service for sparser local or regional CORS networks.

Ambiguity dilution of precision (ADOP) and position dilution of precision (PDOP) are two popular scalar-diagnostics used in Global Navigation Satellite System (GNSS) positioning. Where the ADOP is a predictor for carrier-phase ambiguity resolution performance, the PDOP is meant to predict the receiver-satellite geometry’s capability for precise positioning. We will show, however, that although the PDOP works well for code-based positioning, one has to exercise great care in using the PDOP for real-time kinematic (RTK) positioning. We show that the ADOP and PDOP have distinct behaviors, an important consequence of which is that one can have time periods with small PDOPs, and thus seemingly good geometry for precise positioning, but at the same time large ADOPs, thus showing that successful ambiguity resolution and therefore precise positioning will not be possible. Also, the reverse situation may occur, i.e., having large PDOPs with small ADOPs. In such a situation, the large PDOPs should not automatically lead to the conclusion of poor position performance, because the large gain that ambiguity resolution brings will often still make precise positioning possible. We will analyze and explain this complementary behavior of the PDOP and ADOP and demonstrate this both analytically and empirically. For this analysis we use real Global Positioning System (GPS) single- and multifrequency signals and GPS/Quasi-Zenith Satellite System (QZSS), GPS/Navigation with Indian Constellation (NAVIC) L5 signals of two baselines located in Perth, Australia.

In precise point positioning (PPP) applications, uncalibrated phase delays (UPD) are applied to retrieve the ambiguity integers for achieving precise solutions over a short period. Also, the atmospheric corrections obtained from a dense reference network are applied to accomplish this task of shorter convergence time or even instantaneous ambiguity resolution. The combined BeiDou Navigation Satellite System (BDS) and Global Positioning System (GPS) PPP with regional network augmentation is presented with threefold contributions. First, in order to overcome the UPD-inherent unmodeled errors in undifferenced ambiguity resolution at reference stations, it is proposed to fix the single-differenced ambiguities and use them as a constraint to fix the undifferenced ambiguities. Second, the performance of combined $\mathrm{GPS}+\mathrm{BDS}$ PPP are fully evaluated with various indicators specified by single and combined satellite systems and several ratio test thresholds for ambiguity resolution. The BDS observations can provide the user with a significant improvement on the position solutions. The fix rate and correct fix rate are found to be increased by more than 7% and 11%, respectively. Third, the $\mathrm{GPS}+\mathrm{BDS}$ regional augmented PPP is assessed in a highly occluded urban canyon. The experiments show the unfix rates of the combined system are decreased by more than 40%, and the correct fix rates can be improved by up to 55% compared with a GPS-only scenario.

The Croatian Height Reference System for the epoch 1971.5 (HVRS71) is the official height reference system of the Republic of Croatia, newly established after Croatia’s independence. By using the network of the Second High Accuracy Leveling Network (IINVT) inherited from the former Yugoslavia after Croatia’s independence, which is the reference frame of HVRS71, several alternative realizations of the height reference system were performed. The alternatives are based on different realizations of height datums compared to the official Croatian Height Datum for the epoch 1971.5 (HVD71). Comparative analysis of the alternative height reference systems has been performed by comparing the absolute height accuracy criteria of the IINVT node benchmarks and the distribution of their height accuracy, i.e., by comparing the level of realized height positioning quality that the systems offer to the end users. The results show to what extent the concept of height reference system realization has an impact on the absolute height accuracy within the system using HVRS71 as a benchmark for comparison.

Technological advancements of the past decades have considerably changed the surveying profession and education required to become a surveyor. Many states require a combination of education (sometimes at least 4-year) and experience. There is an ongoing concern about the future of the profession, because the number of accredited schools is limited and enrollment often can be low. This is frequently connected with the low public awareness of the surveying profession. Therefore, it is important that surveying schools make efforts to increase the public profile of surveying. An important step towards this goal is to understand why and how students select surveying and their demographics. In addition, it is important to understand the opportunities and challenges of the local community. This study focused on the alumni and current students of Penn State University, Wilkes-Barre campus. A sample of 79 participants (45 alumni and 34 current students) was used. Occupation data and projections for surveyors in workforce development areas in Pennsylvania (and at the state level in neighboring states) highlight the areas that are and will be in need of surveyors in the future. Furthermore, this study considers high school enrollment, math scores from the scholastic assessment test (SAT), and population by race at the school district level. The survey results show that students are mostly white-male (81%). They enter the surveying field because they like to be outdoors, and they are interested in new technologies. They learn about surveying mostly from professionals (50%). However, only 50% stated that they knew about surveying in high school, which shows a concerning low awareness of the profession. The analysis with spatial data indicates low potential for recruiting in the vicinity of the Wilkes-Barre campus, and that recruitment and outreach efforts should focus in the southeastern, eastern, and western parts of the state.

The Great Wall bay has become an important investigation area due to the establishment of the Chinese Antarctic Great Wall scientific research station. Establishing a seamless chart datum and its transformation model with other vertical data is the key to unifying the sea–land measurement in vertical references. In view of this, two transformation models are constructed using two different realizations of the geodetic height of the mean sea surface (MSS), coupled with a seamless chart datum model of Lowest Astronomical Tide (LAT). One transformation model (Solution 1) forms MSS height by summing the modeled values of the Earth Gravitational Model 2008 (EGM2008) and averaged absolute dynamic topography based on gridded satellite altimetry products from January 2017 to April 2018. The other transformation model (Solution 2) utilizes the gridded MSS geodetic height product of DTU15, which was derived from multimission satellite altimetry from 1993 to 2015. The LAT seamless chart datum model was calculated based on the tidal constituents derived from the Atlantic Ocean 2008 model. The experiment area is located $-62.350°$ to $-62.100°\mathrm{S}$ and $-59.050°$ to $-58.600°\mathrm{W}$, which includes the entire Great Wall bay, and the accuracy of Solution 1 and Solution 2 have been assessed to be 12.0 and 11.2 cm according to the error propagation law. Then, compared with the field observation result by the pressure tidal gauge in the Great Wall bay, there exists in Solution 1 and Solution 2 differences of 127.6 and 42.2 cm, respectively. This shows that Solution 2 is much better than Solution 1, although it still far exceeds the accuracy evaluation of the solutions. The reasons for this has to do with the lengths of time of realized MSSs and the poor accuracy of satellite altimetry in the coastal waters.

Although maximum likelihood has been widely used to estimate unknown parameters in stochastic models of random errors, we show that the method cannot be used to estimate variance components for some stochastic models of routine measurement systems under some conditions, because the likelihood function is unbounded for such stochastic models. No optimal solution of variance components exists for these likelihood functions from the point of view of global optimization, implying that variance components for such stochastic models of practical importance cannot be estimated by maximizing the likelihood function.