Journal of Surveying Engineering

This paper presents two new solutions for transition curves that make it possible to create a smooth connection between two arbitrarily located points. For this reason, the curves are referred to as universal transition curves. The solutions are based on Degree 4 and 5 polynomials and describe the entire curved transition between the set points using only a single equation. The paper also describes a procedure for designing an arc with the use of these curves. The design process requires exact information concerning the location of the two points to be joined (i.e., $P$ and $K$) as well as the directions of the tangents at these points together with the curvature radii at $P$ and $K$. Such a data set is necessary owing to the form of the equations describing the universal transition curves. The design principles have been illustrated with relevant numerical examples.

The calibration and accuracy analysis of a novel, low-cost, adaptable mobile laser scanning (MLS) system using a Velodyne HDL-32E laser scanner and an Oxford Technical Solutions Inertial+2 inertial navigation system, is described. First, a static calibration of the laser scanner is discussed. The static calibration is shown to improve the overall relative accuracy of point cloud data from the scanner by approximately 20% over the manufacturer-supplied calibration. Then, the determination of system boresight angles and lever-arm offsets using a planar patch least-squares approach is presented. Finally, the calibrated and boresighted MLS is operated in a backpack mode to acquire multiple data sets in an area that contains dense ground control acquired using static terrestrial laser scanning (TLS) and a high-end, survey-grade MLS. The dense ground control is used to examine several methods of estimating the overall errors of the backpack MLS system. Detailed comparison of the MLS data with the TLS and survey-grade MLS control shows that, despite the system’s low cost, it is able to reliably collect point cloud data with greater than 10-cm three-dimensional root-mean-square error accuracy.

This work is part of the European Organization for Nuclear Research (CERN) Neutrinos to Gran Sasso (CNGS) Project, aimed at estimating the velocity of neutrino beams directed from CERN in Geneva toward the Gran Sasso National Laboratory (LNGS) in Assergi, Italy. In particular, the distance has to be estimated between the Large Volume Detector, Icarus, and Borexino reference points, located inside LNGS, and the CERN laboratory target. All the points at LNGS and CERN are placed in underground laboratories. Traditional surveying methods must then be applied for connecting the reference points to benchmarks established outside the underground laboratories in the open field. In this way, the two local LNGS and CERN geodetic networks can be connected by the Global Navigation Satellite System (GNSS) technique. The CERN target was already estimated with respect to a local GNSS network in the International Terrestrial Reference Frame 97. To estimate the position of LNGS points, a new local GNSS network has been materialized. This network integrates with an underground topographic network that connects the reference points in the laboratories. The distance between CERN and LNGS is approximately 730 km, and the required accuracy is better than 0.1 m. Therefore, GNSS processing and underground surveys must be performed according to high-precision standards. This paper describes the performed operations and the obtained results.

Curves represent the most interesting element to be analyzed when evaluating the operational and safety effects of road geometrics. Despite the existence of several static and dynamic survey techniques, the correct identification of curves and the interpretation of spatial data from horizontal road alignment surveys still present a challenge. This paper presents the results of an investigation into the effects of both accuracy and sampling frequency (i.e., the interval between data points) of alignment spatial data on the identification of the radius and center of curvature. In pursuit of this objective, the authors adopted an original approach consisting of the generation of dispersed spatial data points from circular arcs with known characteristics. The least-squares, Huber, and Landau methods were used to back-calculate the radius and the coordinates of the center of curvature and to assess the effects of accuracy and interval between data points. The results obtained quantified the effects of accuracy, interval between points, radius magnitude, and length of circular arc on the identification of circular arcs. In support of future survey activities, considerations regarding the accuracy of measurements, the sampling frequency, and arc characteristics (i.e., length, radius) are discussed in the paper.

This paper documents measured deformation within four global positioning system (GPS) networks deployed on critical, heavy-engineered infrastructure in real time over a combined 5-year period. The first is an ∼2-km, four-lane floating freeway that deforms daily in response to temperature and traffic loads and seasonal lake-level variation. The second is a 6-lane elevated freeway ∼1 km in length that has subsided unevenly and discontinuously since it was damaged by the 2001 (M_W 6.8) Nisqually earthquake. Two additional structures comprise ∼300-m-long, earth-filled dams forming major reservoirs (Howard A. Hanson and Tolt dams). Real-time kinematic processing of high rate (1s or 5-s epochs) GPS observations over short baselines (0.1 to ∼1 km) permits continuous deformation monitoring at centimeter-level accuracy, whereas long-term deformation was measured at subcentimeter accuracy through postprocessing of 24-h observations. The floating freeway showed 60 cm of annual vertical displacement and a 1.4-± 0.4-cm short-period oscillation that correlates with traffic and temperature but no response to bridge-perpendicular winds gusting to 74 km/h (40 knots). Along the elevated freeway, 4–7 mm/year of lateral displacement and 4.3 ± 14 mm/year of subsidence is observed. At Howard A. Hanson Dam, daily measurements show a slow response at the southernmost portion of the dam to the filling with water of a 30-m-deep pit excavated adjacent to the dam. The fourth structure, Tolt Dam, is stable but shows a vertical response to reservoir level and appears to isolate its GPS receivers from a well-documented regional hydrological signal.

This paper presents an estimation method allowing direct and robust outlier assessment of parameter shifts in functional models of geodetic observations. The systems adopted in the discussion refer to functional models used in geodetic network deformation analysis. The proposed method is a robustness-oriented development of $\text{Shift}-{\mathrm{M}}_{\text{split}}$ estimation. The problem of robustness is solved using an additional random variable with realizations that are outliers. The paper shows that the application of this variable also facilitates the selection of the appropriate number of competitive models in ${\mathrm{M}}_{\text{split}\left(q\right)}$ estimation. Two numerical examples explain the manner of $\text{Shift}-{\mathrm{M}}_{\text{split}}^{\ast }$ estimation performance and indicate the basic properties of the determined estimates.

This paper offers a new method for mapping as-built tunnels excavated by tunnel-boring machines (TBMs) that is conveniently applicable and cost-effective. The presented procedure can algorithmically be explained as follows: (1) surveying some points on the edge of each segment using a reflectorless total station in an arbitrarily initial coordinate system, (2) shifting the measured coordinates to a location as close as the origin of the initial frame, (3) fitting a plane to the shifted coordinates of the measuring points, (4) deriving the direction angles between the normal vector and the axes of the coordinate system, (5) rotating the shifted coordinates around the third and first axes of the frame, (6) fitting a circle to the transformed coordinates to determine the position of its origin, and (7) transforming the derived coordinates of the circle origin into the initial coordinate system. The capability and reliability of the method have been indicated by means of simulated data sets. The method has also been applied to the survey measurements in excavating Line 7 of the Tehran metro network by TBM. The results affirm the proficiency of the proposed method to scan as-built tunnels.

The detection of multiple outliers can be interpreted as a model selection problem. Models that can be selected are the null model, which indicates an outlier free set of observations, or a class of alternative models, which contain a set of additional bias parameters. A common way to select the right model is by using a statistical hypothesis test. In geodesy data snooping is most popular. Another approach arises from information theory. Here, the Akaike information criterion (AIC) is used to select an appropriate model for a given set of observations. The AIC is based on the Kullback-Leibler divergence, which describes the discrepancy between the model candidates. Both approaches are discussed and applied to test problems: the fitting of a straight line and a geodetic network. Some relationships between data snooping and information criteria are discussed. When compared, it turns out that the information criteria approach is more simple and elegant. Along with AIC there are many alternative information criteria for selecting different outliers, and it is not clear which one is optimal.

The optimal configuration of a resection network plays an important role in the precision analysis of free stations. The two conditions of the optimal configuration for distance-only resection networks were derived. Based on the two conditions, the regular sector configuration was proposed, and the character of the optimal configuration was determined. Furthermore, the geometric dilution of precision (GDOP) for a generic direction resection network with n known points was deduced. The conclusion was reached that A-D-E-optimality cannot be simultaneously achieved in the direction resection network. The pursuit of only the lowest GDOP is impractical in engineering, whereas the E-optimality criterion is suitable in such a situation, as shown by cases with three known points. There are typically two E-optimal configurations for a three-known-point direction resection network, and the regular pattern was explored. Finally, the configuration of a heterogeneous resection network was analyzed. An in-depth understanding of the resection network configuration is provided, which is beneficial for developing an initial guess for the optimal resection network configuration in practice.

Monitoring of measurements needs to be supported by a thorough knowledge of the achievable accuracy of the measurement equipment and the processing methodology. This study on ovalization monitoring with laser scanning in tunnels under construction focused on fast-performing laser scanners and their achievable accuracy. This research also investigated the optimum smoothing level of the laser scanning data to achieve the best estimates of ovalization. The experimentally based standard deviations indicate that the used phase-based laser scanner delivers highly accurate results with standard deviations between 0.34 and 0.58 mm, depending on the applied smoothing level. In this research, this laser scanner was used, together with a [x – 0.008 rad; x + 0.008 rad] smoothing interval on the calculated radius values to meet the accuracy requirement requested by the client (0.5 mm), even when using multiple setups. Another used type of laser scanner (pulse-based) also delivers standard deviations around this range, but this instrument has a lower scanning speed and a smaller vertical field of view, making it less adapted for measurements in time-restricted tunnel-monitoring projects.

Implementation of spatial data infrastructures (SDIs) can maximize access to geographic information (GI) and, through geoportals or other access points, serve as a powerful tool in different fields of practice and specialization. In many countries, the most important sources of infrastructure reference data are survey databases and land information systems managed by surveying and mapping services. However, the SDI frequently has a more interdisciplinary character, which influences the value derived from its use by different communities. This paper aims to present the evaluation criteria of SDI usefulness and usability in the implementation of certain land-surveying tasks. The case study focuses on the Polish SDI (PSDI) and its main access point, Geoportal 2. SDI evaluation considers information and support provided by Geoportal 2, as well as the infrastructure’s impact on use process and user organizational performance. Surveyors consider the PSDI a resource for information from geodetic and cartographic service centers and from previous field reconnaissance.

The Online Positioning User Service (OPUS) operated by the National Geodetic Survey (NGS) has consolidated into a very attractive tool for surveyors, engineers, and the academic community to procure precise/accurate positions from global positioning system (GPS) observations. The OPUS utility continues to be improved since it was successfully launched in 2000. In general, each update results in better reliability of the precision and accuracy of OPUS solutions. However, necessary software modifications could also introduce certain biases, some significant, complicating the interpretation of OPUS results, particularly for applications that rely on high-accuracy absolute positions. This article concentrates on the interpretation of OPUS-Static solution reports primarily in relation to the transformation of reference frames and geoid models, which are two basic scientific ingredients in practical geodetic-surveying enterprises. One-year continuous GPS observations collected at a landslide site in Puerto Rico were uploaded to OPUS-Static on April 20, 2011; October 30, 2013; and April 29, 2015. The OPUS solutions obtained at these three dates were compared. This case study indicates that very considerable changes in orthometric height and horizontal coordinates could occur among OPUS outputs processed at different dates. OPUS users who focus on absolute positional coordinates should pay special attention to the periodic updating of reference frames and geoid models by NGS.

The concept of global navigation satellite system (GNSS) real-time kinematic (RTK) positioning through the use of multiple reference stations (Network RTK) is the most common approach to relative positioning, which makes it possible to achieve centimeter-level accuracy for medium baselines. In this approach, ionospheric and geometric correction terms, generated on the basis of a model of interpolation of the distance-dependent biases, are applied to the functional model of rover positioning. The accuracy and reliability of Network RTK performance depend on the accuracy of the defined correction terms. Especially during storm-level ionospheric activity, the applied spatial interpolation model might not be suitable for the real ionospheric state, causing the ambiguity resolution to be less reliable, or even impossible, because of high residual errors. Thus, the residual errors can substantially degrade the correctness of the functional model and should be accounted for to obtain optimal estimation of the unknowns in the positioning model. One of the possible approaches for taking into account such errors is to introduce them into a stochastic model rather than a functional model. This paper provides a method of taking into account residual errors in the stochastic description of the positioning model by using the accuracy characteristics of the correction terms directly defined in the network solution. It describes a method of developing the proposed stochastic model (called the Network-Based Stochastic Model), including of the test results of the instantaneous Network RTK positioning performance.

Recent techniques for acquiring elevation, such as the advanced synthetic aperture radar (SAR) interferometric techniques, enable the creation of very detailed models in a short time. However, because of its incapacity to penetrate the water, the collection of bathymetric information in water-covered areas must be performed with other techniques. Thus, data compatibility is a key factor for two-dimensional (2D) hydrodynamic simulations because a single elevation model is required in general. Such operation is often challenging, because it is not simply obtainable by merging the data sets or replacing the main river channel information with the bathymetry. This study presents a geographic information system (GIS)–based methodology to merge the bathymetry and topography of a river and validates it with 2D flood event simulations. Therefore, the floodplain topography data sets, including emerged fluvial features and profile-shaped bathymetric surveys covering only limited sections of the river channel, were combined to produce a single elevation model. The methodology is based on the extraction of the riverbanks on a digital elevation model (DEM) to locate the thalweg and two ancillary lines, which support an interpolation of cross-section data. The case study is the middle section of the Tagus River in Portugal, for which distinct data sets of bathymetry (namely, cross sections) and a DEM obtained by the advanced interferometric techniques were available. A segment of flooded/unflooded areas obtained from a SAR image of a previous flood event was used as a basis to compare the flooded area resulting from two hydrodynamic simulations. The disagreement in flooded area extension was reduced from 12% difference to 1% using the proposed combined DEM. Water levels, measured at a hydrometric station, were also used for assessment. A significant improvement was also found using the combined DEM: the maximum water level differences decreased from 218.7 to 24.4 cm.

It is increasingly popular in surveying to accommodate the grid/ground distance difference associated with map projections by adopting what is called a low-distortion projection (LDP) for a specific area. The advantage is that the LDP distance between a pair of plane coordinates will match the horizontal ground distance within a predetermined tolerance. With a tolerance limit in hand, design parameters for a LDP need to accommodate a range of elevation in the area while maximizing the geographical area to be covered. Typical LDP applications include a city, a county, or some other specified area. Regardless of whether using an existing state plane coordinate (SPC) map projection or a LDP, the combined factor reflects the distance distortion for a line and can be defined as the ratio of the grid inverse distance divided by the corresponding horizontal ground distance. This article describes use of the global spatial data model (GSDM) to compute a closed-form combined factor for a given line.