Topographic Survey and Modelling using Photogrammetry: A Comparison against Electronic Distance Measurement (EDM) Method

Topographic surveying has been an important companion to the civil engineer in the development of human civilization since ancient history. It is used to map terrestrial features on the ground along with its contour heights. Application of this can be seen in the establishing land boundaries and setting out construction projects. Conventional methods of surveying range from ground field methods such as the use of total station to aerial surveys such as photogrammetry or LiDAR. This study looks to assess the feasibility of aerial photogrammetry using UAVs as a replacement to the conventional EDM survey using total stations. This objective was achieved by carrying out both photogrammetric and EDM surveys on a 350m long stretch of highway. The resulting survey data were processed to produce two comparative TIN surfaces of the highway which were then superimposed together and compared for accuracy. It could be observed that on plan view, both surfaces were quite closely matched with a maximum difference of less than 0.4m and a low standard deviation. In elevation view, however, the differences were larger with maximums of 5.0m, accompanied by large standard deviations. RMS error analysis carried out also correlate with the findings.

Modelling the Soufrière Hills Volcano; Investigating the Montserrat magmatic system with co-analysis of EDM and GPS data

<p>Ground deformation offers vital insight into the activity of volcanoes, as well as the characteristics of the magmatic systems that feed them. The extended eruption of the Soufrière Hills Volcano (SHV) has allowed for the development of a comprehensive multi-disciplinary monitoring network, which has aided extensive research into the magmatic system underlying the volcano. The modern network comprises GPS, strainmeters, and cheaper Electronic Distance Measurement (EDM). However, the island’s EDM network has to date only being used for monitoring the SHV. Here, for the first time, we co-analyse the EDM dataset from 2010-19 with the GPS data from the same period. This study aims to delineate the modern magmatic system conditions by building 3D Finite Element Models, as well as assessing the best use of EDM data in modelling the SHV.</p><p>The island-wide deformation recorded over the past decade at the GPS network is broadly radial relative to the SHV dome, with a decreasing deformation rate. The EDM data shows line lengthening on the west and east flanks of the volcano, but minor line length shortening on the northern flank. We utilise Finite Element Modelling to model the SHV magmatic system as a single elongated prolate with 3D topography incorporated. We systematically test a wide range of parameters to explore how both EDM and GPS record perturbations to the magmatic system. Our preliminary results show that variations of certain parameters to the deeper magmatic system have an impact on both EDM and GPS timeseries, while some parameters (e.g., source pressure, source depth, and source location) have a more significant effect on EDM measurements than others (e.g., source shape).</p>

Past, Present and Future Monitoring at the Vallcebre Landslide (Eastern Pyrenees, Spain)

Works carried out to monitor the displacements of the Vallcebre landslide (Pyrenees range, NE of Spain) since 1987 are presented. The landslide, which extends over an area of about 0.8 km2 and affects more than 20 × 106 m3, has experienced displacements of up to one meter per year in some points and periods. It has been periodically monitored since 1987, using a wide range of surface and in-hole techniques: triangulation with theodolite, Terrestrial Photogrammetry, Electronic Distance Measurement, GNSS-GPS, inclinometers, wire extensometers, piezometers, DInSAR (satellite) and GBSAR (terrestrial). The results obtained using new techniques are compared with those obtained with GNSS-GPS and a wire extensometer, and checked against fixed stable points. From this comparison, we conclude that even though wire extensometers and inclinometers may have the highest precision, in practice, all systems play potentially valuable roles in providing meaningful data for monitoring at different study stages. In the near future, we envisage the installation of a Distributed Fiber Optic array to monitor the risk with a certain space and time continuity. After the evaluation of the precision and advantages of the different methods, the complementary use of some of them is strongly recommended.

On the application of nature-inspired grey wolf optimizer algorithm in geodesy

Nowadays, solving hard optimization problems using metaheuristic algorithms has attracted bountiful attention. Generally, these algorithms are inspired by natural metaphors. A novel metaheuristic algorithm, namely Grey Wolf Optimization (GWO), might be applied in the solution of geodetic optimization problems. The GWO algorithm is based on the intelligent behaviors of grey wolves and a population based stochastic optimization method. One great advantage of GWO is that there are fewer control parameters to adjust. The algorithm mimics the leadership hierarchy and hunting mechanism of grey wolves in nature. In the present paper, the GWO algorithm is applied in the calibration of an Electronic Distance Measurement (EDM) instrument using the Least Squares (LS) principle for the first time. Furthermore, a robust parameter estimator called the Least Trimmed Absolute Value (LTAV) is applied to a leveling network for the first time. The GWO algorithm is used as a computing tool in the implementation of robust estimation. The results obtained by GWO are compared with the results of the ordinary LS method. The results reveal that the use of GWO may provide efficient results compared to the classical approach.

Overview of Merapi Volcanic Activities from Monitoring Data 1992–2011 Periods

Merapi, the dangerous active volcano in Indonesia, has been monitored since the 1920s by applying several methods and tools. The monitoring data from earlier times are stored well and can be used as reference for any precursors and signs before each eruption. This article evaluates the long-term activity of Merapi from the monitoring data for 1992–2011 to obtain the trends and patterns before the eruption period by combining the seismicity, deformation, volcanic gas, and temperature data in the same time span. Several characteristics are exhibited before effusive and explosive eruptions, i.e., a significant level up in volcano-tectonic energy and increased CO2gas concentration indicating an explosive eruption. Effusive eruption is characterized by a significant multiphase earthquake with less occurrence of deep and shallow volcano-tectonic events. Deformation data from a tiltmeter and electronic distance measurement are important in understanding the dynamics of the lava dome and the eruption direction.

The Possibility of Using Navigation GPS Devices in the Survey Engineering

As a result of the tremendous development in the field of computer technologies, communications and information revolution, new applications which has seen a tremendous development in terms of devices and technologies used in various applications such as a device Electronic Distance Measurement (EDM), Total Station, GPS (Surveyor and Navigational)… etc. In this study, five-ground control points (BM) were made to provide traverse, and these points observed by using three different navigation GPS devices, and observed by using TOTALSTATION device, and using spatial and statistical analysis functions in GIS. The study showed that the error in these devices is a random error varies from one device to another. In addition, it showed that the error varies from time to time. Cannot be determined the spread of readings to the observed point (by navigation GPS) in a particular direction or specific frame, as well as the central distance of the readings are changing from one device to another and from point to point.The study recommends that should not be used navigation GPS devices in the survey work. In addition, re-survey all areas are observed or defined its borders by using this device (navigation GPS) by serving GPS devices with the required accuracy.

Twenty Years of Experience Running Calibration Baseline

The authors of the paper are sharing their 20 years of experience in using Kyviškės Calibration Baseline. The Kyviškės Calibration Baseline (1320 m) is the longest calibration baseline in Lithuania. The baseline is calibrated regularly with 5–7 years period. The first time these measurements were performed in 1997 and repeated in 2001, 2007, 2008 and 2014. The same Kern Mekometer ME5000 EDM (electronic distance measurement) instrument was used for all the measurements performed. By building additional pillar aside from the baseline pillars the Kyvišk2s Baseline was converted to a triangle-shaped test field in 2000. The results confirm good stability of the baseline, which is now used for calibration of the EDM instruments, total stations and GNSS (global navigation satellite system) receivers.

Influence of surface reflectivity on reflectorless electronic distance measurement and terrestrial laser scanning

The uncertainty of electronic distance measurement to surfaces rather than to dedicated precisionre flectors (reflectorless EDM) is afected by the entire system comprising instrument, atmosphere and surface. The impact of the latter is significant for applications like geodetic monitoring, high-precision surface modelling or laser scanner self-calibration. Nevertheless, it has not yet received sufficient attention and is not well understood. We have carried out an experimental investigation of the impact of surface reflectivity on the distance measurements of a terrestrial laser scanner. The investigation helps to clarify (i)whether variations of reflectivity cause systematic deviations of reflectorless EDM, and (ii) if so, whether it is possible and worth modelling these deviations. The results show that differences in reflectivity may actually cause systematic deviations of a few mm with diffusely re- flecting surfaces and even more with directionally reflecting ones. Using abivariate quadratic polynomial we were able to approximate these deviations as a function of measured distance and measured signal strength alone. Using this approximation to predict corrections, the deviations of the measurements could be reduced by about 70% in our experiment.We conclude that there is a systematic effect of surface reflectivity (or equivalently received signal strength) on the distance measurement and that it is possible to model and predict this effect. Integration into laser scanner calibration models may be beneficial for high precision applications. The results may apply to a broad range of instruments, not only to the specific laser scanner used herein.