ABSTRACT Considering the importance of topographic surveys to determine soil volumes and study efficient and accessible alternatives for this operation, this study aimed to analyze methods and ...respective equipment for planialtimetric surveys to determine soil volume. An experimental grid was installed in an area locate in Fernandópolis, SP, Brazil, in which quotas were measured by geometric leveling (standard method), trigonometric leveling, leveling with receivers of the Global Navigation Satellite System (GNSS) by relative (frequencies L1/L2) and absolute positioning (code C/A) and extraction of altitudes in digital terrain model from SRTM and ASTER images. In comparison to geometric leveling, trigonometric leveling was the most accurate in determining soil volume (0.6% error), followed by GNSS leveling by relative positioning (23.7% error), and extraction of altitudes by SRTM (32.0% error) and ASTER images (38.3% error). GNSS leveling by absolute positioning presented the highest error in determining soil volume (287.4%) compared to the other methods.
Details regarding the public safety of engineering structures can be gleaned from measurements and monitoring. The development of a methodology for monitoring and analyzing structures' vertical ...displacement is explained in this paper. The developed methodology aims to add a new dimension to geometric leveling, and leveling routing, by applying a least squares solution for level network adjustment and performing statistical analysis to assess the change in vertical displacement. To monitor and analyze the vertical deformation of a building in Cairo, Egypt, the proposed methodology was utilized. Twenty monitoring points, five auxiliary points, and three local reference stations were utilized. All the measurements were taken with a geodetic invar staff and an automatic level with an attachment of a parallel plate micrometer. The observations were made for an interval of 81 months. The least squares adjustment technique was applied to obtain the adjusted levels and observations and to generate the required statistical data. The results of the subsequent epochs were compared to the results of the first epoch to determine the vertical movement of the monitoring points for each epoch. In addition, the significance of the present displacement was ascertained by comparing the values of vertical displacement to the determined 95% corresponding confidence intervals. The findings demonstrated that the building remained stable throughout the monitoring period. The case study demonstrates how effectively geometric leveling with least square adjustment can be used to monitor the vertical displacement of structures.
The city of Recife, in the northeast of Brazil, is formed by a coastal plain, which is surrounded by several hills, the Atlantic ocean and a number of rivers that cross the city. The plain was formed ...by fluviomarine sediment, which was produced by marine transgressions and regressions. Its hydrogeological characteristics and geographical position, located slightly above sea level, lead to water-related problems, such as coastal erosion and frequent flooding. In the last 50 years, an increase in the exploitation of groundwater has caused a lowering of the piezometric surface (up to 100 m at certain points). In porous sedimentary aquifers, pumping fluid decreases pore pressure and reduces the support provided by the overlying layers of soil. This reduction in pressure is caused by the lowering of the piezometric surface and leads to soil deformation, usually called subsidence. As a result of the excessive exploitation of groundwater in Recife, and the consequent decrease in groundwater levels, soil subsidence has become a great concern and requires careful investigation. Geodesic methods of monitoring and quantifying the vertical deformation of soil, caused by the removal of groundwater, have been used around the world. The present study describes a method of assessing the occurrence of soil subsidence in an area where excessive exploitation of groundwater has taken place. High-precision geometric leveling was used to quantify the phenomenon and to perform comparative analysis of altitude values from the year 1958 with more recent altitude values (from 2012 and 2015). The experiments confirmed a difference of 3.86 cm for one of the reference levels, located within the subsidence monitoring area. Thus, the leveling analysis provided estimates of a vertical displacement of approximately 0.68 mm/year in this area.
To assess the accuracy of vertical components obtained by Classical RTK and Network Real Time Kinematic positioning with different correction methods with setting of different number of epoch, height ...differences obtained from precise geometric leveling was used as reference height differences along with those obtained from static GPS only solutions, and combined solutions of GPS and GLONASS on different GNSS days. One-way variance analysis (ANOVA) were applied to the height differences to test them whether they are significantly different or not. The significant differences, if any, were further tested by using Post Hoc test to reveal the effects of the method used, the epoch number, or the measuring time, which is responsible for the significant differences. The results from ANOVA showed that the number of epoch had not much effect on the vertical components but on the correction methods. MAC method presented the most deviated results compared to the other methods with different GNSS days’ solutions. In general, VRS method was found to be the most consistent method among others used. This study is important in both; an accuracy assessment with respect to the most precise method in heights (i.e., precise geometric leveling) was carried. The techniques (ANOVA and Post Hock Test) used in the accuracy assessment.
Between August 2016 and January 2017, a very energetic seismic sequence induced substantial horizontal and vertical ground displacements in the Central Italian Apennines. After this event, the ...Italian Military Geographical Institute (IGM), owner and manager of the Italian geodetic networks, executed several topographic surveys in the earthquake area in order to update the coordinates of vertices belonging to the IGM95 geodetic network. The measurements began in the areas where the most significant deformation occurred: the localities of Amatrice and Accumoli, in the Rieti Province, and the area covering Norcia and Castelluccio, in the Province of Perugia, all the way to Visso (Province of Macerata). The activities described in this paper focused on the updated measurement of the IGM95 network points through GNSS and the restatement of extensive parts of the high precision geometric lines that were levelled until reaching stable zones. This unprecedented amount of data was used for a new geological interpretation of the seismic sequence, which confirms some of the previous hypotheses of the scientific community. In the analyzed territory, the latest estimate of the geodetic position points has allowed for an accurate determination of the east and the north and of the altitude components of the displacement induced by the earthquake through a comparison with the previous coordinates. The results confirm that the seismicity was induced by normal faults system activity. Still, they also indicate the possible influence of a significant regional thrust that conditioned the propagation of the seismicity in the area. The obtained maps of the displacement are coherent with other geodetic works and with a rupture propagation driven by the documented geotectonic structure.
The authors study the ground surface displacement in the area of Zhezkazgan copper ore field now subjected to extraction of ore reserves from rib pillars. The high-precision leveling procedure using ...digital leveling instrumentation and invar leveling staffs is proposed for the application in arrangement of a geodynamic test site at the settlements of Zhezkazgan and Lermontovo. The steel control survey points are firmly connected with rock mass by means of grouting. The observation results made it possible to detect and evaluate the ground surface displacements.
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