Applied Geomatics最新文献

A visual inspection, which entails field surveying, such as photodocumentation and footage, is the first step of a multi-level approach to bridge health assessment. Furthermore, the use of surface models, CAD drawings, and orthophotos, guarantees complete and accurate documentation, thus allowing for a better understanding of the environment, the anthropic structures, and their relationships. All the georeferenced surveys’ outputs are especially advisable within a prespective of periodical monitoring, as forseen by national legislation. The work is aimed to study two adjacent bridges over the Arno River in Lastra a Signa, Italy. One of the bridges, Ponte nuovo sull’Arno, is an overpass for motor vehicles. The other one, which is called Passarella sull’Arno, is a pedestrian viaduct. A topographic reference network has been settled using the GNSS survey technique. 3D point clouds of the bridges have been acquired by performing a Laser Scanning survey. A bathymetric survey has been carried out to acquire a 3D point cloud of submerged bridges’ parts and the riverbed. Through a Photogrammetric survey from RPAS, an orthophoto of the area has been built. Finally, evidence of historical submerged bridge structures has been identified thanks to the multi beam survey. The work’s objective is to integrate surveying geomatics techniques to create a reliable survey of the bridges, the surrounding area, and the riverbed, as support to the most common structural health assessment methods.

In 2015, the International Association of Geodesy published a resolution on the International Height Reference System definition. It is defined that the vertical coordinate must be given in geopotential number and that the realization of this system must be done considering gravity values arranged homogeneously around the stations. However, it should be regarded that for the stations that are located on the coast. This fact can cause a loss in accuracy in determining the potential gravity. Until now, the studies consider only global gravity models, coming from satellite gravity missions to complement the data in the oceanic region and not considering high-frequency components of the gravity field measured at the surface. Consequently, this research considered shipboard-measured marine gravity data integrated with global marine gravity model data derived from altimetric satellites (DTU17 and GRAV31.1) to compute the gravity potential for the two coastal stations that are part of the International Height Reference Frame (IHRF) in Brazil, CEFT and IMBT stations. The gravity potential was computed following the standardization determinations for the IHRF, and the results showed that the marine gravity data incorporated into the computation did not contribute to accuracy.

Abstract

The paper considers the combined adjustment problem both of GNSS and geotechnical sensor (slit meter) measurements to detect the deformations at large engineering structures. The study offers mathematical apparatus and formulates the basic restrictions for combined processing of geodetic and geotechnical data. A preliminary assessment indicates a significant improvement in the displacement detection accuracy (up to 1 mm in planar and vertical direction). The approbation of the proposed method was performed using time series of measurements of GNSS receivers and slit meters located on the Dniester hydroelectric power plant (HPP) dam for the period from 2017 to 2019. Gross errors were excluded before processing from all the time series of observations in the semi-automatic mode using a specially designed filter. Additionally, the high-frequency noise was removed by low-pass filter (period 0.2 years). The analysis of obtained adjustment results proved the effectiveness of the proposed method. However, a number of shortcomings were identified, related to non-compliance with the main restrictions: systematic errors in the input data, lack of strict parallelism of slit meters axis to the coordinates axis of local reference system, and violation of monolithic conditions of separate blocks of the objects where slit meters are installed.

Co-registration is required when the alignment of two or more point clouds obtained for mapping natural and built environments is needed. While closed-form solutions are suitable for co-registration, most of the existing approaches rely on unit quaternion solutions for the estimation of transformation parameters from point or plane correspondences. This paper presents a novel co-registration of terrestrial light detection and ranging point clouds solution to create globally consistent 3-D environments. Our method exploits the advantages of the dual quaternion solution combining both points and plane correspondences. The role of our relaxation labeling technique in 3-D matching (3PRL) is investigated, and its efficiency to find the best plane correspondences is shown. The paper also presents a method to treat degenerate plane configurations with corresponding virtual points. Experimental results reveal that our 3PRL technique can update and improve the 3-D matching probabilities using binary relations. At the same time, the proposed dual quaternions point- and plane-based optimization indicated that the mathematical optimization might represent a valid model for co-registration of point clouds. A closer inspection of co-registration accuracy revealed that the translation and rotation error mean decreased drastically, with margins between 0.10 m and 0.17 m and 0.01° and 0.33°, respectively. Experiments have shown that our method generally achieves better results than existing methods.

Abstract