Antonio T. Mozas-Calvache

Adapting 2D positional control methodologies based on linear elements to 3D

Abstract In this study we describe the adaptation of several 2D positional control methodologies based on linear elements to 3D. The selected methods have been used previously in several studies for controlling different kinds of lines and cartographic products, but always in a planimetric way. This study analyses the consequences of the inclusion of the heights in these methods by adapting the processes of calculation to the Z component. The methods to be adapted have been selected from the literature and are related to those based on calculations of distances and areas. The proposed methodology is applied to a real case, more concretely to a road extracted from two official databases in Spain, in order to check it and as a preliminary test for performing future 3D positional controls using these methods.

Accuracy of contour lines using 3D bands

This article describes a new methodology for the planimetric control of contour lines. The method is based on the generation of buffers around the contour lines which define a 3D buffer around the maximum slope line. After that we analyze the quantity of points from a more accurate source which is inside this buffer. As a result, we obtain a distribution function of the control points included when we apply several widths to the buffers. We have also determined the angularity and height differences of these points. The method has been applied to several sets of contour line intervals derived from a digital elevation model (DEM) and to the contour lines of one published topographic map using the DEM as the control source. We have also analyzed the representative behaviour of the contour lines, taking into account the contour line interval and the detection of an uncertainty model based on the slope variation. This study demonstrates the viability of the proposed method for obtaining the uncertainty of the contour lines depending on a given level of confidence and the variability of this uncertainty in the map. Finally, we propose a range of contour line intervals based on the scale and slopes.

Models for positional accuracy assessment of linear features: 2D and 3D cases

Traditionally, the uncertainty models for segments and lines and positional accuracy assessment methods based on lines have worked with 2D elements. But the increasing availability of 3D data leads us to conjecture the need to adapt existing models and methods for this type of data. This paper gathers for the first time in a single paper the uncertainty models for segments and lines and positional accuracy assessment methods based on lines, incorporating the 3D case. Thus, this paper is intended as a reference document for those readers who are interested in this field.

Detection of systematic displacements in spatial databases using linear elements

In this paper, we use control methodologies based on lines to detect the type of positional errors which affect a spatial database (SDB) and more concretely the presence of systematic errors. The methodology involves determination of the displacement vectors between the lines and a graphical and statistical study of the components obtained. The graphical analysis enables the detection of spatial patterns of displacement; the presence or absence of systematic errors is then confirmed by statistical analysis. We have applied this method to detect systematic errors on a set of lines with introduced displacements, rotations and scale changes. The results show the viability of the method. All the bias effects introduced were detected, both qualitatively and quantitatively. The detection method has the potential to minimize the effects of such displacements in the SDBs.

Analysis of behaviour of vehicles using VGI data

ABSTRACT This article describes a methodology for analysing the behaviour of vehicles on roads using data obtained from Volunteered Geographic Information and more specifically from GNSS traces. These data have a great potential for this goal due to their distribution, continuity and anonymity. The proposed methodology includes all possible stages, from traces selection and downloading, passing by filtering, matching and enrichment using official linestrings, to the final obtaining of results. The article also shows the main results obtained after applying this methodology to a real case that uses a large quantity of traces, distributed over a large zone of study, including several types of roads and conditions. These results allow us to analyse the behaviour of the implicated vehicles based on the speed and the acceleration or deceleration of each trackpoint which composes the traces and compare them with the general official data published by the traffic authorities. The analysis of the results has demonstrated the viability of this methodology and its possible implementation by traffic authorities in order to obtain information to improve traffic safety.

System for Evaluating Groups When Applying Project-Based Learning to Surveying Engineering Education

AbstractThis study describes the methodology developed for adapting project-based learning to the practice part of one subject of surveying engineering. The main innovation is the use of a system for evaluating the groups of students selected for the application of this methodology. This evaluation complements the one obtained from the project report developed by students, and it allows for individualizing the grade outcome of the members of the groups. For this purpose, the system takes into account the evaluations carried out by students of their own experience of teamwork. The system has been tested with several groups of students of surveying engineering. The results have demonstrated the efficiency of the system in showing and detecting the behavior of the groups, some problems appearing during the work, the involvement of students, and the sharing of tasks performed by some groups, among other issues. This experience can be applied to any other subject of engineering that contains a high level of pr...

Accuracy assessment of speed values calculated from GNSS tracks of roads obtained from VGI

This study describes the results of an assessment of the accuracy of relative measures between two points, and more specifically of speed values, obtained from Global Positioning Satellite Systems (GNSS) tracks acquired by contributors of Volunteered Geographic Information (VGI). The VGI does not usually include information about the positional accuracy of the trackpoints neither of speed values derived from these positions. Consequently, the assessment is based on a field test that consisted of a vehicle which travelled a highway with a set of Global Positioning System (GPS) devices like those commonly used by VGI contributors. These devices captured positions of trackpoints with a time interval of 1 second. Additionally, a more accurate geodetic RTK–GNSS receptor controlled these positions. The paper describes the methodology employed, taking into account several parameters such as the acquisition time interval, the accuracy of control positions, etc. The results have demonstrated the viability of the methodology applied, the possible use of VGI in order to determine the speed values of the trackpoints and the possible improvement in the accuracy achieved with the increase of the distance between trackpoints (and as a consequence of time interval), but with the disadvantage of a reduction in the quantity of trackpoints. Thus, several values of time intervals have been suggested, considering the accuracy required.

Web-Based System for the Self-Evaluation of the Calculations of Students Applied to Education in Surveying Engineering and Photogrammetry

In this paper, a Web-based system oriented toward students of surveying engineering and photogrammetry is presented. This application allows student self-evaluation of the calculations and problems involved in practical work. Students can evaluate their calculations before the final evaluation, minimizing the usual mistakes, primarily those of calculation errors. The evaluation of this system is based on the numbers and types of access to the system; the results of a satisfaction survey; and, primarily, a test of the proposed learning methodology. These results have demonstrated the viability of the tool developed in this project with regard to achieving the main objective, which consists of the students’ self-evaluation of their calculations and assimilation of the causes of their mistakes. The system is therefore shown to reinforce and stimulate autonomous learning.