Abstract
Abstract Currently, in Brazil, for the assessment of the Positional Accuracy of non-point features (lines and polygons), there is no standard norm of execution. This work aims to compare the results of two methodologies that allow determining the average value of the discrepancies between linear features. The first, Equivalent Rectangle Method, aims to determine the discrepancy by considering an equivalent rectangle for the polygon obtained from the two homologous lines. The second, Double Buffer Method applies a buffer on both lines and obtains the average discrepancy value based on the relation of the areas of the generated polygons. These methods were compared in two steps. Initially, an experiment was performed with features of known measurements, where the displacement of the homologous lines was controlled in azimuth and distance. In this step, it was verified that the shape of the feature and the direction of the displacement interfere in the results of both methods when compared to the traditional procedure of measurement of discrepancies by homologous points. In the second stage, we evaluated the vector data of the OpenStreetMap (class of roads), with reference to a more accurate vector dataset produced for the Mapping of the State of Bahia. As a result, for the 1:25,000, 1:50,000, 1:100,000 and 1:250,000 scales, it was obtained, respectively, the PEC-PCD for the Equivalent Rectangle Method "C", "B", "A" and "A" and the PEC-PCD for the Double Buffer Method "R", "C", "B" and "A", where "R" means that it has not achieved the minimum PEC-PCD classification.
Highlights
In the last years, the cartography has received the voluntary and non-commercial contribution of several institutions for global mapping, a phenomenon known as Volunteered Geographic Information (VGI) (Goodchild, 2007)
The objective of this procedure is to investigate the results of the Equivalent Rectangle Method (ERM) and Double Buffer Method (DBM) applied to features with different shapes and different types of displacements, given a certain distance, for homologous pairs of lines
In order to obtain different configurations of the pairs of homologous lines and eliminating some symmetrical relative positions, the azimuths shown in Figure 6 were considered, where the test lines are dashed in red and the reference lines are in black color
Summary
The cartography has received the voluntary and non-commercial contribution of several institutions for global mapping, a phenomenon known as Volunteered Geographic Information (VGI) (Goodchild, 2007). In this context, it stands out the OpenStreetMap (OSM) (Sehra et al, 2014). For paper topographic charts (known as analogical products) produced officially in Brazil for systematic mapping, the positional accuracy follows the Cartographic Accuracy Standard (Padrão de Exatidão Catográfica - PEC) which parameter values were established in Decree No 89.817 of June 20, 1984 (Brazil, 1984), transcribed through the Table 1. With the recent evolution of digital cartography and the geotechnology's resources, new products require other quality parameters, including a refinement of the positional accuracy assessment (Ariza-López et al, 2007) and computational programs to perform it (Nero et al, 2017)
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