Avaliação da acurácia do cálculo de volume a partir de diferentes métodos de levantamento topográfico

Abstract

Over the past 15 years the GNSS receivers have become quite affordable the civil community, this technology came to represent a tool powerful positioning of modern surveying with innovative contributions in the most diverse fields of research and service, too although it's worth pointing out that some optical measuring equipment still occupy its owing space, especially in places or situations that promote the degradation of the GNSS signal. However the rapid accessibility to this technology and its constant innovation leads to the lack of technical information based on reliable statistical analyzes, about the performance of these receptors compared to optical measuring equipment and the most appropriate way to use according to specific demands. For these reasons the main objective of this research was to carry out the evaluation and comparison of accuracy and altimetric precision of DEMs generated from topographic survey of total station and GNSS receiver in order: (1) kinematic, (2) Stop and Go, and (3) real-time kinematic correction (RTK), for determining the volume material and indicate the most recommended in the cost-benefit ratio. All analyzes were based on the Cartographic Accuracy Standard for Digital Cartographic Products (PEC-PCD) published by the Directorate of Geographic Service of the Brazilian Army (DSG). The surveys were carried out in the wall of the dam Alto Alegre in Caridade municipality of Ceará, with a maximum distance of 500 meters baseline and reference station with 6 hours of screening, post-processed by the online service IBGE-PPP. Along the wall 15 were screened reference points used in evaluate the accuracy from hypothesis testing, where it is held trend analysis and accuracy in comparison with the DEM generated by interpolation in each of the methods. DEM generated through the survey using GNSS Stop and Go mode was the most accurate with very close results to modeling conducted by the kinematic method with realtime correction (RTK), obtaining class A rating for the PEC-PCD with vertical equidistance of 0.64 and 0.8m respectively, This same classification was achieved by the survey in postprocessed kinematic mode (PP) with vertical contour interval of 0.88 m, being that it took less time in the survey, 45 minutes, compared to the others that were more than 2 hours. But the DEM generated from the survey with the total station was unrated by having flunked the evaluation of trend, nevertheless obtained a good result in the accuracy test with vertical equisdistance of 0.83 m and a calculated volume near from the most accurate model, indicating that the trend was not so significant to compromise the end result. From the results it is concluded that for this case study, the most recommended method based on an accuracy analysis and surface evaluation of each call expenses would be the post-processed kinematic mode, since despite being less precise than the GNSS survey Stop and Go, obtained a better cost-benefit ratio and the discrepancy of 5% more in volume wasn't as important for the material in question.