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Boletim de Ciências Geodésicas, Volume: 28, Issue: 4, Published: 2022
  • Assessment of GPS positioning performance using different signals in the context of ionospheric scintillation: a month-long case study on São José dos Campos, Brazil Original Article

    Souza, Ana Lucia Christovam de; Jerez, Gabriel Oliveira; Camargo, Paulo de Oliveira; Alves, Daniele Barroca Marra

    Abstract in English:

    Abstract: The ionospheric scintillation associated to small-scale irregularities in the ionospheric layer can lead to performance degradation of Global Navigation Satellite Systems (GNSS) signals, and the reduction of positioning accuracy. The influence of the ionospheric layer on the GNSS systems is expected to be different for each signal since it is transmitted on different carrier frequencies. This paper presents the results of a quantitative analysis of the scintillation amplitude of GPS (Global Positioning System) signals at L1, L2 and L5 frequencies, aiming to evaluate the impact of the ionospheric scintillation effects on the GPS frequencies. As the ionospheric scintillation may impact positioning accuracy, we also present an assessment of GPS point positioning using those frequencies. The GPS sample data were collected for 30 days between November and December 2014 at SJCE station located in São José dos Campos (SP), Brazil. Such a region is subjected to the equatorial anomaly effects being characterized by the occurrence of strong ionosphere scintillation. Considering the quantitative analysis, during the different levels of ionospheric scintillation presented a similar behavior, the magnitude of scintillations is small for the L1 signal and larger for L5. In general, the results confirmed that lower frequencies (L2 and L5) suffer more impact from intense scintillation than L1. Regarding the positioning assessment, the multi-frequency positioning was more accurate than single frequency. Considering dual-frequency positioning, results with L1-L2 were more accurate than those with L1-L5 signals. With single-frequency positioning, the L1 signal was more accurate compared to the L2 frequency.
  • Enhancing SRTM digital elevation models with deep-learning-based super-resolution image generation Original Article

    Moreira, Leonardo Assumpção; Poelking, Livia Moreira; Araki, Hideo

    Abstract in English:

    Abstract: Digital elevation models are responsible for providing altimetric information on a surface to be mapped. While global models of low and medium spatial resolution are available open source by several space agencies, the high-resolution ones, which are utilized in scales 1:25,000 and larger, are scarce and expensive. Here we address this limitation by the utilization of deep learning algorithms coupled with SISR techniques in digital elevation models to obtain better spatial quality versions from lower resolution inputs. The development of a GAN-based methodology enables the improvement of the initial spatial resolution of low-resolution images. A dataset with different pairs of digital elevation models was created with the objective of allowing the study to be carried out, promoting the emergence of new research groups in the area as well as enabling the comparison between the results obtained. It has been found that by increasing the number of iterations the performance of the generated model was improved and the quality of the generated image increased. Furthermore, the visual analysis of the generated image against the high- and low-resolution ones showed a great similarity between the first two.
  • Characterisation of stakeholders' roles in a thematic SDI: a study on the environmental SDI of NGI - ICMBio Antonina -GUARAQUEÇABA - PR Original Article

    Silva, Josemar Pereira da; Camboim, Silvana Philippi; Paula, Eduardo Vedor de

    Abstract in English:

    Abstract: In 2008 the International Cartographic Association (ICA) proposed a reference model to describe Spatial Data Infrastructures (SDI) based on the Reference Model of Open Distributed Processing (RM-ODP), which has been adapted and validated by several research projects. This paper details the experience of applying the extended ICA Model to an Academic SDI of environmental character and collaborative functions, such as the description of stakeholders' roles, functions, and responsibilities, called IDE-AMB (acronym in Portuguese). The intent is to transform the IDE-AMB into a database composed of information from several institutions and academic research. The stakeholders were described based on previously established literature and their needs for access, use, production, and sharing of geospatial data from different sources for the Integrated Management Center (NGI, acronym in Portuguese) ICMBio Antonina-Guaraqueçaba, located on the northern coast of the state of Paraná. We concluded that the ICA Model presents robustness; however, it still lacks conceptual reviews and needs to be adapted to the new realities and complexities of emerging SDI.
  • Partially-conformal variations of the Standard Molodensky datum transformation Original Article

    Ruffhead, Andrew Carey

    Abstract in English:

    Abstract: Standard Molodensky is a recognised method of transforming coordinates between geodetic datums. Although less accurate than some other methods, it has the merit of being direct. That is to say it can be applied to geodetic coordinates, without involving Cartesian coordinates that give rise to difficulties in computing latitude. This paper considers the use of Standard Molodensky when at least one of the datums is 2D+1D in nature, meaning that that horizontal and vertical positions are obtained by different methods. This was generally the case before 3D positioning by satellites and is a widespread characteristic of local datums that are still used. The 2D+1D property weakens the argument for 3D conformality, and invites the possibility that different translation parameters might be used for horizontal and vertical shifts. The possibility of including a Z-rotation as a 7th parameter is also considered. Besides being ideal for those who favour the simplicity of Standard Molodensky, the variations introduced in this paper offer significant improvements in accuracy such as error reductions of 75%, 69% and 99% in the three selected case studies.
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