Vertical Accuracy Assessment of ALOS PALSAR, GMTED2010, SRTM and Topodata Digital Elevation Models

Ferreira, Z. A., & Cabral, P. (2021). Vertical Accuracy Assessment of ALOS PALSAR, GMTED2010, SRTM and Topodata Digital Elevation Models. In Proceedings of the 7th International Conference on Geographical Information Systems Theory, Applications and Management (GISTAM 2021) (pp. 116-124). SCITEPRESS - Science and Technology Publications, Lda. https://doi.org/10.5220/0010404001160124Three-dimensional data of the Earth's surface can support several types of studies, such as hydrological, geomorphological, environmental monitoring, among many others. But, due to the difficulty of acquiring these data in the field, freely available Digital Elevation Models (DEM) have been widely used, and therefore, it is increasingly necessary to check their accuracy to ensure their correct applicability according to the appropriate scale. However, there are no studies which have assessed specifically the vertical accuracy of the ALOS PALSAR, GMTED2010, SRTM and Topodata DEMs according to Brazilian Cartographic Accuracy Standard (PEC). In this sense, this paper aims to evaluate the quality of the above-mentioned DEMs by using the official high accuracy altimetric network data of the Brazilian Geodetic System. Statistical analysis of errors results demonstrated that the DEMs have applications compatible with 1:100,000 scales or smaller than this, and although the GMTED2010 presented a lower accuracy than the other DEMs, it also could be classified in the same accuracy category according to the Brazilian PEC. We conclude that DEMs assessment is very important to ensure their correct application as they can be used in many researches since these data are available for practically all areas of the planet.publishersversionpublishe

GNSS Positioning using Android Smartphone

The possibility to manage pseudorange and carrier-phase measurements from the Global Navigation Satellite System (GNSS) chipset installed on smartphones and tablets with an Android operating system has changed the concept of precise positioning with portable devices. The goal of this work is to compare the positioning performances obtained with a smartphone and an external mass-market GNSS receiver both in real-time and post-processing. The attention is also focused not only on the accuracy and precision, but also on the possibility to determine the phase ambiguity values as integer (fixed positioning) that it is still a challenging aspect for mass-market devices: if the mass-market receiver provides good results under all points of view both for real-time and post-processing solutions (with precisions and accuracies of about 5 cm and 1 cm, respectively), the smartphone has a bad behaviour (order of magnitude of some meters) due to the noise of its measurements

Evaluating the Impact of the Urban Requalification Project of Praça Duque De Saldanha and Avenida Da República in Lisbon

UID/SOC/04647/2013 SFRH/BPD/76893/2011In dense urban areas, reducing traffic and increasing green areas is foreseen as a way of promoting urban comfort. Using the urban requalification project for Lisbon’s Avenidas Novas neighbourhood as a case study, the effects of vegetation on microclimate and urban comfort are evaluated. In this context, the ENVI-met software is used to model the present and the future urban scenario. The simulation results indicate: i) increased urban comfort in the morning and in the afternoon resulting from the decrease in temperature due to the presence of new green areas foreseen by the urban project; ii) a reduction of up to 3 degrees in the morning (9h) and up to 3 degrees in the afternoon (15h); iii) the model implemented in ENVI-met suits the urban and environmental characteristics of Lisbon and it is, therefore, desirable that future urban rehabilitation projects should consider ex ante simulation of this typepublishersversionpublishe

Exploring Spectral Data, Change Detection Information and Trajectories for Land Cover Monitoring over a Fire-Prone Area of Portugal

Alves, A.; Moraes, D.; Barbosa, B.; Costa, H.; Moreira, F.; Benevides, P.; Caetano, M. and Campagnolo, M. (2023). Exploring Spectral Data, Change Detection Information and Trajectories for Land Cover Monitoring over a Fire-Prone Area of Portugal. In Proceedings of the 9th International Conference on Geographical Information Systems Theory, Applications and Management - GISTAM; ISBN 978-989-758-649-1; ISSN 2184-500X, SciTePress, pages 87-97. DOI: 10.5220/0011993100003473---This research was conducted under the collaboration contract DGT-ISA 261/2021 with funding from Compete2020 (POCI-05-5762-FSE-000368), supported by the European Social Fund, and Centro Exploring Spectral Data, Change Detection Information and Trajectories for Land Cover Monitoring over a Fire-Prone Area of Portugal 95 de Investigação em Gestão de Informação (MagIC), Project UIDB/00239/2020 (Forest Research Centre), both supported by the Portuguese Foundation for Science and Technology (FCT)Land use/land cover (LULC) change detection and classification in maps based on automated data processing are becoming increasingly sophisticated in Earth Observation (EO). There is a growing number of annual maps available, with diverse but related production structures consisting primarily of classification and post-classification phases, the latter of which deals with inaccuracies of the first. The methodology production of the “Carta de Ocupação do Solo conjuntural” (COSc), a thematic land cover map of continental Portugal produced by the Directorate-General for Territory (DGT) mostly based on Sentinel-2 images classification, includes a semi-automatic phase of correction that combines expert knowledge and ancillary data in if-then-else rules validated by photointerpretation. Although this approach reduces misclassifications from an initial Random Forest (RF) prediction map, improving consistency between years and compliance with ecological succession, requires a lot of time-consuming semi-automatic procedures. This work evaluates the relevance of exploring an additional set of variables for automatic classification over disturbance-prone areas. A multitemporal dataset with 124 variables was analysed using data dimensionality reduction techniques, resulting in the identification of 35 major explanatory indicators, which were then used as inputs for RF classification with cross-validation. The estimated importance of the explanatory variables shows that composites of spectral bands, which are already included in the current COSc workflow, in conjunction with the inclusion of additional data namely, historical land cover information and change detection coefficients, from the Continuous Change Detection and Classification (CCDC) algorithm, are relevant for predicting land cover classes after disturbance. Since map updating is a more challenging task for disturbed pixels, we focused our analysis on locations where COSc indicated potential land cover change. Nonetheless, the overall classification accuracy for our experiments was 72.34 % which is similar to the accuracy of COSc for this region of Portugal. The findings suggest new variables that could improve future COSc maps.publishersversionpublishe

A Multiscale Framework Based on Global Geospatial Data

Almeida, B. and Cabral, P. (2023). Data-Driven Modelling of Freshwater Ecosystems: A Multiscale Framework Based on Global Geospatial Data. In Proceedings of the 9th International Conference on Geographical Information Systems Theory, Applications and Management - GISTAM; ISBN 978-989-758-649-1; ISSN 2184-500X, SciTePress, pages 104-111. DOI: 10.5220/0012037800003473---This work was supported by the research project MaSOT – Mapping Ecosystem Services from Earth Observations, funded by the Portuguese Science Foundation – FCT [EXPL/CTA-AMB/0165/2021], and by national funds through FCT (Fundação para a Ciência e a Tecnologia), under the project - UIDB/04152/2020 - Centro de Investigação em Gestão de Informação (MagIC)/NOVA IMSFreshwater ecosystems are primarily impacted by climate, land use and land cover changes, and over-abstraction. Satellite Earth observation (SEO) data and technologies are key in environmental modelling and support decisions. These technologies combined with machine learning (ML) are a powerful approach for modelling freshwater ecosystems at a multiscale level. The goal of this study is to present a set of reference data and guidelines that can be used to estimate the water and wetness probability index (WWPI) in different spatial and temporal scales. To find the best model’s predictors, sensitivity analyses were carried out in a predictive ML model implemented in a transnational river basin district (Portugal – Spain), the Tagus Basin. Satellite imagery, satellite-derived data, biophysical variables, and landscape characteristics were the explanatory variables evaluated in the sensitivity analyses, and some of them were included in the framework as a reference source of spatial data.publishersversionpublishe

A Newly Emerging Ethical Problem in PGIS : Ubiquitous Atoque Absconditus and Casual Offenders for Pleasure

Thanks to the recent technological advances of cellular phones, the practical realization of GeoAPI and SNS, and the consolidation of wireless LAN networks, hardware has become capable of providing portable highspeed Internet access and interactive SNS, and people can now easily communicate far more, casually and unboundedly, via the Internet. Currently, PGIS studies mainly look at the ‘sunny side’ of GIT progress. Although there are also relevant studies on online ethics, they rely unduly on spontaneously arising equilibrium innervated by mutual surveillance among the people involved. However, it is an over-optimistic and ingenuous perception regarding this exponential technological advance. In this paper, the author illustrates the existence of ‘casual offenders for pleasure’ by referring to two recent online cyberbullying incidents. Because the appreciation of technology-aided ubiquitous mapping can be very hard to see or to grasp, especially for people not educated and trained to see it, the advances prompt people to nonchalantly lower technical and ethical barriers. Further studies are essential to establish the geographic information ethics and offer a clear-cut answer for this newly emerging problem

Management and creation of a new tourist route in the National Park of the Sibillini Mountains using GIS Software, for economic development

This analysis is focused in a small portion of territory in central Italy where the National Park of Sibillini mountains is located. This Park strongly needs a tourist and economic development, so the possibility of creating a new tourist route has been considered. GIS software was used to create and manage the route, using orthophotos and digitizing the required data. The main goal of this study is represented by the creation of an evaluation system for the route, composed by numerous informations managed statistically through GIS software, assessing slope, type of route, road surface, hiking difficulties and passage through towns. This procedure allows a significant improvement in the local economy and a more rational use of available resources, including human ones

Applications of geographic information systems

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