GISTAM 2022 Abstracts


Area 1 - Data Acquisition and Processing

Short Papers
Paper Nr: 1
Title:

Precision Assessment of Artec Space Spider 3D Handheld Scanner for Quantifying Tufa Formation Dynamics on Small Limestone Plates (PLs)

Authors:

Ivan Marić, Ante Šiljeg and Fran Domazetović

Abstract: In this paper precision assessment of the 3D handheld scanner Artec Space Spider was evaluated and critically observed. Namely, a new application of handheld 3D scanners has been found in quantifying tufa formation dynamic (TFD). Such measurements should be characterized by a high level of data quality because tufa usually grows only a few millimeters annually. Therefore, a small limestone plate (PL) used as a substrate on which TFD will be studied was scanned five times by two independent observers. Interval scans of PL were processed using Artec Studio 15 Professional. Data processing consisted of five steps. The precision assessment was determined by statistical analysis of derived sections and colored distance map (CDM). Results showed that Artec Space Spider generates reliable results considering the characteristics of the scanned object and it certainly can be used for TFD analysis. Also, results suggested that the application of Artec Space Spider in the quantification of TFD can be regarded as a better approach in the context of measurement reliability compared to other direct and indirect methods. The subject of future research will be the precision and accuracy assessment of various 3D handheld scanners in scanning tufa formed in different temporal resolutions with various surface complexity.
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Paper Nr: 2
Title:

Multi-Resolution Modeling of the Tufa Formation Dynamic using Close-Range Photogrammetry, Handheld 3D Scanner and Terrestrial Laser Scanner

Authors:

Ivan Marić, Lovre Panđa and Rina Milošević

Abstract: Advances in geospatial technologies (GST) have revolutionized the ability to quantify spatio-temporal changes in various geomorphological forms at different scales. One of the most complex geomorphological forms are tufa and travertine cascades whose evolution is the subject of numerous research in various scientific fields. In this paper, we are presenting a new methodological framework for analyzing tufa formation dynamic (TFD) at three levels of research (macro-meso-micro) using the close-range photogrammetry (CRP) method, handheld 3D scanner, and terrestrial laser scanner (TLS). The results, 3D models and digital elevation models (DEMs), of the first (reference) measurement at three levels of research, are presented in this paper. Reference models were generated using Agisoft Metashape, Artec Studio Professional 15, and SCENE software. Measurements were done in an artificial tufa tunnel, located within the Jaruga, the second oldest hydroelectric power plant in the world constructed within National Park Krka, Croatia. This tunnel is a specific tufa-forming environment. The subject of the next paper will be the comparison of interval tufa 3D tufa models at three levels of research and the calculation of volumetric (mm3 a-1) and linear (mm a−1) tufa growth rates after two years of exposure to the Krka River. The presented methodological framework will expand the knowledge about TFD within this specific depositional sub-environment and can be applied in the dynamic formation analysis of other hydroprecipitates.
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Paper Nr: 3
Title:

Urban Sprawl Analysis in Kutupalong Refugee Camp, Bangladesh

Authors:

Filip Loncar and Pedro Cabral

Abstract: Urban sprawl is a common phenomenon associated with geographical and political challenges such as refugee settlements and environmental extremes. Urban sprawl related to refugee or habitation settlement has been an area of active interest because of humanitarian and environmental problems. For example, higher rates of urban sprawling are positively correlated with higher rates of deforestation. The present study explored the viability and reproducibility of different classification techniques in assessing urban sprawl among Rohingya refugees in the Kutupalong refugee camp in Bangladesh. These classification methods include the Support Vector Machine (SVM) and Maximum Likelihood Classifier (MLC). The urban sprawl was measured based on the classification of urban and non-urban classes. The SVM yielded better overall accuracy performance compared to MLC classification. The study showed that urban class exhibited exponential growth from 2.01 km2 to 5.37 km2 within nine months. On the contrary, the non-urban class shrunk from 12.58 km2 to 9.95 km2 during the same period due to a high influx of refugees and rapid camp expansion.
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Paper Nr: 11
Title:

Multi-parametric Performance Evaluation of Drone-based Surveying for Disaster Risk Management

Authors:

Athina Silvestrou, Andreas M. Georgiou, Panayiotis Kolios and Christos G. Panayiotou

Abstract: Disaster situations, either natural or man-made, could be catastrophic as causes massive destruction of infrastructures or loss of human lives. First-responders should conduct quickly and efficiently to locate survivors; an operation that becomes difficult when the existing infrastructure and the conventional communication might collapse. Unmanned Aerial Vehicles have emerged as a reliable and cost-effective solution, which aids humans in performing such operations by implementing accurate geographical surveying. The proper combination of hardware and software components (for the design and implementation) has to be selected to produce appropriate results, both with respect to output quality and processing time. In this paper, photogrammetric approaches have been investigated in the terms of collection, processing and producing of dense clouds, orthophotos and digital elevation models considering the aforementioned aspects in disaster risk management missions. Thus, different datasets have been collected where the drone-based flight along with sensing parameters were jointly investigated, evaluating the total processing time and model quality. More specific, the following scenarios were investigated: (i) Selection and combination of the photogrammetric method parameters, (ii) Sensor altitude, and (iii) Area division into separated sectors. The decision about the processing software has be done after assessing the capabilities and the limitations of each solution, since this will affect time, quality and cost of the end result. Under this perspective, a commercial and non-commercial tools compared for the data analysis. Finally, the results of each tool were evaluated while the capabilities and limitations have been perceived.
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Paper Nr: 15
Title:

Multi-Sensor 3D Modeling of Natural Heritage: Example of the Lake Zmajevo Oko

Authors:

Lovre Panđa, Ante Šiljeg and Ivan Marić

Abstract: In recent decades geospatial technologies (GST) have been affected by a process of rapid development. One of their applications involves the documentation of the protected areas reference state and the development of high-quality models for their preservation and management. The research area of this paper is Lake Zmajevo oko (Lake Dragon eye), near Rogoznica (Croatia). The research goals were to create a multisensor model of the lake and present the application of these technologies for promotional purposes. The secondary objective was to obtain morphometric data about the lake. The research methodology included performing the process of UAV photogrammetry and bathymetry. In UAV photogrammetry, a Phantom 4 Pro was used. In the bathymetric survey, an integrated system composed of WASSP S3 multibeam depth sounder (MBES) and the Hemisphere V320 GNSS smart antenna was used. The data collected by both methods were combined and an multisensor high-quality model of the lake was created. Ten underwater tunnels on the steep sides of the lake were detected. From the derived models, the volume and surface area of the lake, as well as the length of the lake shoreline were calculated. Furthermore, a virtual walk around the lake was made to promote this area. A physical model of the lake, which can serve as a souvenir, was printed with the 3D printer Prusa i3 MK3. The collected high-quality data can serve as the basis for future research, while derived models and a virtual walk can be used for its promotion.
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Paper Nr: 8
Title:

An In-house, Self-developed Low-cost WebGIS Relying on Open-source and Self-made Tools to Show the Active Deformation Areas across Europe

Authors:

José A. Navarro, Danielly García and Michele Crosetto

Abstract: This paper describes the steps already taken to implement an in-house WebGIS system targeted at displaying Active Deformation Areas for all Europe. The high volume of Persistent Scatterers data (provided by the European Ground Motion Service) to process and afterwards store, together with the economic consequences that such a big volume of information implies were the reasons to prefer an in-house solution instead of using the available, well-stablished cloud-based ones. The architecture of the system as well as the open-source components required to set up a capable server sustaining the said architecture are described in this work, together with the self-developed tools used to implement a production workflow to generate the data (Active Deformation Areas) that will feed such system. Promising preliminary performance figures are also given.
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Paper Nr: 18
Title:

Poverty Population and Its Educational Accessibility: An Evaluation using Geospatial Database in Ecuador

Authors:

Gustavo Navas, Anthony Loyaga, Jefferson Barahona and Julio P. Orellana

Abstract: Education is the most critical aspect against inequality. So, the accessibility to educational centers is one of the biggest problems that governments and academia are trying to solve in Latin America. Finding an optimal location is challenging because different variables can be considered, such as serving the poor, accessing to roads, and optimal distribution. This work presents a methodology that uses geospatial techniques to evaluate the level of access of poor people to educational centers considering location and accessibility. This methodology is multi factorial and can be generalized to multiple scenarios in resource planning. In this work, a case study of Ecuadorian educational centers is analyzed. So, an Ecuadorian geospatial database was created that includes educational centers’ location, the distribution of the poor population, Voronoi diagrams, and road networks. All the analysis were carried out using the PostGIS tool and Google Cloud Platform for the implementation. The results show that 90% of educational centers serve at least 50% of the most impoverished population.
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Paper Nr: 25
Title:

Online Spatial Data Gathering as a Powerful Arm in Urban Management (Study in Iranian Municipality)

Authors:

Mohammad Ghaderi

Abstract: The old version of the spatial data collection method is not so convenient, is expensive and time-consuming it causing the reluctance of municipalities to conduct space surveys. Online spatial data collection is a solution to improve urban data surveys and facilitate relationships between databases. The SDI system as a host is needed to save and collect spatial data, and an application running on a smartphone can locate and send information tables to SDI. By the way, municipalities can define various audit items and investigate functional by simplicity at a lower cost and faster than before.
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Area 2 - Remote Sensing

Short Papers
Paper Nr: 9
Title:

Digital Surface Model Generation with Aerial Surveying System “LEICA ADS80”

Authors:

Vojkan Stanojević, Zlatan Milonjić, Dejan Dordevic, Saša Bakrač, Marko Stojanović and Zoran Stevanović

Abstract: The aerial imaging system LiDAR is data collection technology for Digital Surface Models (DSM) and Digital Elevation Models (DEM). Digital line Pushbroom scanner Leica ADS80 can be used to obtain DSM / DEM thanks to the recorded material. The data obtained using the ADS80 provide several advantages over LiDAR results, especially since the generation of orthophotos can be based on the same data set. As a fundamental approach, the principle of Semi-Global Matching (SGM) it is used, which is suitable for the process of calculating digital models of high-performance and high-resolution surfaces. This paper presents the SGM approach during processing images obtained by the ADS80 system, as well as comparing the results obtained using the LiDAR system - in terms of data processing. A comparative analysis and comparison of SGP and LiDAR ALS80 HP properties was performed, which is illustrated on a specific example. It has been shown that SGM can be used as an alternative to the LiDAR system. For certain applications for which it is necessary to generate a digital model of a high-resolution surface or to make orthophotos - thus saving additional flight costs - SGM is the priority choice.
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Paper Nr: 14
Title:

Selection of Hydrographic Objects in NHD 100K Streams from NHD 24K Streams using Drainage Networks Derived from Digital Elevation Models

Authors:

K. Mirzayev and T. Gökgöz

Abstract: The hydrographic objects in 100K NHD (National Hydrographic Dataset) are conventionally derived by generalization. Besides, drainage networks may also be derived from the digital elevation models according to the stream thresholds. This study aims to derive the streams in 100K NHDs from 24K NHDs by means of drainage networks derived from a 10 m resolution digital elevation models. For this purpose; 1) 24K streams corresponding to 100K streams, 2) 24K streams as many as the number of 24K streams corresponding to 100K streams, 3) 24K streams as many as the number of objects calculated by Töpfer’s formula, and 4) 24K streams as many as the number of midpoints of 24K streams corresponding to 100K streams are selected by means of drainage networks derived from a 10 m resolution digital elevation model. Twelve experiments were conducted to test the suitability of the four approaches in three sub basins (i.e. Big Run, Seneca and Strait in South Branch Potomac Basin in the WV, USA) chosen as the study areas. As a result, none of the approaches was able to select all 24K streams corresponding to 100K streams without any over- or under-represented 24K streams.
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Paper Nr: 19
Title:

Establishing Surface Displacements along a Railway Route near Mirovo Salt Deposit, NE Bulgaria

Authors:

Mila Atanasova-Zlatareva and Hristo Nikolov

Abstract: Studying Earths’ surface motions using data acquired by active instruments such as satellite Synthetic Aperture Radar (SAR) have become ubiquitous in the last years. This trend could be attributed to large extent to the open data policy of ESA that provides such type data from Sentinel-1 mission at no cost from several online repositories. On the other hand the results produced after processing them need to be validated by data from other sources. In this paper a framework for SAR data processing is presented, whose results are compared and analysed with results from GNSS networks. In order to increase the reliability of the information provided by the radar data used in this research ascending and descending orbits of the satellite were used in order to decrease the effect of the topography. Part of railway line which passes through the town of Provadia and industrial area near it was selected as test site. This object was chosen since surface deformations often occur in it caused by natural and anthropogenic activities in that area.
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Area 3 - Modeling, Representation and Visualization

Full Papers
Paper Nr: 5
Title:

Mobile Outdoor AR Application for Precise Visualization of Wind Turbines using Digital Surface Models

Authors:

Simon Burkard and Frank Fuchs-Kittowski

Abstract: Realistic visualizations illustrating the visual impact of planned large structures and buildings in the landscape are challenging and often difficult to create. In this paper, a mobile outdoor augmented reality application is presented that enables realistic and immediate on-site visualization of planned wind turbines at their intended geographic location superimposed on the live camera image of mobile devices. For this purpose, a manual localization procedure is described that uses 3D geospatial models (e.g., digital surface models) displayed in the camera view to enable precise global orientation and positioning of the mobile device resulting in very realistic AR visualizations. In addition, the functions, implementation details and evaluation results of the mobile application are presented.
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Short Papers
Paper Nr: 7
Title:

Suitability Analysis as a Recommendation System for Housing Search

Authors:

Jaskaran S. Puri and Pedro Cabral

Abstract: The metropolitan cities are facing a huge skewness of service distribution that is given in different parts of the same city. Given the rapid increase in immigration, the quality-of-life factors are often left out while performing housing searches. This paper explores the ideal sub-regions in Delhi, India, for living based on different lifestyle profiles. Using suitability analysis, it is possible to personalize a geographical area for housing. Five such factors, namely, rental budget, commute time, green landscape, pollution, and food accessibility were considered. Four different user profiles (18-65) and their importance to each of the factors were simulated. The range of each variable was standardized using transformations. Data was obtained from data-hubs like Kaggle, OSM, and GEE. The analysis was supported by ArcGIS Pro to get district-level features and suitability modelling. The commute variable is a derived variable from the cost surface raster and AQI values from the weather stations were used. Four different suitability maps are generated using multi-criteria evaluation. This automated approach can be useful for customers and agents to find or consult housing for immigrants by making it personalized and providing insights to better explain consumer behaviour based on spatial attributes, hence making spatially intelligent tools.
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Area 4 - Knowledge Extraction and Management

Full Papers
Paper Nr: 6
Title:

A Formally Correct and Algorithmically Efficient LULC Change Model-building Environment

Authors:

François-Rémi Mazy and Pierre-Yves Longaretti

Abstract: The use of spatially explicit land use and land cover (LULC) change models is widespread in environmental sciences and of interest in public decision-help. However, it appears that these models suffer from significant biases and shortcomings, the sources of which can be mathematical, conceptual or algorithmic. We formalize a modeling environment that distinguishes a calibration-estimation module and an allocation module. We propose an accurate calibration-estimation method based on kernel density estimation and detail an unbiased allocation algorithm. Moreover, a method of evaluation of LULC change models is presented and allows us to compare them on various fronts (accuracy, biases, computational efficiency). A case study based on a real land use map but with known (enforced) transition probabilities is used. It appears that the estimation error of the methods we propose is substantially improved over the best existing software. Moreover, these methods require the specification of very few parameters by the user, and are numerically efficient. This article presents an overview of our LULC change modeling framework; its various formal and algorithmic constituents will be detailed in forthcoming papers.
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Paper Nr: 12
Title:

Comparison of Free and Open PPP Services for Master-base Positioning in Geodetic Disadvantaged Areas: Case Study along the Sirba River in Sub-Saharan Africa

Authors:

Elena Belcore, Marco Piras, Paolo Dabove, Giovanni Massazza and Maurizio Rosso

Abstract: The Precise Point Positioning (PPP) is a Global Navigation Satellite System (GNSS technique) for post- and real-time processing. PPP has recently spread thanks to the high precision and accuracy positioning results that it provides. Until some years ago, this technique was limited by long sessions of measurements and professional software to obtain results with centimetre-level precision, using only one GNSS dual frequency receiver. Nowadays, the PPP technique is well established among GNSS experts, and many software exists to perform it. The PPP technique uses data from continuously operating reference stations (CORS) to process the pseudo-range and carrier phase measurements. CORS can also be located very far from the surveyed area. This makes PPP particularly suitable for GNSS surveys in areas considered disadvantaged for the lack of geodetic infrastructures, such as CORS and known-coordinates points. Recently, PPP online free and open tools have been made available by national agencies worldwide. This contribution analyses the PPP online services as potential solutions for realising GNSS surveys in geodetic disadvantaged areas. Specifically, it compares two PPP online services: the Canadian Spatial Reference System Precise Point Positioning tool (CSRS-PPP) and Automatic Precise Positioning Service (APPS). In the analysis, the AUSPOS Online GPS processing service that applies relative positioning technique based on the closest CORS was considered a non-PPP post-processing online tool to compare results. Data were collected in South-West Niger, along Sirba River, 900 km away from the closest CORS and 250 km far from the closest known-coordinates point. The estimated coordinates' precision was tested for different session lengths (three scenarios of 3 hours, 1 hour, and 30 minutes) over 17 sessions. Then, the precision was validated by analysing the one-year daily acquisitions dataset (from CORS). The results revealed precisions and relative accuracies lower than 5 cm for three hours' sessions. From the analysis of the short stationing sessions (i.e., one hour and half hour) emerged that APPS provides the most confident solutions. As expected, the less performant service in CORS- depressed areas is the relative positioning service AUSPOS.
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Area 5 - Domain Applications

Full Papers
Paper Nr: 23
Title:

Assessing Informal Trails Impacts and Fragmentation Effects on Protected Areas using Volunteered Geographic Information

Authors:

Luís Monteiro and Pedro Cabral

Abstract: Informal trails represent an important visitor-related impact on the natural resources of recreational and protected areas by compacting soil, changing vegetation composition, moving wildlife, altering the hydrological cycle, and fragmenting landscapes. This paper develops an approach to assess the extent of the informal trails network and their trail-based impacts in a protected area within the Lisbon Metropolitan Area, Portugal. A total of 28.911,254 km of Volunteered Geographic Information tracks were collected from a fitness and travel web platform. Spatial analysis was performed to assess the extent of the informal infrastructure, and landscape metrics were used to understand the diversity of trail-based fragmentation across the area. A total of 669,6 km were mapped as potential informal trails, hiking being the most popular activity using this infrastructure. Approximately 58% of higher protection areas have been fragmented by informal trails development, representing a loss in the size and integrity of endangered habitat. The proposed approach allowed to produce a significant coverage of information about the levels of impact from informal trails at the landscape scale using a minimal amount of resources. Further work is recommended to validate results at the local scale using onsite trail-based assessments.
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Paper Nr: 26
Title:

A Spatially Detailed Approach to the Assessment of Rooftop Solar Energy Potential based on LiDAR Data

Authors:

Mohammad Aslani and Stefan Seipel

Abstract: Rooftop solar energy has long been regarded as a promising solution to cities’ growing energy demand and environmental problems. A reliable estimate of rooftop solar energy facilitates the deployment of photovoltaics and helps formulate renewable-related policies. This reliable estimate underpins the necessity of accurately pinpointing the areas utilizable for mounting photovoltaics. The size, shape, and superstructures of rooftops as well as shadow effects are the important factors that have a considerable impact on utilizable areas. In this study, the utilizable areas and solar energy potential of rooftops are estimated by considering the mentioned factors using a three-step methodology. The first step involves training PointNet++, a deep network for object detection in point clouds, to recognize rooftops in LiDAR data. Second, planar segments of rooftops are extracted using clustering. Finally, areas that receive sufficient solar irradiation, have an appropriate size, and fulfill photovoltaic installation requirements are identified using morphological operations and predefined thresholds. The obtained results show high accuracy for rooftop extraction (93%) and plane segmentation (99%). Moreover, the spatially detailed analysis indicates that 17% of rooftop areas are usable for photovoltaics.
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Short Papers
Paper Nr: 10
Title:

Analysis of Coastline Evolution using Landsat and Sentinel 2 Images from 2001 to 2020 in Callao Bay, Peru

Authors:

Amanda Muñoz, Luis Mendoza, Emanuel Guzmán and Carmela Ramos

Abstract: The study presented an analysis of the shoreline evolution in Callao Bay – Lima, Perú; which is one of the most important bays in Perú due to economics and touristic activities. Study areas include La Punta, Callao and Ventanilla districts with an approximate 32 km of length. The study area was divided into six sectors, and the analysis was focused mainly from the 2001 to 2020 period, identifying areas affected by coastal erosion or accretion throughout. Satellite data images were obtained from Landsat (5, 7 and 8) and Sentinel 2, they were processed to correctly identify the shoreline. Shoreline variations were analyzed using the DSAS (Digital Shoreline Analysis System) utility, applying a statistical method called "Linear Regression Ratio". Shoreline variations showed different rates of changes along different sectors of the study area. In general terms, the accretion or erosion trend in Callao Bay was a low accretion with average rates from 3.77 m / year to 4.20 m / year, except in the sector which is closed to the Rímac river with change rate of around 11.85 m/year.
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Paper Nr: 28
Title:

Sea Level Rise Future Predictions: A Case Study in Crete

Authors:

Antigoni Panagiotopoulou, Lemonia Ragia and Froso Sarri

Abstract: This work presents an estimation approach for coastal data with regard to climate change. Specifically, future sea level rise (SLR) values are predicted on the basis of initial corresponding values, which are identical to the values for the year 2025 that are provided by the Mediterranean Coastal Database (MCD). The proposed estimator is named Coastal Data Estimator (CDE) and is used for predictions in the Crete island, Greece. During the years from 2030 to 2100, the CDE estimation performance is evaluated against the MCD regarding the representative concentration pathways 2.6 (RCP26), 4.5 (RCP45) and 8.5 (RCP85) as well as the medium and high ice-sheet melting scenarios. Concerning the high ice-sheet melting scenario in RCP26, the CDE deviates less than 10% for the years 2030-2065 and 2080-2100. In the case of RCP45, the CDE estimator achieves predictions with deviations less than 10% from the year 2030 to the year 2080 and 2075 for medium and high scenario, correspondingly. Future work includes the CDE testing in other Mediterranean sites. Additionally, the CDE equation could become multibranch as well as estimations should be automized, excluding the per year constants.
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