| 1. |
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| 2. |
- Brandt, S. Anders, 1970-, et al.
(författare)
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Kartografiska Sällskapets utbildningssektion : ett nytt tillskott i KS-familjen
- 2006
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Ingår i: Kart- & bildteknik. - Gävle : Kartografiska sällskapet. - 1651-792X. ; 21:2, s. 10-11
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- På Kartografiska Sällskapets årsmöte i Jönköping den 21 mars beslutades att inrätta en ny sektion inom sällskapet – en utbildningssektion. Denna artikel beskriver bakgrunden till sektionen och dess verksamhetsidé. Utbildningssektionens embryo tillkom för tre år sedan efter förslag från ULI som delegerade uppgiften till Geomatikprogrammet vid Högskolan i Gävle. Tanken vara att skapa ett forum för lärare inom geomatikområdet. Både för att sammanföra lärare från olika lärosäten, för att öka förståelsen för varandras arbeten, och för att kunna förbättra möjligheterna till samarbete.
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| 3. |
- Brandt, S. Anders, 1970-, et al.
(författare)
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3D geovisualization as a communication and analysis tool in fluvial geomorphology
- 2004
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Ingår i: Geoinformatics 2004. - Gävle : Gävle University Press. - 919749481X ; , s. 339-346
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Konferensbidrag (refereegranskat)abstract
- The fields of hydrology and fluvial geomorphology get more and more attention in the general public. The reason for this is changed climate patterns with increased frequencies of storms and river flooding and as a result changed geomorphology and living conditions for the inhabitants of the area. With the development of 3D geovisualization, hydrological and geomorphological processes can be better simulated and visualized. Thus not only the domain specialists, but also the general public can appreciate very complex hydrological processes and resulting geomorphology. This is of great value since a high frequency of storms and flooding has been a big issue for politicians, planners, and the general public. It is in this sense that 3D geovisualization can be an important tool for analysis and communication. Complex hydrological and geomorphological processes can be effectively simulated and analyzed by the domain specialists while efficient and effective visualization provides a common platform for communication among domain specialists and the general public. This paper will discuss and illustrate these issues using a case study of geomorphology along the Reventazón River, downstream from the Cachí Reservoir in Costa Rica, due to the release of extreme amounts of sediment during flushing of the reservoir.
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| 4. |
- Brandt, S. Anders, 1970-
(författare)
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Conceptualization of hydraulic and sedimentary processes in downstream reaches during flushing of reservoirs
- 2005
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Ingår i: Proceedings of the XXXI IAHR Congress [Elektronisk resurs]. - Seoul : Korea Water Resources Association. - 8987898237 ; , s. 2577-2588
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Konferensbidrag (refereegranskat)abstract
- The main focus of this paper is to describe the active hydraulic and sedimentary processes in downstream river reaches during flushing of sediments from reservoirs. During flushing extreme amounts of sediment may be released. Therefore, these processes are different than those downstream from dams and reservoirs not subjected to flushing. Hence, also the effects differ, which knowledge of may be of value for biologists, etc. During flushing of a reservoir a wave will be released to the downstream reaches. This wave can be divided into one water part and one sediment part. Initially they are in phase with each other, but with increased distance downstream from the dam, the transported sediment lags behind the water due to different traveling velocities. The paper treats when and where sedimentation occurs, and how this is related to the different traveling velocities of water and sediment. Also included are discussions on how the downstream effects during flushing differ from non-flushing effects, how visualization of effects can enhance both the analysis and communication with planners, politicians, etc., as well as discussions on how the studies of these effects can benefit from improved field-work methods.
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| 5. |
- Lim, Nancy Joy, 1980-, et al.
(författare)
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Visualisation and evaluation of flood uncertainties based on ensemble modelling
- 2016
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Ingår i: International Journal of Geographical Information Science. - : Taylor & Francis. - 1365-8816 .- 1365-8824 .- 1362-3087. ; 30:2, s. 240-262
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Tidskriftsartikel (refereegranskat)abstract
- This study evaluates how users incorporate visualisation of flood uncertainty information in decision-making. An experiment was conducted where participants were given the task to decide building locations, taking into account homeowners’ preferences as well as dilemmas imposed by flood risks at the site. Two general types of visualisations for presenting uncertainties from ensemble modelling were evaluated: (1) uncertainty maps, which used aggregated ensemble results; and (2) performance bars showing all individual simulation outputs from the ensemble. Both were supplemented with either two-dimensional (2D) or three-dimensional (3D) contextual information, to give an overview of the area.The results showed that the type of uncertainty visualisation was highly influential on users’ decisions, whereas the representation of the contextual information (2D or 3D) was not. Visualisation with performance bars was more intuitive and effective for the task performed than the uncertainty map. It clearly affected users’ decisions in avoiding certain-to-be-flooded areas. Patterns to which the distances were decided from the homeowners’ preferred positions and the uncertainties were similar, when the 2D and 3D map models were used side by side with the uncertainty map. On the other hand, contextual information affected the time to solve the task. With the 3D map, it took the participants longer time to decide the locations, compared with the other combinations using the 2D model.Designing the visualisation so as to provide more detailed information made respondents avoid dangerous decisions. This has also led to less variation in their overall responses.
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| 6. |
- Samuelsson, Karl, et al.
(författare)
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Impact of environment on people’s everyday experiences in Stockholm
- 2018
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Ingår i: Landscape and Urban Planning. - : Elsevier BV. - 0169-2046 .- 1872-6062. ; 171, s. 7-17
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Tidskriftsartikel (refereegranskat)abstract
- In order to construct urban environments that limit negative impacts for global sustainability while supporting human wellbeing, there is a need to better understand how features of the environment influence people’s everyday experiences. We present a novel method for studying this combining accessibility analysis and public participatory GIS (PPGIS). Seven environment features are defined and accessibility to them analysed across Stockholm municipality. We estimate the probabilities of positive and negative experiences in places based on these environment features, by using spatial regression to extrapolate from the results of an online PPGIS survey (1784 experiences of 1032 respondents). Six of the seven studied environment features have significant impact on experiential outcome, after accounting for spatial autocorrelation among the data. The results show that number of residents and proximity of nature environments and water, all common quality indicators in urban planning and research, have weak statistically significant effects on people’s experiences. However, areas dominated by large working populations or proximity to major roads have very low rates of positive experiences, while areas with high natural temperature regulating capacities have very high rates, showing that there are considerable qualitative differences within urban environments as well as nature environments. Current urban planning practices need to acknowledge these differences to limit impacts on the biosphere while promoting human wellbeing. We suggest that a good way to start addressing this is through transformation of negatively experienced urban areas through designs that integrate closeness to urbanity with possibilities to have nature experiences on a daily basis.
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| 7. |
- Brandt, S. Anders, 1970-
(författare)
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Modeling and visualizing uncertainties of flood boundary delineation : algorithm for slope and DEM resolution dependencies of 1D hydraulic models
- 2016
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Ingår i: Stochastic environmental research and risk assessment (Print). - : Springer. - 1436-3240 .- 1436-3259. ; 30:6, s. 1677-1690
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Tidskriftsartikel (refereegranskat)abstract
- As flood inundation risk maps have become a central piece of information for both urban and risk management planning, also a need to assess the accuracies and uncertainties of these maps has emerged. Most maps show the inundation boundaries as crisp lines on visually appealing maps, whereby many planners and decision makers, among others, automatically believe the boundaries are both accurate and reliable. However, as this study shows, probably all such maps, even those that are based on high-resolution digital elevation models (DEMs), have immanent uncertainties which can be directly related to both DEM resolution and the steepness of terrain slopes perpendicular to the river flow direction. Based on a number of degenerated DEMs, covering areas along the Eskilstuna River, Sweden, these uncertainties have been quantified into an empirically-derived disparity distance equation, yielding values of distance between true and modeled inundation boundary location. Using the inundation polygon, the DEM, a value representing the DEM resolution, and the desired level of confidence as inputs in a new-developed algorithm that utilizes the disparity distance equation, the slope and DEM dependent uncertainties can be directly visualized on a map. The implications of this strategy should benefit planning and help reduce high costs of floods where infrastructure, etc., have been placed in flood-prone areas without enough consideration of map uncertainties.
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| 8. |
- Aslani, Mohammad
(författare)
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Computational and spatial analyses of rooftops for urban solar energy planning
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In cities where land availability is limited, rooftop photovoltaic panels (RPVs) offer high potential for satisfying concentrated urban energy demand by using only rooftop areas. However, accurate estimation of RPVs potential in relation to their spatial distribution is indispensable for successful energy planning. Classification, plane segmentation, and spatial analysis are three important aspects in this context. Classification enables extracting rooftops and allows for estimating solar energy potential based on existing training samples. Plane segmentation helps to characterize rooftops by extracting their planar patches. Additionally, spatial analyses enable the identification of rooftop utilizable areas for placing RPVs. This dissertation aims to address some issues associated with these three aspects, particularly (a) training support vector machines (SVMs) in large datasets, (b) plane segmentation of rooftops, and (c) identification of utilizable areas for RPVs. SVMs are among the most potent classifiers and have a solid theoretical foundation. However, they have high time complexity in their training phase, making them inapplicable in large datasets. Two new instance selection methods were proposed to accelerate the training phase of SVMs. The methods are based on locality-sensitive hashing and are capable of handling large datasets. As an application, they were incorporated into a rooftop extraction procedure, followed by plane segmentation. Plane segmentation of rooftops for the purpose of solar energy potential estimation should have a low risk of overlooking superstructures, which play an essential role in the placement of RPVs. Two new methods for plane segmentation in high-resolution digital surface models were thus developed. They have an acceptable level of accuracy and can successfully extract planar segments by considering superstructures. Not all areas of planar segments are utilizable for mounting RPVs, and some factors may further limit their useability. Two spatial methods for identifying RPV-utilizable areas were developed in this realm. They scrutinize extracted planar segments by considering panel installation regulations, solar irradiation, roof geometry, and occlusion, which are necessary for a realistic assessment of RPVs potential. All six proposed methods in this thesis were thoroughly evaluated, and the experimental results show that they can successfully achieve the objectives for which they were designed.
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| 9. |
- Kordi, Maryam, 1979-, et al.
(författare)
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Effects of increasing fuzziness on analytic hierarchy process for spatial multicriteria decision analysis
- 2012
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Ingår i: Computers, Environment and Urban Systems. - : Elsevier. - 0198-9715 .- 1873-7587. ; 36:1, s. 43-53
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Tidskriftsartikel (refereegranskat)abstract
- Multicriteria decision analysis (MCDA) involves techniques which relatively recently have received great increase in interest for their capabilities of solving spatial decision problems. One of the most frequently used techniques of MCDA is Analytic Hierarchy Process (AHP). In the AHP, decision-makers make pairwise comparisons between different criteria to obtain values of their relative importance. The AHP initially only dealt with crisp numbers or exact values in the pairwise comparisons, but later it has been modified and adapted to also consider fuzzy values. It is necessary to empirically validate the ability of the fuzzified AHP for solving spatial problems. Further, the effects of different levels of fuzzification on the method have to be studied. In the context of a hypothetical GIS-based decision-making problem of locating a dam in Costa Rica using real-world data, this paper illustrates and compares the effects of increasing levels of uncertainty exemplified through different levels of fuzzification of the AHP. Practical comparison of the methods in this work, in accordance with the theoretical research, revealed that by increasing the level of uncertainty or fuzziness in the fuzzy AHP, differences between results of the conventional and fuzzy AHPs become more significant. These differences in the results of the methods may affect the final decisions in decision-making processes. This study concludes that the AHP is sensitive to the level of fuzzification and decision-makers should be aware of this sensitivity while using the fuzzy AHP. Furthermore, the methodology described may serve as a guideline on how to perform a sensitivity analysis in spatial MCDA. Depending on the character of criteria weights, i.e. the degree of fuzzification, and its impact on the results of a selected decision rule (e.g. AHP), the results from a fuzzy analysis may be used to produce sensitivity estimates for crisp AHP MCDA methods.
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| 10. |
- Lim, Nancy Joy, 1980-, et al.
(författare)
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Are Feature Agreement Statistics Alone Sufficient to Validate Modelled Flood Extent Quality? : A Study on Three Swedish Rivers Using Different Digital Elevation Model Resolutions
- 2019
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Ingår i: Mathematical problems in engineering (Print). - : Hindawi Publishing Corporation. - 1024-123X .- 1563-5147. ; 2019
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Tidskriftsartikel (refereegranskat)abstract
- Hydraulic modelling is now, at increasing rates, used all over the world to provide flood risk maps for spatial planning, flood insurance, etc. This puts heavy pressure on the modellers and analysts to not only produce the maps but also information on the accuracy and uncertainty of these maps. A common means to deliver this is through performance measures or feature statistics. These look at the global agreement between the modelled flood area and the reference flood that is used. Previous studies have shown that the feature agreement statistics do not differ much between models that have been based on digital elevation models (DEMs) of different resolutions, which is somewhat surprising since most researchers agree that high-resolution DEMs are to be preferred over poor resolution DEMs. Hence, the aim of this study was to look into how and under which conditions the different feature agreement statistics differ, in order to see when the full potential of high-resolution DEMs can be utilised. The results show that although poor resolution DEMs might produce high feature agreement scores (around F > 0.80), they may fail to provide good flood extent estimations locally, particularly when the terrain is flat. Therefore, when high-resolution DEMs (1 to 5 m) are used, it is important to carefully calibrate the models by the use of the roughness parameter. Furthermore, to get better estimates on the accuracy of the models, other performance measures such as distance disparities should be considered.
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