| 1. |
- Earon, Robert, et al.
(författare)
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Groundwater Resources Potential in Hard Rock Terrain : A Multivariate Approach
- 2014
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Ingår i: Ground Water. - : John Wiley & Sons. - 0017-467X .- 1745-6584.
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Tidskriftsartikel (refereegranskat)abstract
- Groundwater resources are limited and difficult to predict in crystalline bedrock due to heterogeneity and anisotropy in rock fracture systems. Municipal-level governments often lack the resources for traditional hydrogeological tests when planning for sustainable use of water resources. A new methodology for assessing groundwater resources potential (GRP) based on geological and topographical factors using principal component analysis (PCA) and analysis of variance (ANOVA) was developed and tested. ANOVA results demonstrated statistically significant differences in classed variable groups as well as in classed GRP scores with regard to hydrogeological indicators, such as specific capacity (SC) and transmissivity. Results of PCA were used to govern the weight of the variables used in the prediction maps. GRP scores were able to identify 79% of wells in a verification dataset, which had SC values less than the total dataset median. GRP values showed statistically significant correlations using both parametric (using transformed datasets) and non-parametric methods. The method shows promise for municipal or regional level planning in crystalline terrains with high levels of heterogeneity and anisotropy as a hydrogeologically and statistically based tool to assist in assessing groundwater resources. The methodology is executed in a geographic information systems environment, and uses often readily available data, such as geological maps, feature maps and topography, and thus does not require expensive and time-consuming aquifer tests.
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| 2. |
- Buckland, Philip I., 1973-, et al.
(författare)
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The Swedish Transport Administration’s Toolbox and its Potential in Archaeological and Cultural Heritage Survey : Including a brief review of remote sensing, prospection and geodata analysis methods for archaeology and cultural heritage
- 2018
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report provides an overview of the main remote sensing methods and geodata types used in archaeological prospection and cultural heritage survey. Based on a literature review, it provides an initial survey of the state of the art nationally and internationally, followed by details on the potential usage of different methods in a Swedish context. The details include pros and cons of methods as well as information on considerations that should be taken into account when applying the methods in different situations. Examples are provided where relevant to explain specific details or illustrate important points. Particular attention has been paid to laser scanning (LiDAR) data due to its increasing prevalence and prominence in landscape and archaeological surveys.The report continues with a preliminary evaluation of the possibilities for using data provided by Swedish Transport Administration (Trafikverket), obtained for other stages of the planning process, in archaeological and cultural heritage work. Specifically, the report looks at a number of geodata types obtained from The Geological Survey of Sweden (Sveriges geologiska undersökning/SGU), a nature conservation survey in report form, a ground penetrating radar technical report, terrain laser scanning (LiDAR) and orthophotos (geometrically corrected aerial photographs). The SGU geodata consist of a number of Geographical Information System (GIS) layers describing bedrock and soil types, and the nature conservation survey included accompanying, but incomplete, GIS data. This section consists of concise descriptions of the potential of each group of GIS layers or data, and is complemented by brief, bullet point summaries along with additional technical information in Appendix 1. Comments have been made where additional, related, data sources would be useful. Swedish terms are included in parenthesis where the term differs significantly from the English equivalent.A final summary provides a compact overview of the main points of the report before providing some conclusions and ideas for further work. This is in turn followed by a list of ideas for enhancing the efficiency with which the types of data discussed can be used in infrastructure projects which have a potential to impact on archaeology/cultural heritage.References are provided to support important or potentially contentious points or where further reading or research would be advised for a more comprehensive understanding of relevant issues.
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| 3. |
- 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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| 4. |
- Arellano, Santiago, 1981
(författare)
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Studies of Volcanic Plumes with Remote Spectroscopic Sensing Techniques -DOAS and FTIR measurements on volcanoes of the Network for Observation of Volcanic and Atmospheric Change-
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Volcanism is a rich geodynamical process, closely linked to the origin and ongoing evolution of the lithosphere, atmosphere, hydrosphere and biosphere. Humans have benefited from the resources provided by volcanoes but also been threatened by the dangers of volcanic eruptions, which accurate prediction remains elusive. This is partly due to the inherent complexity of volcanic systems and partly because of the difficulty of conducting key observations to characterize them. In particular, since the segregation and escape of magmatic volatiles are essential mechanisms behind volcanic eruptions, monitoring the intensity and composition of the resulting emissions in the atmosphere is essential to characterize the state of volcanic activity; however, their direct measurement is not always feasible.Remote spectroscopic sensing, whereby gas species can be quantified by their spectral signatures in electromagnetic radiation gathered at a prudent distance from the plume, offers the possibility to conduct reliable and sustainable monitoring of volcanic emissions. To expand the remote sensing capabilities of volcanological observatories the Network for Observation of Volcanic and Atmospheric Change (NOVAC) was established in 2005. The central theme of this thesis is the acquisition, analysis and interpretation of measurements of volcanic gas emissions on volcanoes of NOVAC. Measurements of the mass flow rate of SO2 and the molar ratios of SO2 against BrO and HCl were obtained by scanning-Differential Optical Absorption Spectroscopy (DOAS) of scattered solar ultraviolet radiation and by Fourier-Transform Spectroscopy (FTIR) of direct solar infrared radiation. The uncertainty of the measurements is characterized and methods for combining observations from different sensors implemented. Statistical and physical models of degassing are proposed for selected volcanoes of the network. The resulting time-series of emission on 16 volcanoes is one of the more detailed compilations of volcanic degassing in the last decade, particularly from passive emissions which are difficult to detect from satellite platforms. This work aims at advancing our knowledge of volcanic eruptions for a better mitigation of their risks.
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| 5. |
- Hammar, Arvid, 1986, et al.
(författare)
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Optical Tolerance Analysis of the Multi-Beam Limb Viewing Instrument STEAMR
- 2014
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Ingår i: IEEE Transactions on Terahertz Science and Technology. - 2156-342X .- 2156-3446. ; 4:6, s. 714-721
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Tidskriftsartikel (refereegranskat)abstract
- We report on an optical tolerance analysis of the submillimeter atmospheric multi-beam limb sounder STEAMR. Physical optics and ray-tracing methods were used to quantify and separate errors in beam pointing and distortion due to reflector misalignment and primary reflector surface deforma-tions. Simulations were performed concurrently with the man-ufacturing of a multi-beam demonstrator of the relay optical system which shapes and images the beams to their corresponding receiver feed horns. Results from Monte-Carlo simulations show that the inserts used for reflector mounting should be positioned with an overall accuracy better than 100 µm (~1/10 wavelength). Analyses of primary reflector surface deformations show that a deviation of magnitude 100 µm can be tolerable before deployment, whereas the corresponding variations should be less than 30 µm during operation. The most sensitive optical elements in terms of misalignments are found near the focal plane. This localized sensitivity is attributed to the off-axis nature of the beams at this location. Post-assembly mechanical measurements of the reflectors in the demonstrator show that alignment better than 50 µm could be obtained.
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| 6. |
- Brandt, S. Anders, 1970-, et al.
(författare)
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Importance of river bank and floodplain slopes on the accuracy of flood inundation mapping
- 2012
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Ingår i: River Flow 2012. - Leiden, The Netherlands : CRC Press / Balkema (Taylor & Francis). - 9780415621298 - 9780203076354 - 9781466575523 ; , s. 1015-1020
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Konferensbidrag (refereegranskat)abstract
- Effective flood assessment and management depend on accurate models of flood events, which in turn are strongly affected by the quality of digital elevation models (DEMs). In this study, HEC-RAS was used to route one specificwater discharge through the main channel of the Eskilstuna River, Sweden. DEMs with various resolutions and accuracies were used to model the inundation. The results showed a strong positive relationship between the quality of theDEMand the extent of the inundation. However, evenDEMswith the highest resolution produced inaccuracies. In another case study, the Testebo River, the model settings could be calibrated, thanks to a surveyed old inundation event. However, even with the calibration efforts, the resulting inundation extents showed varying degrees of deviation from the surveyed flood boundaries. Therefore, it becomes clear that not only does the resolution of the DEM impact the quality of the results; also, the floodplain slope perpendicular to the river flow will impact the modelling accuracy. Flatter areas exhibited the greatest predictive uncertainties regardless of the DEM’s resolution. For perfectly flat areas, uncertainty becomes infinite.
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| 7. |
- Buckland, Paul, et al.
(författare)
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Edlington Wood : using Lidar to put ancient fields and old excavations into their contemporary landscape
- 2020
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Ingår i: Transactions of the Hunter Archaeological Society. - Sheffield : The Hunter Archaeological Society. - 0966-2251. ; 29, s. 84-101
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Tidskriftsartikel (refereegranskat)abstract
- The Roman sites in Edlington Wood, three miles west-south-west of Doncaster, South Yorkshire, first came to wider notice as a result of finds by the woodman in the 1930s and the material was of sufficient interest for Philip Corder to use it as the basis for a paper in a festschrift to O. G. S. Crawford. Most of these finds and later material were deposited in Doncaster Museum, although others went to the owners and local metal detectorists. In 1970 a threat of quarrying led to a detailed survey of the site by the Royal Commission on Historical Monuments and limited excavation on one site. Two large areas within the Wood were cleared but remain as improved grassland. The recent availability of Lidar imagery allows the occupation sites and fragments of field system located by ground survey to be placed in a broader context of small rectangular fields and some attempt at a landscape chronology to be made. The cultivation of the fields in a system of cord rig is discussed.
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| 8. |
- Aldenhoff, Wiebke, 1985, et al.
(författare)
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Comparison of ice/water classification in Fram Strait from C- and L-band SAR imagery
- 2018
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Ingår i: Annals of Glaciology. - : Cambridge University Press (CUP). - 0260-3055 .- 1727-5644. ; 59:76pt2, s. 112-123
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Tidskriftsartikel (refereegranskat)abstract
- In this paper an algorithm for ice/water classification of C- and L-band dual polarization synthetic aperture radar data is presented. A comparison of the two different frequencies is made in order to investigate the potential to improve classification results with multi-frequency data. The algorithm is based on backscatter intensities in co- and cross-polarization and autocorrelation as a texture feature. The mapping between image features and ice/water classification is made with a neural network. Accurate ice/water maps for both frequencies are produced by the algorithm and the results of two frequencies generally agree very well. Differences are found in the marginal ice zone, where the time difference between acquisitions causes motion of the ice pack. C-band reliably reproduces the outline of the ice edge, while L-band has its strengths for thin ice/calm water areas within the icepack. The classification shows good agreement with ice/water maps derived from met.no ice-charts and radiometer data from AMSR-2. Variations are found in the marginal ice zone where the generalization of the ice charts and lower accuracy of ice concentration from radiometer data introduce deviations. Usage of high-resolution dual frequency data could be beneficial for improving ice cover information for navigation and modelling.
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| 9. |
- Junttila, Sofia, et al.
(författare)
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Upscaling Northern Peatland CO2 Fluxes Using Satellite Remote Sensing Data
- 2021
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Ingår i: Remote Sensing. - : MDPI AG. - 2072-4292. ; 13:4
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Tidskriftsartikel (refereegranskat)abstract
- Peatlands play an important role in the global carbon cycle as they contain a large soil carbon stock. However, current climate change could potentially shift peatlands from being carbon sinks to carbon sources. Remote sensing methods provide an opportunity to monitor carbon dioxide (CO2) exchange in peatland ecosystems at large scales under these changing conditions. In this study, we developed empirical models of the CO2 balance (net ecosystem exchange, NEE), gross primary production (GPP), and ecosystem respiration (ER) that could be used for upscaling CO2 fluxes with remotely sensed data. Two to three years of eddy covariance (EC) data from five peatlands in Sweden and Finland were compared to modelled NEE, GPP and ER based on vegetation indices from 10 m resolution Sentinel-2 MSI and land surface temperature from 1 km resolution MODIS data. To ensure a precise match between the EC data and the Sentinel-2 observations, a footprint model was applied to derive footprint-weighted daily means of the vegetation indices. Average model parameters for all sites were acquired with a leave-one-out-cross-validation procedure. Both the GPP and the ER models gave high agreement with the EC-derived fluxes (R-2 = 0.70 and 0.56, NRMSE = 14% and 15%, respectively). The performance of the NEE model was weaker (average R-2 = 0.36 and NRMSE = 13%). Our findings demonstrate that using optical and thermal satellite sensor data is a feasible method for upscaling the GPP and ER of northern boreal peatlands, although further studies are needed to investigate the sources of the unexplained spatial and temporal variation of the CO2 fluxes.
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| 10. |
- Nickman, Alireza
(författare)
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Road disasters? Modeling and assessment of Swedish roads within crucial climate conditions
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- An efficient maintenance of roads to ensure high accessibility and durability of the transport capacity requires an understanding of how the hydrological response depends on both the road and the landscape characteristics. New methods and data were used to identify and explain interaction between roads and surrounding environment and their influence on hydrologic responses both in watershed scale and road-section scale. In the watershed scale, flood hazard probability was made with reference to the most influential physical catchment descriptors and road characteristics. Additionally, a physical based model was used to estimate the effect of road topography on the hydrological responses of 20 watersheds to storms with different intensities. A simple method was developed and discussed to address flood risk probability in the road-stream crossings concerning the correlation between the quantities of the physical catchment descriptors and occurrence/absence of flooding. The most influential factors in describing the probability of flooding along the roads were topographic wetness index, soil properties, road density and channel slopes. A detailed study of simulated flow duration curves showed differences between the 20 watersheds for three different storms based on topography with and without roads. An increase in peak flow and reduced time to pick occurred with existence of roads and increased storm intensity.In the road-section scale, an uncertainty-based simulation approach was used to identify the most influencing processes in controlling the dynamics of the groundwater level. A model (CoupModel) set up with four different geological stratifications was made to model two positions in a slope upstream of a road with drainage pipes and ditches. Results from the simulations indicate the significance of precipitation rate, road drainage and position in hillslope, and soil properties and stratifications in controlling groundwater levels. The same model was also applied to simulate soil moisture and temperature dynamics in two road sections by using groundwater and climate data. Porous media properties were obtained as statistical distribution function that provided the best performance of moisture and temperature dynamic in the road layers and underlying soil.
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