| 1. |
- 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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| 2. |
- 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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| 3. |
- Aldenhoff, Wiebke, 1985, et al.
(författare)
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COMPARISON OF SENTINEL-1 SAR AND SENTINEL-3 ALTIMETRY DATA FOR SEA ICE TYPE DISCRIMINATION
- 2019
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Ingår i: IGARSS 2019 - 2019 IEEE International Geoscience and Remote Sensing Symposium. - 9781538691540
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this paper near co-incidental Sentinel-1 C-band SAR imagery and Sentinel-3 SRAL Ku-band altimeter data are compared for their capabilities of sea ice type discrimination. Knowledge of sea ice type is important for climate research and safety in Arctic offshore operations. First-year ice is characterised by a low SAR backscatter intensity in both HH and HV polarisation compared to multi-year ice, while the altimeter waveform parameters show high pulse peakiness and peak power compared to multi-year ice. Thus SAR imagery and altimetry can principally discriminate different ice types. The complexity of the backscattered radar signal however impedes a clear separation of the two types for all cases. Cross comparison of the two sensors offers an opportunity of high resolution validation data, which is often lacking for sea ice studies.
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| 4. |
- 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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| 5. |
- Strandberg, Joakim, 1991, et al.
(författare)
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Improving GNSS-R sea level determination through inverse modeling of SNR data
- 2016
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Ingår i: Radio Science. - 0048-6604 .- 1944-799X. ; 51:8, s. 1286-1296
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a new method for retrieving sea surface heights from Global Navigation Satellite Systems reflectometry (GNSS-R) data by inverse modeling of SNR observations from a single geodetic receiver. The method relies on a B-spline representation of the temporal sea level variations in order to account for its continuity. The corresponding B-spline coefficients are determined through a nonlinear least squares fit to the SNR data, and a consistent choice of model parameters enables the combination of multiple GNSS in a single inversion process. This leads to a clear increase in precision of the sea level retrievals which can be attributed to a better spatial and temporal sampling of the reflecting surface. Tests with data from two different coastal GNSS sites and comparison with colocated tide gauges show a significant increase in precision when compared to previously used methods, reaching standard deviations of 1.4 cm at Onsala, Sweden, and 3.1 cm at Spring Bay, Tasmania.
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| 6. |
- Forsman, Mona, et al.
(författare)
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Estimation of Tree Stem Attributes using Terrestrial Photogrammetry with a Camera Rig
- 2016
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Ingår i: Forests. - Basel, Switzerland : MDPI (Multidisciplinary Digital Publishing Institute). - 1999-4907. ; 7:3
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Tidskriftsartikel (refereegranskat)abstract
- We propose a novel photogrammetric method for field plot inventory, designed for simplicity and time efficiency on-site. A prototype multi-camera rig was used to acquire images from field plot centers in multiple directions. The acquisition time on-site was less than two minutes. From each view, a point cloud was generated using a novel, rig-based matching of detected SIFT keypoints. Stems were detected in the merged point cloud, and their positions and diameters were estimated. The method was evaluated on 25 hemi-boreal forest plots of a 10-m radius. Due to difficult lighting conditions and faulty hardware, imagery from only six field plots was processed. The method performed best on three plots with clearly visible stems with a 76% detection rate and 0% commission. Dieameters could be estimated for 40% of the stems with an RMSE of 2.8-9.5 cm. The results are comparable to other camera-based methods evaluated in a similar manner. The results are inferior to TLS-based methods. However, our method is easily extended to multiple station image schemas, something that could significantly improve the results while retaining low commission errors and time on-site. Furthermore, with smaller hardware, we believe this could be a useful technique for measuring stem attributes in the forest.
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| 7. |
- Fornieles-Callejon, J., et al.
(författare)
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Extremely low frequency band station for natural electromagnetic noise measurement
- 2015
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Ingår i: Radio Science. - 0048-6604 .- 1944-799X. ; 50:3, s. 191-201
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Tidskriftsartikel (refereegranskat)abstract
- A new permanent ELF measurement station has been deployed in Sierra Nevada, Spain. It is composed of two magnetometers, oriented NS and EW, respectively. At 10 Hz, their sensitivity is 19 V/pT and the signal-to-noise ratio (SNR) is 28 dB for a time-varying signal of 1 pT, the expected field amplitude in Sierra Nevada. The station operates for frequencies below 24 Hz. The magnetometers, together with their corresponding electronics, have been specifically designed to achieve such an SNR for small signals. They are based on high-resolution search coils with ferromagnetic core and 10(6) turns, operating in limited geometry configuration. Different system noise sources are considered, and a study of the SNR is also included. Finally, some initial Schumann resonance measurements are presented in order to validate the performance of the measurement station, including 1 h length spectra, daily variations of resonance amplitudes and frequencies for the different seasons, and a 3 day spectrogram.
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| 8. |
- Brandt, S. Anders, 1970-, et al.
(författare)
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Visualising DEM-related flood-map uncertainties using a disparity-distance equation algorithm
- 2016
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Ingår i: IAHS-AISH Proceedings and Reports. - Göttingen : Copernicus Publications on behalf of International Association of Hydrological Sciences (IAHS). ; , s. 153-159
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Konferensbidrag (refereegranskat)abstract
- The apparent absoluteness of information presented by crisp-delineated flood boundaries can lead tomisconceptions among planners about the inherent uncertainties associated in generated flood maps. Even mapsbased on hydraulic modelling using the highest-resolution digital elevation models (DEMs), and calibrated withthe most optimal Manning’s roughness (n) coefficients, are susceptible to errors when compared to actual floodboundaries, specifically in flat areas. Therefore, the inaccuracies in inundation extents, brought about by thecharacteristics of the slope perpendicular to the flow direction of the river, have to be accounted for. Instead ofusing the typical Monte Carlo simulation and probabilistic methods for uncertainty quantification, an empiricalbaseddisparity-distance equation that considers the effects of both the DEM resolution and slope was used tocreate prediction-uncertainty zones around the resulting inundation extents of a one-dimensional (1-D) hydraulicmodel. The equation was originally derived for the Eskilstuna River where flood maps, based on DEM dataof different resolutions, were evaluated for the slope-disparity relationship. To assess whether the equation isapplicable to another river with different characteristics, modelled inundation extents from the Testebo Riverwere utilised and tested with the equation. By using the cross-sectional locations, water surface elevations, andDEM, uncertainty zones around the original inundation boundary line can be produced for different confidences.The results show that (1) the proposed method is useful both for estimating and directly visualising modelinaccuracies caused by the combined effects of slope and DEM resolution, and (2) the DEM-related uncertaintiesalone do not account for the total inaccuracy of the derived flood map. Decision-makers can apply it to alreadyexisting flood maps, thereby recapitulating and re-analysing the inundation boundaries and the areas that areuncertain. Hence, more comprehensive flood information can be provided when determining locations whereextra precautions are needed. Yet, when applied, users must also be aware that there are other factors that caninfluence the extent of the delineated flood boundary.
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| 9. |
- Karlson, Martin, et al.
(författare)
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Assessing the potential of multi-seasonal WorldView-2 imagery for mapping West African agroforestry tree species
- 2016
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Ingår i: International Journal of Applied Earth Observation and Geoinformation. - : Elsevier BV. - 1569-8432 .- 0303-2434 .- 1872-826X. ; 50:August, s. 80-88
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Tidskriftsartikel (refereegranskat)abstract
- High resolution satellite systems enable efficient and detailed mapping of tree cover, with high potential to support both natural resource monitoring and ecological research. This study investigates the capability of multi-seasonal WorldView-2 imagery to map five dominant tree species at the individual tree crown level in a parkland landscape in central Burkina Faso. The Random Forest algorithm is used for object based tree species classification and for assessing the relative importance of WorldView-2 predictors. The classification accuracies from using wet season, dry season and multi-seasonal datasets are compared to gain insights about the optimal timing for image acquisition. The multi-seasonal dataset produced the most accurate classifications, with an overall accuracy (OA) of 83.4%. For classifications based on single date imagery, the dry season (OA = 78.4%) proved to be more suitable than the wet season (OA = 68.1%). The predictors that contributed most to the classification success were based on the red edge band and visible wavelengths, in particular green and yellow. It was therefore concluded that WorldView- 2, with its unique band configuration, represents a suitable data source for tree species mapping in West African parklands. These results are particularly promising when considering the recently launched WorldView-3, which provides data both at higher spatial and spectral resolution, including shortwave infrared bands.
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| 10. |
- Englund, Oskar, 1982, et al.
(författare)
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A new high-resolution nationwide aboveground carbon map for Brazil
- 2017
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Ingår i: Geo: Geography and Environment. - : Wiley. - 2054-4049. ; 4:2, s. e00045-
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Tidskriftsartikel (refereegranskat)abstract
- Brazil is home to the largest tracts of tropical vegetation in the world, harbouring high levels of biodiversity and carbon. Several biomass maps have been produced for Brazil, using different approaches and methods, and for different purposes. These maps have been used to estimate historic, recent, and future carbon emissions from land use change (LUC). It can be difficult to determine which map to use for what purpose. The implications of using an unsuitable map can be significant, since the maps have large differences, both in terms of total carbon storage and its spatial distribution. This paper presents comparisons of Brazil’s new ‘official’ carbon map; that is, the map used in the third national communication to the UNFCCC in 2016, with the former official map, and four carbon maps from the scientific literature. General strengths and weaknesses of the different maps are identified, including their suitability for different types of studies. No carbon map was found suitable for studies concerned with existing land use/cover (LULC) and LUC outside of existing forests, partly because they do not represent the current LULC sufficiently well, and partly because they generally overestimate carbon values for agricultural land. A new map of aboveground carbon is presented, which was created based on data from existing maps and an up- to-date LULC map. This new map reflects current LULC, has high accuracy and resolution (50 m), and a national coverage. It can be a useful alternative for scientific studies and policy initiatives concerned with existing LULC and LUC outside of existing forests, especially at local scales when high resolution is necessary, and/or outside the Amazon biome. We identify five ongoing climate policy initiatives in Brazil that can benefit from using this map.
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