| 1. |
- 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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| 2. |
- Hentati-Sundberg, Jonas, et al.
(författare)
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Seabird surveillance: combining CCTV and artificial intelligence for monitoring and research
- 2023
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Ingår i: Remote Sensing in Ecology and Conservation. - : Wiley. - 2056-3485. ; 9:4, s. 568-581
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Tidskriftsartikel (refereegranskat)abstract
- Ecological research and monitoring need to be able to rapidly convey information that can form the basis of scientifically sound management. Automated sensor systems, especially if combined with artificial intelligence, can contribute to such rapid high-resolution data retrieval. Here, we explore the prospects of automated methods to generate insights for seabirds, which are often monitored for their high conservation value and for being sentinels for marine ecosystem changes. We have developed a system of video surveillance combined with automated image processing, which we apply to common murres Uria aalge. The system uses a deep learning algorithm for object detection (YOLOv5) that has been trained on annotated images of adult birds, chicks and eggs, and outputs time, location, size and confidence level of all detections, frame-by-frame, in the supplied video material. A total of 144 million bird detections were generated from a breeding cliff over three complete breeding seasons (2019–2021). We demonstrate how object detection can be used to accurately monitor breeding phenology and chick growth. Our automated monitoring approach can also identify and quantify rare events that are easily missed in traditional monitoring, such as disturbances from predators. Further, combining automated video analysis with continuous measurements from a temperature logger allows us to study impacts of heat waves on nest attendance in high detail. Our automated system thus produces comparable, and in several cases significantly more detailed, data than those generated from observational field studies. By running in real time on the camera streams, it has the potential to supply researchers and managers with high-resolution up-to-date information on seabird population status. We describe how the system can be modified to fit various types of ecological research and monitoring goals and thereby provide up-to-date support for conservation and ecosystem management.
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| 3. |
- Andersson, Kjell, 1956-2014, et al.
(författare)
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Limited GIS skills hamper spatial planning for green infrastructures in Sweden
- 2022
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Ingår i: Geografiska Notiser. - : Geografilärarnas Riksförening. - 0016-724X. ; 80:1, s. 16-35
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The term green infrastructure captures the need to conserve biodiversity and to sustain landscapes’ different ecosystem services. Maintaining green infrastructures through protected areas, management and landscape restoration requires knowledge in geography, spatial data about biophysical, anthropogenic and immaterial values, spatial comprehensive planning, and thus geographical information systems (GIS). To understand land use planning practices and planning education regarding GIS in Sweden we interviewed 43 planners and reviewed 20 planning education programmes. All planners used GIS to look at data but did not carry out spatial analyses of land covers. BSc programmes included more GIS than MSc programmes but very few taught analyses for spatial planning. As key spatial planning actors, municipalities’ barriers and bridges for improved GIS use for collaborative learning about green infrastructures are discussed. A concluding section presents examples of how GIS can support spatial planning for green infrastructures.
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| 4. |
- Leistner, Theresa, 1996, et al.
(författare)
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COMPARISON OF TOWER-BASED AND SATELLITE L- AND C-BAND RADAR BACKSCATTER FROM A BOREAL FOREST
- 2023
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Ingår i: IGARSS 2023 - 2023 IEEE INTERNATIONAL GEOSCIENCE AND REMOTE SENSING SYMPOSIUM. - 2153-6996. - 9798350320107 ; , s. 8319-8322
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Konferensbidrag (refereegranskat)abstract
- In this study, spaceborne SAR observations were compared to the tower-based radar observations of a hemiboreal forest site in southern Sweden. BorealScat radar tower observations at L- and C-band are verified using Sentinel-1 and ALOS-2 PALSAR-2 products. For L-band, a 14-month backscatter time series was produced. For C-band, a 3.5 year backscatter time series that includes tree deaths due to a bark beetle infestation was produced. Tomographic capabilities of the tower-based BorealScat allowed both canopy-only and full forest backscatter to be analyzed. For a healthy forest, the agreement of tower-based and spaceborne SAR observations was within 0.9 dB for C-band and within 0.6 dB for L-band. Sentinel-1 backscatter was found to be insensitive to tree deaths, whereas variations were clearly visible in the tomographic tower-based backscatter. These results show that tower-based radar observations agree with those of spaceborne SARs and can be used to understand their shortcomings and identify new mission needs.
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| 5. |
- Jin, Hongxiao, et al.
(författare)
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Drone-Based Hyperspectral and Thermal Imagery for Quantifying Upland Rice Productivity and Water Use Efficiency after Biochar Application
- 2021
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Ingår i: Remote Sensing. - : MDPI AG. - 2072-4292. ; 13:10
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Tidskriftsartikel (refereegranskat)abstract
- Miniature hyperspectral and thermal cameras onboard lightweight unmanned aerial vehicles (UAV) bring new opportunities for monitoring land surface variables at unprecedented fine spatial resolution with acceptable accuracy. This research applies hyperspectral and thermal imagery from a drone to quantify upland rice productivity and water use efficiency (WUE) after biochar application in Costa Rica. The field flights were conducted over two experimental groups with bamboo biochar (BC1) and sugarcane biochar (BC2) amendments and one control (C) group without biochar application. Rice canopy biophysical variables were estimated by inverting a canopy radiative transfer model on hyperspectral reflectance. Variations in gross primary productivity (GPP) and WUE across treatments were estimated using light-use efficiency and WUE models respectively from the normalized difference vegetation index (NDVI), canopy chlorophyll content (CCC), and evapotranspiration rate. We found that GPP was increased by 41.9 +/- 3.4% in BC1 and 17.5 +/- 3.4% in BC2 versus C, which may be explained by higher soil moisture after biochar application, and consequently significantly higher WUEs by 40.8 +/- 3.5% in BC1 and 13.4 +/- 3.5% in BC2 compared to C. This study demonstrated the use of hyperspectral and thermal imagery from a drone to quantify biochar effects on dry cropland by integrating ground measurements and physical models.
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| 6. |
- Bennet, Patrik, 1995, et al.
(författare)
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Diurnal Cycles of L-Band Tomographic SAR Backscatter in a Boreal Forest During Summer: Observations by the Borealscat Tower Radar
- 2023
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Ingår i: International Geoscience and Remote Sensing Symposium (IGARSS). ; 2023-July, s. 2195-2198
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Konferensbidrag (refereegranskat)abstract
- The BorealScat tower radar experiment, in Remningstorp, Sweden, acquired tomographic L-band backscatter time series over a boreal forest stand consisting of Norway spruce (Picea abies). Data from summer 2018 is analysed in this study, where diurnal cycles with variations up to more than 1 dB are identified for HH and VV polarizations. The HH cycle has its minimum at night, its maximum at noon and mainly occurs in the middle layers of the forest. Conversely, the VV cycle has its maximum at night, its minimum at noon and is most apparent in the upper and lower forest layers, especially during June and July. The cycles are compared with vapour-pressure deficit (VPD), an indicator of favourable transpiration conditions, and they are seen to co-vary closely. The VV cycle compares well to that seen for P-band in a previous study and is speculated to originate from stem water content variations. The HH cycle cannot be directly connected to stem water content, but is indicated to follow a currently unknown transpiration related phenomena.
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| 7. |
- Darvishi, Mehdi, et al.
(författare)
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InSAR-based Ground Motion Service of Sweden: evaluation and benefit analysis of a nationwide InSAR service
- 2022
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Konferensbidrag (refereegranskat)abstract
- Space-geodetic techniques such as Global Navigation Satellite Systems (GNSS) and Syntenic Aperture Radar interferometry (InSAR) are powerful tools to measure and monitor ground surface motion. InSAR has widely been used for the detection and quantification of slow mass movements over the past three decades mainly at the local and regional scales. The high performance and millimeter-level measurement accuracy of radar satellite to provide a dense deformation map at different spatial and temporal resolutions are the key factors to think of using SAR data and InSAR technique as an efficient tool for geohazards motoring system at the nationwide scale.Sweden has recently joined to the countries having InSAR Ground Motion Service (GMS) at a nationwide scale. The InSAR service of Sweden, which will soon be freely available for users, provides the displacement time-series of measurement points for the entire country. The Swedish GMS project was started last year and is an ongoing collaboration between the Geological Survey of Norway (NGU) and several Swedish organizations (led by the Swedish National Space Agency (SNSA)). The InSAR-based GMS of Sweden has been generated by NGU using Sentinel-1 data (2015–2020) and the Persistent Scatterer Interferometry (PSI) technique. The web-based GMS of Sweden consists of ~1,5 billion time-series measurement points obtained from both descending and ascending satellite orbital modes.Currently, the Swedish GMS is under evaluation and validation phase and the given plan has been designed to assess the quality or validate the GMS products. We plan to conduct the data validation through two main phases: 1) a cross-comparison between InSAR measurement points and ancillary data such as GNSS, Corner Reflectors (CR), Electronic Corner Reflectors (ECR) and leveling data, and 2) assessment of tropospheric and ionospheric effects on InSAR measurement points. Specifically, we will evaluate different approaches and data for the InSAR tropospheric corrections, such as Very-Long-Baseline Interferometry (VLBI), Water Vapour Radiometry (WVR), and GNSS data at the Onsala Space Observatory (OSO).In the first phase of validation, leveling data collected in Gothenburg and Stockholm cities, mainly over the residential areas and public transport infrastructures compared to the corresponding InSAR measurements points (vertically converted) for a five-year period. The initial results present a high correlation between two sets of the vertical displacements. The same procedure will be performed for the Kiruna city where the mining activities resulted in adrastic urban land subsidence. Since the CRs and ECRs have recently been installed in different parts of Sweden, we do not have them as PS points in the current version of the GMS. Therefore, those CR-based measurement points will be used in future accuracy assessments. In the second phase, we investigated the effects of phase delay induced by troposphere on displacement time-series using two approaches, i.e., time-space filtering and using external data (e.g., atmospheric reanalysis data, GNSS, VLBI and Water Vapor Radiometer (WVR)). Recently, European GMS (EGMS) has been released and the Ortho displacement map is now available for users freely. We also evaluated and compared the EGMS-Ortho displacement map with our independent InSAR processing and GNSS data over the Kiruna.As the InSAR-based GMS can be used to monitor and identify the potential risk of geo-related hazards in Sweden, the society will directly benefit from the outcomes of this project. This open access product will help the stakeholders with decision support for prioritization of risk-reducing measures, and identification of the need for further investigations for areas in danger. The service could also assist municipalities and county administrative boards to have an update information regarding urban areas which are more prone to land subsidence and disruption urban infrastructure.
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| 8. |
- Monteith, Albert, 1990
(författare)
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Temporal Characteristics of Boreal Forest Radar Measurements
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Radar observations of forests are sensitive to seasonal changes, meteorological variables and variations in soil and tree water content. These phenomena cause temporal variations in radar measurements, limiting the accuracy of tree height and biomass estimates using radar data. The temporal characteristics of radar measurements of forests, especially boreal forests, are not well understood. To fill this knowledge gap, a tower-based radar experiment was established for studying temporal variations in radar measurements of a boreal forest site in southern Sweden. The work in this thesis involves the design and implementation of the experiment and the analysis of data acquired. The instrument allowed radar signatures from the forest to be monitored over timescales ranging from less than a second to years. A purpose-built, 50 m high tower was equipped with 30 antennas for tomographic imaging at microwave frequencies of P-band (420-450 MHz), L-band (1240-1375 MHz) and C-band (5250-5570 MHz) for multiple polarisation combinations. Parallel measurements using a 20-port vector network analyser resulted in significantly shorter measurement times and better tomographic image quality than previous tower-based radars. A new method was developed for suppressing mutual antenna coupling without affecting the range resolution. Algorithms were developed for compensating for phase errors using an array radar and for correcting for pixel-variant impulse responses in tomographic images. Time series results showed large freeze/thaw backscatter variations due to freezing moisture in trees. P-band canopy backscatter variations of up to 10 dB occurred near instantaneously as the air temperature crossed 0⁰C, with ground backscatter responding over longer timescales. During nonfrozen conditions, the canopy backscatter was very stable with time. Evidence of backscatter variations due to tree water content were observed during hot summer periods only. A high vapour pressure deficit and strong winds increased the rate of transpiration fast enough to reduce the tree water content, which was visible as 0.5-2 dB backscatter drops during the day. Ground backscatter for cross-polarised observations increased during strong winds due to bending tree stems. Significant temporal decorrelation was only seen at P-band during freezing, thawing and strong winds. Suitable conditions for repeat-pass L-band interferometry were only seen during the summer. C-band temporal coherence was high over timescales of seconds and occasionally for several hours for night-time observations during the summer. Decorrelation coinciding with high transpiration rates was observed at L- and C-band, suggesting sensitivity to tree water dynamics. The observations from this experiment are important for understanding, modelling and mitigating temporal variations in radar observables in forest parameter estimation algorithms. The results also are also useful in the design of spaceborne synthetic aperture radar missions with interferometric and tomographic capabilities. The results motivate the implementation of single-pass interferometric synthetic aperture radars for forest applications at P-, L- and C-band.
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| 9. |
- Natalino Da Silva, Carlos, 1987, et al.
(författare)
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Scalable and Efficient Pipeline for ML-based Optical Network Monitoring
- 2023
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Ingår i: 2023 Optical Fiber Communications Conference and Exhibition, OFC 2023 - Proceedings.
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Konferensbidrag (refereegranskat)abstract
- We demonstrate a scalable processing of OPM data using ML to detect anomalies in optical services at run time. A dashboard will show operational SDN controller metrics, raw OPM data, and the ML assessment results.
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| 10. |
- Shami, Siavash, et al.
(författare)
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Assessments of ground subsidence along the railway in the Kashan plain, Iran, using Sentinel-1 data and NSBAS algorithm
- 2022
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Ingår i: International Journal of Applied Earth Observation and Geoinformation. - : Elsevier. - 1569-8432 .- 1872-826X. ; 112
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Tidskriftsartikel (refereegranskat)abstract
- The 110-kilometer-long Qom-Kashan railway is one of the busiest lines in Iran, passing through the Kashan plain. The majority of Iran's plains have subsided in recent years as a result of uncontrolled groundwater extraction, and the Kashan plain is no exception. In this study, ground surface displacement in the Kashan plain region and its impact on the railway were investigated using New Small Baseline Subset (NSBAS) in up-down and east–west directions using descending and ascending Sentinel-1 data collected between 2015 and 2021. Our results indicate that the Kashan plain is subsiding more than 90 mm/year. The study of the local areas around the railway which passes through the study area revealed that the rate of vertical velocity in some locations reaches –23 mm/year, while the rate of east–west velocity is insignificant and is approximately ±2 mm/year. Additionally, a method for analyzing the railway's stability based on longitudinal profiles along the railway is presented. Our findings suggest that more than 60% of the railway line is subject to variable amounts of subsidence. Additionally, a region of approximately one kilometer of the railway has been classified as a risk zone due to relatively fast local deformation. After examining the effect of various factors, it was determined that uncontrolled groundwater extraction in agricultural areas contributed to the subsidence in this area. Our results show that the presented stability control approach in this study is highly reliable for creating hazard profiles for linear structures, such as railways.
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