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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Utvärdering av fotogrammetrisk datakvalité från drönare : Jämförelse av datamängder från Lantmäteriet i relation till direkt och indirekt georefererat data

Herbertsson, Jessie January 2020 (has links)
Geospatialt data kan samlas in på en mängd olika sätt, där laserskanning och flygfotografering är några av dem. Genom de antal tekniker som möjliggör insamlingen av geospatialt data existerar lösningar såsom användning av Global Navigation Satellite System, Light Detection and Rangning, Structure-from-Motion m.fl. I och med dessa teknologier kan datamängder som höjdmodeller, punktmoln och ortofoton produceras. Inom Sverige finns det en mängd datakällor som kommuner kan använda sig av, där bl.a. Lantmäteriet är en av dem. Då det finns en risk av en fördröjning i uppdatering av data går kommuner runt om i landet potentiellt miste om uppdaterat data. En av de möjliga lösningarna för att få tillgång till uppdaterat data är att kommuner själva samlar in data. I och med denna studie undersöks om drönare är ett lämpligt alternativ till andra datakällor. Vid undersökningen utvärderades skillnader mellan datamängder som var georefererat med markkontrollpunkter och utan i relation till Lantmäteriets data. De datamängder som skapades baserat på drönarens flygbilder varierade i kvalité i kontrast till de inställningar som användes i Agisoft. Genom beräkning av kvadratisk medelavvikelse, differens, punktavstånd och punktäthet identifierades skillnader i kvalité i de skapade datamängder: höjdmodeller, punktmoln och ortofoton. Resultaten av detta visade att data som var georeferat med markkontrollpunkter hade högst lägesnoggrannhet och högre än Lantmäteriets data. Ytterligare hade de skapade datamängder i denna studie högre upplösning (ortofoton & höjdmodeller) samt punktäthet och punktantal (punktmoln). Genom resultaten visar en av slutsatserna i denna studie att lämpligheten för att samla in data på eget bevåg av tillräcklig god kvalité är möjlig och att detaljgraden i relation till Lantmäteriets data är högre / Spatial data can be collected in a variety of ways, where laser scanning and aerial photography are some of them. With the use different technologies such as Global Navigation Satellite System, Light Detection and Ranging, Structure-from-Motion and more, enables the collection of spatial data. With these technologies, datasets such as elevation models, point clouds and orthophotos can be produced. Within Sweden, there are several data sources that municipalities can use, where Lantmäteriet is one of them. Since there is a risk of a delay in updating data, municipalities around the country are potentially losing out on updated data. The possible solutions for accessing updated data is that municipalities themselves collect data. This study will investigate whether drones are a suitable alternative to other data sources. In the survey, differences between data sets that were georeferenced with ground control points and without in relation to data from Lantmäteriet were evaluated. The amounts of data that were created based on the drone's aerial images varied in quality in contrast to the settings used in Agisoft. By calculating root mean square error, difference, point distance and point density, differences in quality were identified in the datasets created: elevation models, point clouds and orthophotos. The results showed that data georeferenced with ground control points had the highest positional accuracy and higher than the data from Lantmäteriet. Further, the datasets created in this study had higher resolution (orthophotos & elevation models) as well as point density and number of points (point clouds). Through the results, one of the conclusions of this study shows that the suitability for collecting data on municipalities own accord of sufficiently good quality is possible and that the degree of detail in relation to data from Lantmäteriet is higher.
22

Mount Meager, a glaciated volcano in a changing cryosphere : hazards and risk challenges / Mount Meager, un volcan glaciaire dans une cryosphère en mutation : dangers et risques

Roberti, Gioachino 24 October 2018 (has links)
Mount Meager est un complexe volcanique glaciaire en British Columbia (Canada). Il est connu pour ses glissements de terrain, dont celui de 2010 étant le plus grand glissement de terrain historique au Canada. Dans cette thèse, nous avons étudié les processus d'instabilités du volcan Mont Meager ainsi que les effets de la déglaciation en cours. Nous avons utilisé une approche pluridisciplinaire, intégrant la cartographie géologique, géomorphologique et structurelle, du terrain et de la télédétection, pour caractériser l'activité glaciaire et les glissements de terrain au Mount Meager. Nous avons utilisé la photogrammétrie Structure from Motion (SfM) et la technologie Lidar pour produire des modèles numériques de terrain, et techniques InSAR pour surveiller le mouvement et la déformation des pentes du volcan. Nous avons appliqué la technique SfM à des photographies aériennes historiques pour documenter les activités des glaciers et des glissements de terrain au Mount Meager. Nous avons discuté un modèle de croissance et d'érosion d'un volcan en période glaciaire et interglaciaire, ainsi que la valeur scientifique et de vulgarisation de la reconstruction topographique 3D. Nous avons décrit les dépôts de glissement de terrain de 2010 à Mount Meager pour interpréter la dynamique de leur mise en place. Le glissement de terrain de 2010 s'est divisé en phases riches en eau et pauvres en eau, ayant des distances d'écoulement différentes et des dépôts distincts. Nous avons analysé des photographies aériennes historiques remontant à 1948, afin de documenter la déformation de la pente avant l'effondrement de 2010. Le glacier situé a proximité du pied de la pente a reculé durant les années précédents la rupture. Cette effondrement a évolué en quatre sous-effondrements, impliquant toute la séquence volcanique et le socle. Nous avons estimé 6 × 106 m3 d'eau dans la pente, ce qui a permis la séparation de la phase frontale riche en eau. Le volume total d'effondrement est 53 ± 3.8 × 106 m3. Nous avons identifié 27 grands (>5×105 m2) flancs instables au Mount Meager et calculé a ~1.3 km3 de récession des glaciers depuis 1987. Le flanc ouest de Plinth Peak et de la vallée de Devastation Creek se sont déplacés de -34±10 mm -36±10 mm, respectivement, dans un période de 24 jours pendant l'été 2016. L’effondrement de ces flancs pourrait avoir un impact important sur les infrastructures et les communautés en aval du volcan. La décompression résultant de l'édifice volcanique après l'effondrement du flanc ouest de Plinth Peak affecterait le champ de contrainte à une profondeur de 6 km et jusqu'à 4 MPa. Cette décompression soudaine pourrait mener des éruptions hydrothermales et magmatiques. Un important glissement de terrain pourrait donc avoir joué un rôle dans le déclenchement de l'éruption de 2360 cal BP. / Mount Meager is a glacier-clad volcanic complex in British Columbia, Canada. It is known for its landslides, of which the 2010 is the largest Canadian historical landslide. In this thesis we investigated slope instability processes at Mount Meager volcano and the effects of ongoing deglaciation. We used a variety of methods including field and remote, geological, geomorphological and structural mapping to characterize glacial and landslide activity at Mount Meager. We used Structure from Motion photogrammetry (SfM) and Lidar to produce digital surface models and InSAR to monitor slope deformation. We applied SfM to historic photography to document glacier and landslide activity at Mount Meager. We discussed a model of growth and erosion of a volcano in glacial and interglacial periods, and the scientific and dissemination value of historic 3D topographic reconstruction. We described the 2010 Mount Meager landslide deposit to interpret emplacement dynamics and kinematics. The 2010 landslide separated in water-rich and water-poor phases that had different runout and distinct deposits. We analyzed historic airphotos to constrain the slope deformation prior to the 2010 collapse. The glacier near the toe of the slope retreated in the failure lead up, the collapse evolved in four subfailures involving the whole volcanic sequence and some basement rocks. We estimated 6 × 106 m3 of water in the slope, that allowed the separation of the frontal water-rich phase. The total failure volume was 53 ± 3.8 × 106 m3. We identified 27 large (>5×105 m2) unstable slopes at Mount Meager and calculated ~1.3 km3 of ice loss since 1987. The west flank of Plinth peak and Devastation Creek valley moved up to -34±10 mm and -36±10 mm, respectively, over a 24-day period during the summer of 2016. The failure of these slopes could impact infrastructures and communities downstream of the volcano. The resulting decompression on the volcanic edifice after the failure of Plinth peak would affect the stress field to a depth of 6 km and up to 4 MPa. This sudden decompression could lead to hydrothermal or magmatic eruptions.
23

Structure from Motion, a Cheaper Alternative for Three-Dimensional Modeling in Earth Science / Structure from Motion, ett billigare alternativ för tredimensionell modellering inom geovetenskap

Fagerström, Viktor January 2018 (has links)
In this report, two methods for three-dimensional modeling are evaluated against each other. The first method is terrestrial laser scanning (LiDAR) that uses a laser beam to record the surrounding environment, and the second one is called Structure from Motion (SfM). The SfM technique works on the same bases as photogrammetry, which is that an object of interest is photographed from multiple angles with overlapping images and mutual points are identified and used to create a three- dimensional model. Since both the equipment and the software used to produce LiDAR models are very expensive the main thought of this project was to produce the SfM model using a cellphone camera and free open source software. The study was carried out in such a way that a “before and after” -model was generated of a small snowy mound to see how well the SfM method performed compared to the LiDAR method. The final result revealed that SfM method deviated with approximately 8mm from the LiDAR method. One of the main difficulties during this project was to correctly reference the models against exact coordinate, which also could have been one reason to why the two models differed the way they did. Taking into consideration the user-friendliness and the low cost of the SfM method, it is a very promising tool for earth science related field research. / I denna rapport så kommer två metoder för att framställa tredimensionella modeller att jämföras mot varandra. Den ena metoden är markbunden laserscanning (LiDAR), vilket använder sig av en scanner som skickar ut en laserstråle som scannar av omgivningen. Den andra metoden använder en teknik som kallas för ”Structure-from- Motion” (SfM). SfMs grunder bygger på samma teknik som används inom fotogrammetri, vilket är att objektet av intresse fotograferas, med en vanlig kamera, med ett flertal överlappande bilder och gemensamma punkter i dessa bilder används för att producera en tredimensionell modell. Då både utrustning och programvaran för att producera laserscanningar är mycket kostsamma så är grundtanken med denna undersökning att endast använda en mobiltelefonkamera och gratis öppen källkod programvara för att producera SfM modellen. Själva undersökningen gick till på så sätt att en ”före och efter” modell skapades av en snöhög med båda teknikerna för att se hur bra SfM förhöll sig mot LiDAR metoden. Resultatet visade sig att SfM metoden avvek från LiDAR-resultatet med ungefär 8mm. En av de största svårigheterna med detta projekt var att korrekt referera modellerna till exakta koordinater, vilket även kan vara en av orsakerna till att modellerna inte korrelerade med varandra helt och hållet. Med tanke på användarvänligheten och kostnaden för SfM metoden så är detta ett mycket lovande verktyg för användning inom geovetenskap.
24

Image Based Indoor Navigation

Noreikis, Marius January 2014 (has links)
Over the last years researchers proposed numerous indoor localisation and navigation systems. However, solutions that use WiFi or Radio Frequency Identification require infrastructure to be deployed in the navigation area and infrastructureless techniques, e.g. the ones based on mobile cell ID or dead reckoning suffer from large accuracy errors. In this Thesis, we present a novel approach of infrastructure-less indoor navigation system based on computer vision Structure from Motion techniques. We implemented a prototype localisation and navigation system which can build a navigation map using area photos as input and accurately locate a user in the map. In our client-server architecture based system, a client is a mobile application, which allows a user to locate her or his position by simply taking a photo. The server handles map creation, localisation queries and pathnding. After the implementation, we evaluated the localisation accuracy and latency of the system by benchmarking navigation queries and the model creation algorithm. The system is capable of successfully navigating in Aalto University computer science department library. We were able to achieve an average error of 0.26 metres for successfully localised photos. In the Thesis, we also present challenges that we solved to adapt computer vision techniques for localisation purposes. Finally we observe the possible future work topics to adapt the system to a wide use. / Forskare har de senaste åren framfört olika inomhusnavigations- och lokaliseringssystem. Dock kräver lösningar som använder WiFi eller radiofrekvens identifikation en utbyggdnad av stödjande infrastruktur i navigationsområdena. Även teknikerna som används lider av precisionsfel. I det här examensarbetet redovisar vi en ny taktik för inomhusnavigation som använder sig av datorvisualiserings Structure from Motion-tekniker. Vi implementerade en navigationssystemsprototyp som använder bilder för att bygga en navigationskarta och kartlägga användarens position. I vårt klient-server baserat system är en klient en mobilapplikation som tillåter användaren att hitta sin position genom att ta en bild. På server-sidan hanteras kartor, lokaliseringsförfrågor och mättningar av förfrågorna och algoritmerna som används. Systemet har lyckats navigera genom Aalto Universitets datorvetenskapsbiblioteket. Vi lyckades uppnå en felmarginal pa 0.26 meter för lyckade lokaliseringsbilder. I arbetet redovisar vi utmaningar som vi har löst för att anpassa datorvisualiseringstekniker for lokalisering. Vi har även diskuterat potentialla framtida implementationer for att utvidga systemet.
25

Volymberäkning från punktmoln skapatgenom Structure from Motion medbildunderlag från mobilkamera

Sigurdsson, Andreas, Lehr, Amadeus January 2021 (has links)
Tekniken hos mobiler och utvecklingen av programvaror för digitalafotogrammetriska tjänster har haft en snabb utveckling, vilket har gjort detmöjligt att enkelt kunna skapa 3D-modeller.Syftet med denna studie är att undersöka om det är möjligt att med hjälp avbildunderlag från en mobiltelefon kunna volymberäkna objekt så som t.ex.grushögar och diken. Den teknik som används är en automatiskbildjusteringsalgoritm som heter Structure from Motion (SfM). Från en seriedigitalafoton, som täcker objektet från olika vinklar och djup kan SfMidentifiera gemensamma punkter i fotona och sammanfläta dessa till ettpunkmoln som kan användas för att skapa en 3D-modell. Utifrån 3Dmodellen kan sedan en volymbestämning ske från mjukvaran AgisoftMetashape.Denna studie utför ett flertal olika tester för att utvärdera Structure fromMotion med bildunderlag från mobiltelefon för volymberäkning. Vissa objekthar att filmats med olika typer av telefoner och sedan jämförts mot terresterlaserskanning (TLS) som är en vanlig metod vid insamling av data förvolymberäkning. Volymberäkningarna har gjorts för både positiva ochnegativa volymer. Metoden har enbart använt sig av referensmått frånmåttband ute i fält. Detta gör att ingen avancerad mätutrustning har använts.Ett ljustest genomfördes för att se hur olika ljusförhållanden viddatainsamlandet kan påverka databearbetningen och volymberäkningen.Genom att beräkna skillnader i volym mellan 3D-modellerna kommer ettresultat tas fram.Resultaten från de 3D-modeller som skapats med dataunderlag från SfM gervolymskillnader i jämförelsen mot terrester laserskanning mellan 2,2% och6,8%. Dessa resultat är från en mur och ett dike som användes i studien,skillnaden motsvarar 0,031 m3 och 15,086 m3. Den negativa volym somberäknades, dvs. diket, är det objekt som ger störst avvikelse i volym, delsmellan de olika mobiltelefonerna, dels jämfört med TLS. Metoden ger enindikation på att det finns en stor möjlighet att kunna effektivisera processenför volymbestämning då metoden inte kräver speciella mätverktyg ellersärskilda förkunskaper vilket kan både spara tid och pengar. / The technology of smartphones and the development of software for digitalphotogrammetric services have developed rapidly, which has made it possibleto easily create 3D models.The purpose of this study is to investigate whether it is possible with the helpof image data from a mobile phone to be able to calculate the volume ofobjects such as e.g. gravel piles and ditches. The technology used is anautomatic image adjustment algorithm called Structure from Motion (SfM).From a series of digital photos, which cover the object from different anglesand depths, SfM can identify common points in the photos and intertwinethese into a point cloud that can be used to create a 3D model. Based on the3D model, a volume determination can then be made from the AgisoftMetashape software.This study performed a number of different tests to evaluate Structure fromMotion with image data from a smartphone for volume calculation. Someobjects have been filmed with different types of phones and then compared toterrestrial laser scanning (TLS) which is a common method of collecting datafor volume calculation. The volume calculations have been made for bothpositive and negative volumes. The method has only used referencemeasurements from measuring tapes in the field. This means that no advancedmeasuring equipment has been used. A light test was performed to see howdifferent light conditions during the data collection can affect the dataprocessing and volume calculation. By calculating differences in volumebetween the 3D models, a result will be produced.The results from 3D modeling created with data from SfM give a volumedifferences in the comparison with terrestrial laser scanning between 2.2%and 6.8%. These results are from a small stone wall and a ditch used in thestudy, the difference corresponds to 0.031 m3and 15.086 m3. The negativevolume that was calculated, ie. the ditch, is the object that gives the largestdeviation in volume, partly between the different mobile phones, partlycompared to TLS. The method gives an indication that there is a greatopportunity to be able to streamline the work process for volume calculationas the method does not require special measurement tools or special priorknowledge which can save both time and money.
26

THE EVALUATION OF MEASURING STREAM CHANNEL MORPHOLOGY USING UNMANNED AERIAL SYSTEM-BASED STRUCTURE-FROM-MOTION PHOTOGRAMMETRY

Ballow, William 12 August 2016 (has links)
As part of a collaborative project at a stream segment reach on Proctor Creek in Atlanta, GA, UAV-based SfM photogrammetry was tested as a method for collecting fluvial topographic data relative to traditional USGS total station surveying methods. According to the USGS method, 11 transects were surveyed, and imagery was collected via a UAV to create a SfM DEM. The resulting DEM was incomplete but showed promise for the SfM method. Two additional stream segments were chosen in the Atlanta area, the first along SFPC in DHCL and the second along NFPC near Buford Hwy. For each site 11 transects were surveyed along with submerged GCPs so that the SfM DEMs could be compared to the surveyed data. The BW and BD values were collected from the TS transects and the DEM transects and compared according to the percent difference between the two. For SFPC, the average percent difference values for BW and BD were, respectively, 15.9 and 26.0 with standard deviations of 15.7 and 18.0. For NFPC, the BW and BD average percent difference values were 6.8 and 7.5 with standard deviations of 3.9 and 5.9. The GCPs were also compared for each site using linear regressions. There was no strong correlation for SFPC (R2 = 0.31 and p-value > 0.05), but there was a strong relationship indicated for NFPC (R2 = 0.78 and p-value < 0.05). While the results of this study are variable, the results do indicate promise for future work on this emerging method.
27

SAR remote sensing of soil moisture

Snapir, Boris January 2014 (has links)
Synthetic Aperture Radar (SAR) has been identified as a good candidate to provide high-resolution soil moisture information over extended areas. SAR data could be used as observations within a global Data Assimilation (DA) approach to benefit applications such as hydrology and agriculture. Prior to developing an operational DA system, one must tackle the following challenges of soil moisture estimation with SAR: (1) the dependency of the measured radar signal on both soil moisture and soil surface roughness which leads to an ill-conditioned inverse problem, and (2) the difficulty in characterizing spatially/temporally surface roughness of natural soils and its scattering contribution. The objectives of this project are (1) to develop a roughness measurement method to improve the spatial/temporal characterization of soil surface roughness, and (2) to investigate to what extent the inverse problem can be solved by combining multipolarization, multi-incidence, and/or multi-frequency radar measurements. The first objective is achieved with a measurement method based on Structure from Motion (SfM). It is tailored to monitor natural surface roughness changes which have often been assumed negligible although without evidence. The measurement method is flexible, a.ordable, straightforward and generates Digital Elevation Models (DEMs) for a SAR-pixel-size plot with mm accuracy. A new processing method based on band-filtering of the DEM and its 2D Power Spectral Density (PSD) is proposed to compute the classical roughness parameters. Time series of DEMs show that non-negligible changes in surface roughness can happen within two months at scales relevant for microwave scattering. The second objective is achieved using maximum likelihood fitting of the Oh backscattering model to (1) full-polarimetric Radarsat-2 data and (2) simulated multi-polarization / multi-incidence / multi-frequency radar data. Model fitting with the Radarsat-2 images leads to poor soil moisture retrieval which is related to inaccuracy of the Oh model. Model fitting with the simulated data quantifies the amount of multilooking for di.erent combinations of measurements needed to mitigate the critical e.ect of speckle on soil moisture uncertainty. Results also suggest that dual-polarization measurements at L- and C-bands are a promising combination to achieve the observation requirements of soil moisture. In conclusion, the SfM method along with the recommended processing techniques are good candidates to improve the characterization of surface roughness. A combination of multi-polarization and multi-frequency radar measurements appears to be a robust basis for a future Data Assimilation system for global soil moisture monitoring.
28

Applications of Structure-from-Motion Photogrammetry to Fluvial Geomorphology

Dietrich, James 14 January 2015 (has links)
Since 2011, Structure-from-Motion Multi-View Stereo Photogrammetry (SfM or SfM-MVS) has gone from an overlooked computer vision technique to an emerging methodology for collecting low-cost, high spatial resolution three-dimensional data for topographic or surface modeling in many academic fields. This dissertation examines the applications of SfM to the field of fluvial geomorphology. My research objectives for this dissertation were to determine the error and uncertainty that are inherent in SfM datasets, the use of SfM to map and monitor geomorphic change in a small river restoration project, and the use of SfM to map and extract data to examine multi-scale geomorphic patterns for 32 kilometers of the Middle Fork John Day River. SfM provides extremely consistent results, although there are systematic errors that result from certain survey patterns that need to be accounted for in future applications. Monitoring change on small restoration stream channels with SfM gave a more complete spatial perspective than traditional cross sections on small-scale geomorphic change. Helicopter-based SfM was an excellent platform for low-cost, large scale fluvial remote sensing, and the data extracted from the imagery provided multi-scalar perspectives of downstream patterns of channel morphology. This dissertation makes many recommendations for better and more efficient SfM surveys at all of the spatial scales surveyed. By implementing the improvements laid out here and by other authors, SfM will be a powerful tool that will make 3D data collection more accessible to the wider geomorphic community.
29

Estudo sobre a fisiologia da paisagem do areal do Cerro da Esquina no município de São Francisco de Assis - RS

Rodrigues, Éder Luis da Silva January 2018 (has links)
A presente pesquisa estudou a dinâmica dos processos de arenização atuantes no areal do Cerro da Esquina, no município de São Francisco de Assis - RS pela perspectiva da fisiologia da paisagem proposta por Ab’Saber em 1969. O recorte temporal do estudo foi de um ano, de junho de 2016 a março de 2017. Nesse período foram realizados quatro trabalhos de campo, no final de cada estação do ano, nos quais foram efetuados levantamentos aerofotogramétricos com um veículo aéreo não tripulado. A partir dos produtos cartográficos obtidos, foram identificadas as principais micro-feições de relevo e realizada a compartimentação do areal em cinco setores de acordo com a sua drenagem. Tais compartimentos foram analisados e caracterizados de acordo com os processos atuantes. A partir da análise minuciosa de cada setor, foi elaborado um mapa síntese da fisiologia da paisagem do areal. Durante o período estudado, observou-se que os processos de erosão, transporte e deposição de origem hídrica foram os predominantes na maior parte do areal. Em relação à área ocupada pelo areal, observou-se que esta não sofreu alteração significativa, ou seja, areal manteve-se estável. Não foram observados avanços significativos da mancha de areia em direção ao campo, nem o contrário – avanço do campo sobre o areal. Considera-se, por fim, que o monitoramento com a utilização de VANT apoiado por outras técnicas de levantamento topográfico é muito eficiente em pesquisas como a que foi realizada, pois permite o levantamento de um grande volume de informações com qualidade cartográfica, com menores custos e com resolução temporal variável de acordo com os objetivos da pesquisa. / The present research has studied the dynamics of sand forming process in sandspot of Cerro da Esquina, in São Francisco de Assis – RS under the perspective of the physiology studies of landscapes proposed by Ab’Saber in 1969. The time frame for the study was one year – from June, 2016 to March, 2017 –, in which were performed four aerophotogrammetric surveys through unmanned aerial vehicle, one survey at the end of each season of the year. Based on the cartographic data obtained, it was possible to identify the main micro features of relief and the area was compartmentalized in five sections, according to its drainage process. The compartments were analyzed and described according to the processes active in them. A sintesys map of the physiology of the areal landscape was created based on a detailed analysis of each section. During the time frame of the study, the data showed that the processes prevailing in the major part of the area were erosion, transportation and deposition with hydric origins. In what regards the total area occupied by the areal, it didn’t suffer any significant changes, what means it kept stable. There were not found significative advances in sandspots towards the surrounding meadow, nor the opposite – from the meadow towards the areal. Lastly, there are strong indications that monitoring an area with unmanned aerial vehicle and the support of other techniques of topographic survey is highly efficient in researches like the present study, once it enables a large data collection with cartographic quality, with lesser costs and the adequate variable temporal resolution according to the objectives of the research.
30

Exploring the multiple techniques available for developing an understanding of soil erosion in the UK

Benaud, Pia Emma January 2017 (has links)
Accelerated soil erosion and the subsequent decline in soil depth has negative environmental, and consequently financial, impacts that have implications across all land cover classifications and scales of land management. Ironically, although attempts to quantify soil erosion nationally have illustrated that soil erosion can occur in the UK, understanding whether or not the UK has a soil erosion problem still remains a question to be answered. Accurately quantifying rates of soil erosion requires capturing both the volumetric nature of the visible, fluvial pathways and the subtle nature of the less-visible, diffuse pathways, across varying spatial and temporal scales. Accordingly, as we move towards a national-scale understanding of soil erosion in the UK, this thesis aims to explore some of the multiple techniques available for developing an understanding of soil erosion in the UK. The thesis first explored the information content of existing UK-based soil erosion studies, ascertaining the extent to which these existing data and methodological approaches can be used to develop an empirically derived understanding of soil erosion in the UK. The second research chapter then assessed which of two proximal sensing technologies, Terrestrial Laser Scanning and Structure-from-Motion Multi-view Stereo (SfM-MVS), is best suited to a cost-effective, replicable and robust assessment of soil erosion within a laboratory environment. The final research chapter built on these findings, using both Rare Earth Oxide tracers and SfM-MVS to elucidate retrospective information about sediment sources under changing soil erosion conditions, also within a laboratory environment Given the biased nature of the soil erosion story presented within the existing soil erosion research in the UK, it is impossible to ascertain if the frequency and magnitude of soil erosion events in the UK are problematic. However, this study has also identified that without ‘true’ observations of soil loss i.e. collection of sediment leaving known plot areas, proxies, such as the novel techniques presented in the experimental work herein and the methods used in the existing landscape scale assessments of soil erosion as included in the database chapter, are not capable of providing a complete assessment of soil erosion rates. However, this work has indicated that despite this limitation, each technique can present valuable information on the complex and spatially variable nature of soil erosion and associated processes, across different observational environments and scales.

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