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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.
71

Detektering av sättningar med hjälp av UAV fotogrammetri : En jämförelsestudie mellan direkt och indirekt georeferering

Nilsson, Olof, Olsson, Linda January 2022 (has links)
Att tidigt kunna detektera samt åtgärda sättningar och deformationer är viktigt inom exempelvis bygg-, anläggnings- och gruvindustrin för att kontrollera att verksamheten inte påverkar närliggande områden och strukturer. UAV (Unmanned Aerial Vehicle) fotogrammetri är en lämplig metod för att utföra upprepade mätningar i svårtillgänglig miljö där sättningar kan uppkomma. Syftet med denna studie har varit att undersöka möjligheten till att detektera sättningar med UAV fotogrammetri samt att jämföra direkt och indirekt georeferering. Detta har undersökts genom att ett antal objekt har använts till att simulera sättningar med förändringar på centimeternivå. Området som studien utfördes på flögs över med en fotogrammetrisk UAV i två epoker varav den första epoken var innan sättning och den andra epoken var efter en simulerad sättning av objekten. Punkter markerades på objekten vilka mättes in med totalstation för båda epokerna och dessa mätningar användes som referensvärden (hädanefter kallat True Value). Bearbetning skedde därefter i två programvaror: Agisoft Metashape och Leica Infinity. I Metashape skapades punktmoln för båda epokerna indirekt georefererade med markstödpunkter. I Infinity skapades punktmoln för båda epokerna direkt georefererade med Nätverks-RTK (N-RTK). Punktmolnens avvikelser mot kontrollpunkter kontrollerades. Koordinater för markeringarna på objekten extraherades och jämfördes med koordinater inmätta med totalstation. Resultatet av bearbetningen blev fyra olika punktmoln. I de indirekt georefererade punktmolnen var det möjligt att detektera deformeringar på centimeternivå. Det var däremot inte möjligt i de direkt georefererade punktmolnen då de var påverkade av ett systematiskt fel i höjd. De två programvarornas arbetsgång och resultat jämfördes även mot varandra och där kan det konstateras att om de två programvarorna båda har höga systemkrav så var Leica Infinity betydligt mer krävande både vad gäller hårdvara och tidsåtgång än Agisoft Metashape. De slutsatser vi kan dra utifrån denna studie är att N-RTK ännu inte är en tillräckligt bra georefereringsmetod när låga osäkerheter efterfrågas. I detta fall är indirekt georeferering eller registrering av punktmolnen med hjälp av ICP (Iterative Closest Point) algoritmer att föredra. Det är också viktigt att generera punktmoln med en så hög punkttäthet som möjligt för att kunna göra noggranna mätningar i molnen. / The early detection and measure of subsidence and deformations is important within construction-, civil engineering and the mining industry to control whether the operations affect nearby areas and structures. UAV (Unmanned Aerial Vehicle) photogrammetry is a suitable method to conduct repeated measurements in environments which is hard to access where subsidence can occur. The purpose of this study has been to investigate the possibility of detecting subsidence with UAV photogrammetry and compare direct and indirect georeferencing. This has been investigated by using several objects to simulate subsidence at centimeter level. The area where the study was conducted was flown over with a photogrammetric UAV in two epochs of which the first epoch was before subsidence and the second epoch was after a simulated subsidence of the objects. Points was marked on the objects who were measured with a total station for both epochs and these measurements was used as reference values (hereafter called True Value). Processing was thereafter done in two different software: Agisoft Metashape and Leica Infinity. In Metashape point clouds was created for both epochs indirectly georeferenced with ground control points. In Infinity point clouds was created for both epochs directly georeferenced with Network-RTK (N-RTK). The deviations of the point clouds towards checkpoints were verified. Coordinates of the markings on the objects was extracted and compared against coordinates measured with total station. The photogrammetric processing resulted in four different point clouds. In the indirectly georeferenced pointclouds it was possible to detect deformations at centimeterlevel. This was however not possible using the directly georeferenced pointclouds as they were affected by a systematic error in heigth. The workflow and the resulting point clouds from the two different software was also compared to each other and by that it was established that even though they both have high system requirements the Leica Infinity software was much more demanding and additionally time consuming. The conclusion from this study is that N-RTK is not yet a satisfactory method for georeferencing when low uncertainties are required. In this case, indirect georeferencing or registration of the point clouds with ICP (Iterative Closest Point) algorithms is to be preferred. It is also important to create point clouds with the highest density possible to be able to make exact measurements.
72

Spatial distribution of the rodent population at Boundary Stream Mainland Island and determination of the efficacy of different baits used for rodent control

Wissel, Silke January 2008 (has links)
Poison operations are a widely used technique for rodent control in the indigenous forests of New Zealand. This study examined the bait-take and rat monitoring data obtained for continuous poison operations at Boundary Stream Mainland Island (BSMI), Hawke’s Bay, between 1996 and 2007. Since the beginning of the Mainland Island project at BSMI in 1996, 800 ha of indigenous forest have been treated with an ‘Integrated Pest Management’ approach, in which rodents (primarily ship rats) have been targeted by consecutive ground poison operations. The aim of the intensive pest control was to allow the ecosystem to recover and provide a safe environment for threatened native bird species to recover or be re-introduced. Another important aim of this pest control is to provide experience and expert knowledge in management techniques especially applicable to the protection of indigenous habitat on the New Zealand mainland. This research study had two main aims: to identify spatial patterns of the rodent population at BSMI and to determine the efficacy of the different rodenticides applied for their control. The distribution of the rodent population was investigated by spatial analysis of bait-take across the reserve and through time. Visualisation of high and low bait-take areas revealed that there was a noticeable reinvasion from adjacent unmanaged native forests, but not markedly from exotic forest or pasture. Reinvasion from small and isolated adjacent forests ceased to be noticeable consistently after approximately four years of the poison operation, while a large scenic native reserve, as well as a narrow part of the treatment area surrounded by many native bush patches, were continuously affected by reinvasion through the entire project time. Bait-take was visibly higher after the bait had either been removed, or left in the field unserviced, over winter. No consistent areas of no bait-take were identified. Further statistical analysis of bait-take data revealed that bait-take was higher in bait stations within 150 m of the treatment edge than interior bait stations. Bait-take in broadleaf/tawa/podocarp forest was significantly higher than in kamahi/kanuka/rewarewa, beech and cloud-cap forest. The second aim of the study was to determine the efficacy of the various bait types with different active ingredients used during the operation. Rat monitoring data, namely rat tracking indices (RTI) obtained from tracking tunnels, were statistically modelled using Generalised Linear Models. Diphacinone cereal pellets (Pestoff® 50D, 0.05g/kg diphacinone) obtained the lowest RTI, followed by pindone cereal pellets (Pindone Pellets®, 0.5g/kg pindone), brodifacoum cereal pellets (Pestoff® 20p and Talon®, 0.02 g/kg brodifacoum), coumatetralyl paste (Racumin®, 0.375 g/kg) and diphacinone bait blocks (Ditrac®, 0.05 g/kg). Cereal pellet baits worked better than any other bait type used at this location. Season had no statistically significant effect on either RTI or bait-take estimates. The overall goal of the poison operation to decrease rat numbers, and to maintain low levels, has been met. However, the results of this study suggest that baiting needs to be done continuously and over the entire treatment area. Edge bait stations – particularly next to adjacent native forests – should be prioritised to target reinvading rodents. Poisons presented in cereal pellet baits should be preferred to other bait types. Both pindone and brodifacoum showed very good results, as well as diphacinone in cereal pellet baits.
73

Vyhodnocení snímků pořízených pomocí UAV / Evaluation of data captured by UAV

Martináková, Veronika January 2018 (has links)
The master´s thesis deals with the application of unmanned aerial vehicle (UAV) in photogrammetry and mapping. The first part describes the UAV that was used for imaging, legislative restrictions resulting from its operations, planning and realization of the flight. The second part of this thesis is focused on processing results, especially on evaluation the accuracy of the results gained by UAV with and without a GNSS module. The data are evaluated in the 3rd accuracy rating class (ČSN 01 3410). The theoretical principles are explained as well. The main aim of the thesis is to demonstrate the effective use of the GNSS module Emlid Reach and the unmanned aerial vehicle in geodesy.

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