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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.
1

Mätosäkerhet vid indirekt längdmätning med laserskanner Leica BLK360

Stawe, Daniel January 2018 (has links)
The need for 3D-data has increased in the modern society. The data is used in many applications such as terrain models, documentation of buildings and infrastructure and can also be used for restauration or when monitoring deformations. Laser ranging is an important source to collect this type of information. Technical development has contributed with smaller and cheaper units and increased performance. Leica BLK360 was released in 2016 and is an example of this technological upraise. Since the model is new, it is interesting to investigate its performance. The goal of the study was to evaluate the performance of the length measurements by performing indirect measurements, as well as to investigate the range noise. These tests were performed at targets at different range indoors. The study took place at the lab facility at Heimdall at the University of Gävle. The method that was used, was to perform indirect measurements with targets on a line. The targets were placed with approximately 10 m in between. The results of scanned parallel targets were measured, it shows uncertainty that is smallest at 30 m (just over 2 mm) and highest at 40 m (over 5 mm). No statistical differences could be confirmed in this data. When non parallel targets was measured, the calculated uncertainty differences were 2–3 mm at 20–40 m (0° scanning angle). Low uncertainty was measured at 0° scanning angle, at higher angles uncertainties are increased. Differences could only be statistically confirmed on 40 m 45° and 10 m 0°. A conclusion from the investigation is that the measured uncertainties would be larger than if direct measurements was made. The results in this study based off indirect measurements, could not be compared to results made by direct measurements. The uncertainties would however be smaller in this type of study. When investigated the range noise it showed close to a linear curve in different scanning angles, when studying distance at 0–30 m except the target at 10 m. Statistically significant differences could be found for most measurements of range noise. The range noise is not specified in the user manual. The scanner works well at scanning indoor spaces, the low density point cloud at far range could be a limiting factor in some situations. / Behovet av 3-D data är stort i dagens samhälle. Det kan användas till att göra terrängmodeller, vid dokumentation av byggnader och anläggningar för renovering eller mätning av deformation etc. Laserskanning är ett viktigt sätt att samla in den typen av information. Teknisk utveckling har bidragit starkt till att förbättra prestanda, bidra till lägre vikt för enheterna och sänka kostnaderna för denna typ av utrustning. Leica BLK360 är en skanner som lanserades 2016 och är en tydlig representant för denna utveckling. Då skannern är ny finns intresse att undersöka dess prestanda, vilket görs i detta arbete. Målet med studien var att bedöma mätosäkerhet mot signaltavlor bestående av svagt gråtonade skivor på vissa givna avstånd, vilket kom att ske i inomhusmiljö. Dessa mätningar gjordes med indirekt längdmätning och slutsatser kring resultatens giltighet vid direkt längdmätning drogs. En bedömning gjordes också av avståndsbrusets storlek vid olika infallsvinklar. Arbetet syftade till att uppnå målen genom tester som utfördes i laborationshallen Heimdall på Högskolan i Gävle (HIG). Längdmätningsosäkerheter beräknades genom RMS-värden och resultatet för mätningar vid parallella plan visar att skillnader mot referensavstånd är lägst vid 30 m (drygt 2 mm) och det högsta värdet på signalen vid 40 m (drygt 5 mm). Generellt var det statistiska underlaget inte tillräckligt stort för att dra slutsatser kring skillnaderna i dessa längdmätningar. För motsvarande bedömning vid icke-parallella plan visade resultaten 2–3 mm vid 0° för längder på 20–40 m. Vid större infallsvinklar ökade sedan mätosäkerheten. Från de flesta av mätningarna kunde inte statistisk skillnad säkerställas på grund av liten mätserie, det kunde främst konstateras skillnad mellan värdet på 40 m 45° samt 10 m 0°. En slutsats som drogs är att de osäkerheter som uppmättes kunde anses större än om direkt längdmätning hade använts. Vid undersökning av avståndsbrusets storlek upptäcktes en förhållandevis linjär utveckling vid de olika infallsvinklarna, om bedömning enbart görs vid 0–30 m. Vid dessa mätningar kunde statistiska säkerställda skillnader konstateras i mycket hög omfattning. Skannern fungerar bra vid skanning inomhus, något som kan upplevas som en begränsning är ett förhållandevist glest punktmoln på längre avstånd, särskilt vid större infallsvinklar
2

A game theoretic analysis of adaptive radar jamming

Bachmann, Darren John Unknown Date (has links) (PDF)
Advances in digital signal processing (DSP) and computing technology have resulted in the emergence of increasingly adaptive radar systems. It is clear that the Electronic Attack (EA), or jamming, of such radar systems is expected to become a more difficult task. The reason for this research was to address the issue of jamming adaptive radar systems. This required consideration of adaptive jamming systems and the development of a methodology for outlining the features of such a system is proposed as the key contribution of this thesis. For the first time, game-based optimization methods have been applied to a maritime counter-surveillance/counter-targeting scenario involving conventional, as well as so-called ‘smart’ noise jamming.Conventional noise jamming methods feature prominently in the origins of radar electronic warfare, and are still widely implemented. They have been well studied, and are important for comparisons with coherent jamming techniques.Moreover, noise jamming is more readily applied with limited information support and is therefore germane to the problem of jamming adaptive radars; during theearly stages when the jammer tries to learn about the radar’s parameters and its own optimal actions.A radar and a jammer were considered as informed opponents ‘playing’ in a non-cooperative two-player, zero-sum game. The effects of jamming on the target detection performance of a radar using Constant False Alarm Rate (CFAR)processing were analyzed using a game theoretic approach for three cases: (1) Ungated Range Noise (URN), (2) Range-Gated Noise (RGN) and (3) False-Target (FT) jamming.Assuming a Swerling type II target in the presence of Rayleigh-distributed clutter, utility functions were described for Cell-Averaging (CA) and Order Statistic (OS) CFAR processors and the three cases of jamming. The analyses included optimizations of these utility functions, subject to certain constraints, with respectto control variables (strategies) in the jammer, such as jammer power and spatial extent of jamming, and control variables in the radar, such as threshold parameter and reference window size. The utility functions were evaluated over the players’ strategy sets and the resulting matrix-form games were solved for the optimal or ‘best response’ strategies of both the jammer and the radar.
3

A game theoretic analysis of adaptive radar jamming

Bachmann, Darren John Unknown Date (has links) (PDF)
Advances in digital signal processing (DSP) and computing technology have resulted in the emergence of increasingly adaptive radar systems. It is clear that the Electronic Attack (EA), or jamming, of such radar systems is expected to become a more difficult task. The reason for this research was to address the issue of jamming adaptive radar systems. This required consideration of adaptive jamming systems and the development of a methodology for outlining the features of such a system is proposed as the key contribution of this thesis. For the first time, game-based optimization methods have been applied to a maritime counter-surveillance/counter-targeting scenario involving conventional, as well as so-called ‘smart’ noise jamming.Conventional noise jamming methods feature prominently in the origins of radar electronic warfare, and are still widely implemented. They have been well studied, and are important for comparisons with coherent jamming techniques.Moreover, noise jamming is more readily applied with limited information support and is therefore germane to the problem of jamming adaptive radars; during theearly stages when the jammer tries to learn about the radar’s parameters and its own optimal actions.A radar and a jammer were considered as informed opponents ‘playing’ in a non-cooperative two-player, zero-sum game. The effects of jamming on the target detection performance of a radar using Constant False Alarm Rate (CFAR)processing were analyzed using a game theoretic approach for three cases: (1) Ungated Range Noise (URN), (2) Range-Gated Noise (RGN) and (3) False-Target (FT) jamming.Assuming a Swerling type II target in the presence of Rayleigh-distributed clutter, utility functions were described for Cell-Averaging (CA) and Order Statistic (OS) CFAR processors and the three cases of jamming. The analyses included optimizations of these utility functions, subject to certain constraints, with respectto control variables (strategies) in the jammer, such as jammer power and spatial extent of jamming, and control variables in the radar, such as threshold parameter and reference window size. The utility functions were evaluated over the players’ strategy sets and the resulting matrix-form games were solved for the optimal or ‘best response’ strategies of both the jammer and the radar.

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