L’infrarouge proche (1.5-2μm) ou SWIR (Short Wavelength Infrared) est une région particulièrement adaptée à la mesure de gaz à effet de serre par lidar à absorption différen- tielle (DIAL). En effet, (i) cet intervalle spectral contient des raies d’absorption intenses pour les principaux gaz à effet de serre (CO2, CH4, H2O, etc.) (ii) le taux d’extinction lors de la propagation du faisceau laser y est faible (iii) c’est une région spectrale dite en sécurité oculaire. Bien qu’abordée avec les moyens existants (détection hétérodyne), la mesure DIAL dans le SWIR a longtemps souffert de l’absence de photo-détecteurs ultra-sensibles. Les développements récents (années 2000) portant sur les photodiodes à avalanche (APD) HgCdTe ont changé la donne. En effet, ces dernières présentent de remarquables qualités d’amplification car elles allient trois propriétés fondamentales : un faible excès de bruit, un très faible courant d’obscurité et des gains importants. De telles propriétés sont essentielles pour les applications reposant sur la détection de très faibles signaux et en particulier le lidar.Dans cette thèse, nous analysons les performances d’un détecteur monopixel (200 μm) à base d’APD HgCdTe (conçu sur mesure par le CEA-LETI) dans le cadre de mesures expérimentales de la concentration de CO2 atmosphérique par lidar DIAL. L’émetteur laser est également un prototype, précédemment développé au Laboratoire de Météoro- logie Dynamique. Il produit alternativement des impulsions de 10 mJ à deux fréquences contrôlées dans la plage 2050-2054nm, le tout à une fréquence de répétition de 2kHz. Grâce à l’association de ces deux technologies de pointe nous avons pu effectuer les pre- mières mesures DIAL utilisant la technologie HgCdTe APD.Les expériences menées nous ont permis de confirmer le remarquable niveau de per- formances en sensibilité attendu (75 photons de bruit par temps caractéristique d’une bande passante de 20 MHz) et soulignent le potentiel futur d’un tel capteur pour toutes les applications faible flux dans le SWIR. Concernant les mesures DIAL, nous avons ob- tenu expérimentalement une précision relative de 10-20 % sur la concentration en CO2 pour une mesure dans la couche limite avec une résolution de 100 m - 4 s sur une portée de 1.5km. Par ailleurs, l’analyse fine de la réponse impulsionnelle de la photodiode à avalanche révèle une dégradation notable du long term settling time lorsqu’on la pola- rise. Ce phénomène contraint la plage d’utilisation du capteur, ce que nous discutons en tenant ce comportement du détecteur dans une simulation lidar. / The Short Wavelength Infrared (SWIR) region (1.5-2 μm) is well adapted for diffe- rential absorption lidar technique (DIAL) for several reasons : (i) it covers absorption bands with suitable intensity for the main greenhouse gases (CO2, CH4, H2O, etc.) (ii) the extinction due to particles is low (iii) it belongs to the eye safe domain. However, one main drawback has long been the lack of efficient photodetectors for such frequencies. A major enhancement occurred in the early 2000s when it was understood that HgCdTe avalanche photodiodes (APD) present close to unity excess noise factor on top of high gain and very low dark current. These features make this technology an almost ideal amplifier, especially useful for ultra low flux applications such as lidar.In this thesis, we analyze the performances of a custom large diameter (200μm) monopixel HgCdTe-APD based detector (designed at CEA-LETI) in the framework of atmospheric CO2 measurements with the DIAL technique. The laser emitter, a custom solid-state Ho :YLF laser developed at the Laboratoire de Météorologie Dynamique, is tunable in the 2050-2054nm range and produces 10 mJ pulses at a repetition rate of 2kHz. This emitter is associated to a detection chain adapted to the HgCdTe APD based detector to provide the first atmospheric DIAL measurements using the HgCdTe APD technology.Experiments confirmed the outstanding sensitivity of the detector (75 noise photons per characteristic time given a 20MHz bandwidth) and highlight the huge potential of this technology for any application relying on low light flux detection in SWIR. With the system previously mentioned, we reach an precision of 10-20 % on CO2 mixing ratio for a time-space resolution of 100 m and 4 s for measurements in the atmospheric boundary layer. Regarding the detector impulse response, we have shown evidence of a negative influence of reverse bias on the long term settling time of the APD. This phenomenon limits the dynamic range of useful signals and contraints the DIAL system. Thanks to numerical simulation taking into account this behaviour, we derive numerically expected biases on DIAL measurements.

Pour estimer les puits et sources des gaz à effet de serre et améliorer les prévisions d’évolution du climat, il est nécessaire de disposer de mesures précises et continues de leurs concentrations atmosphériques à l’échelle globale. Pour consolider le réseau d’observation mondial, la mise en œuvre de systèmes lidar embarqués sur satellite pour les futures missions de sondage atmosphérique depuis l’espace est considérée comme un atout à la fois innovant et complémentaire pour les méthodes de mesure actuelles. Dans ce contexte, ces travaux de thèse ont porté sur le développement d’un lidar à absorption différentielle (DIAL) à partir d’une source paramétrique émettant dans la gamme spectrale 1,9 – 2,3 µm. Il s’est agi de démontrer l’aptitude de la source à être mise en œuvre pour des mesures longue portée des principaux gaz à effet de serre (CO2, H2O, CH4). Dans ce but, la source a été intégrée dans une architecture lidar dimensionnée préalablement à l’aide une modélisation numérique. L’optimisation de l’instrument s’est faite autour de deux points : le contrôle de la pureté spectrale de la source, et la maîtrise de la réponse de la chaine de détection et d’acquisition. Des mesures des trois gaz ont ensuite été réalisées depuis le laboratoire à partir du signal provenant de la rétrodiffusion des aérosols ou des nuages. Ces mesures ont servi de support pour une étude approfondie des erreurs et biais de mesure. À partir de ces travaux et en s’appuyant sur des simulations, la possibilité d’intégration de la source dans un système aéroporté a été étudiée comme étape préliminaire à la mesure spatiale. Enfin, une projection des performances d’un système satellite mettant en œuvre la source a été établie. / Sustained and accurate greenhouse gases measurements at a global scale are required to improve the knowledge on their sources and sinks and thus increase the accuracy of climate change projections. In order to consolidate the global observation networks, spaceborne lidar systems for future earth observation missions are regarded as innovative and complementary components to the present operational measurement methods. In this context, this research work has consisted in developing a differential absorption DIAL lidar based on an optical parametric source able to emit in the 1,9–2,3 µm spectral range. The purpose was to demonstrate its ability to be implemented in long range measurements of the main greenhouse gases (CO2, H2O, CH4). Then, the laser transmitter has been integrated in a lidar architecture which was previously designed using a numerical model. Improvements and optimization of the lidar system focused on two aspects: the monitoring of the spectral purity of the emitter and the control of the detection and acquisition. Concentration measurements on the three gases have been carried out from the laboratory based on atmospheric backscattered signals from clouds and aerosol. These measurements provided a basis for the investigation of the error and bias sources. On the basis of these measurements, instrument scaling for future airborne demonstrations is discussed. Projected performances of a spaceborne instrument are also presented.

Afin de permettre une navigation autonome d'un robot dans un environnement, le robot doit être capable de percevoir son environnement. Dans la littérature, d'une manière générale, les robots perçoivent leur environnement en utilisant des capteurs de type sonars, cameras et lidar 2D. L'introduction de nouveaux capteurs, nommés lidar 3D, tels que le Velodyne HDL-64E S2, a permis aux robots d'acquérir plus rapidement des données 3D à partir de leur environnement. La première partie de cette thèse présente une technique pour la calibrage des capteurs lidar 3D. La technique est basée sur la comparaison des données lidar à un modèle de vérité de terrain afin d'estimer les valeurs optimales des paramètres de calibrage. La deuxième partie de la thèse présente une technique pour la localisation et la détection de fermeture de boucles pour les robots autonomes. La technique est basée sur l'extraction et l'indexation des signatures de petite-taille à partir de données lidar 3D. Les signatures sont basées sur les histogrammes de l'information de normales de surfaces locale extraite à partir des données lidar en exploitant la disposition des faisceaux laser dans le dispositif lidar / In order to autonomously navigate in an environment, a robot has to perceive its environment correctly. Rich perception information from the environment enables the robot to perform tasks like avoiding obstacles, building terrain maps, and localizing itself. Classically, outdoor robots have perceived their environment using vision or 2D lidar sensors. The introduction of novel 3D lidar sensors such as the Velodyne device has enabled the robots to rapidly acquire rich 3D data about their surroundings. These novel sensors call for the development of techniques that efficiently exploit their capabilities for autonomous navigation.The first part of this thesis presents a technique for the calibration of 3D lidar devices. The calibration technique is based on the comparison of acquired 3D lidar data to a ground truth model in order to estimate the optimal values of the calibration parameters. The second part of the thesis presents a technique for qualitative localization and loop closure detection for autonomous mobile robots, by extracting and indexing small-sized signatures from 3D lidar data. The signatures are based on histograms of local surface normal information that is efficiently extracted from the lidar data. Experimental results illustrate the developments throughout the manuscript

UAV/LiDAR-system har utvecklats snabbt under de senaste åren. De har blivit kompaktare och kan generera en hög punkttäthet med låg mätosäkerhet. Samtidigt har prisnivåerna sjunkit, vilket medfört att ett UAV/LiDAR-system nu kan införskaffas för några hundra tusen kronor. Det finns även mer avancerade UAV/LiDAR-system för ett par miljoner kronor.  Syftet med denna studie är att undersöka vilka skillnader som finns i kvalitet mellan två UAV/LiDAR-system i olika prisklasser. Framför allt kommer osäkerheter vid skapande av digitala terrängmodeller att studeras. De system som ingår i studien är drönaren DJI Matrice 300 RTK med LiDAR-sensorn DJI Zenmuse L1, och drönaren Microdrones md4-3000 kombinerad med LiDAR-modulen RIEGL miniVUX-1DL (mdLiDAR3000DL).  Undersökningen utfördes på en grustäkt i Rörberg utanför Gävle. En fri stationsetablering gjordes för att kunna mäta in stöd- och kontrollpunkter samt fem kontrollprofiler i terrängen. En flygning per drönare genomfördes över området. De erhållna punktmolnen bearbetades och jämfördes sedan mot kontrollpunkterna i höjdled. Även mängden brus i punktmolnen studerades. Därefter skapades digitala terrängmodeller som jämfördes mot kontrollprofilerna enligt metoden i SIS-TS 21144:2016.  Innan georeferering mot stödpunkter fanns det relativt stora skillnader mellan respektive punktmoln gällande avvikelsen i höjd. För DJI-punktmolnet blev till exempel medelavvikelsen 49 mm, medan mdLiDAR3000DL genererade en medelavvikelse på –21 mm. Efter brusreducering och inpassning av punktmolnen blev resultaten mer lika. Till exempel hade de två systemens punktmoln 13 mm i både standardavvikelse och RMS. Även de uppskattade brusmängderna var relativt lika. Den enda märkbara skillnaden var att mdLiDAR3000DL gav fler låga punkter procentuellt sett. Kontrollen av respektive DTM gav också ett jämnt resultat. DJI-systemets DTM hade en variationsvidd på 43 mm, medelavvikelsen 0 mm och standardavvikelsen 11 mm. MdLiDAR3000DL:s DTM hade 42 mm i variationsvidd, 0 mm i medelavvikelse och 8 mm i standardavvikelse.  Slutsatsen som kan dras är att det främst finns skillnader i osäkerhet innan någon databearbetning har genomförts. När punktmolnen brusreduceras och georefereras jämnas resultaten ut. Hanteringen av punktmoln har följaktligen en avgörande betydelse för osäkerheten i slutändan. Båda UAV/LiDAR- systemen kan därmed generera högkvalitativa slutprodukter. / UAV/LiDAR systems have developed rapidly in recent years. They are now more compact and can generate high point density with low uncertainty. The price level has also decreased, which entails that UAV/LiDAR systems are nowadays available for a few hundred thousand SEK. At the same time, more advanced UAV/LiDAR systems exist that cost a couple of million SEK.  The aim of this study is to investigate quality differences between two UAV/LiDAR systems in different price ranges. The focus will be on studying uncertainties when creating digital terrain models. The systems in question are the drone DJI Matrice 300 RTK with LiDAR sensor DJI Zenmuse L1, and the drone Microdrones md4-3000 combined with LiDAR sensor RIEGL miniVUX-1DL (mdLiDAR3000DL).  The study was made in a gravel pit in Rörberg outside of Gävle. A free station was set up to be able to measure ground control points (GCPs), check points, and five profiles in the terrain. One flight per drone was conducted over the area. The obtained point clouds were processed and later compared to the check points with respect to height deviations. Also, the noise level in the point clouds were studied. Digital terrain models were created and compared to the profiles according to the method in SIS-TS 21144:2016.  Before georeferencing against GCPs, there were relatively large differences between each point cloud in the height component. The DJI point cloud had for instance a mean deviation of 49 mm, while mdLiDAR3000DL generated a mean deviation of –21 mm. After noise reduction and fitting of the point clouds, the results were more even. For example, the two points clouds resulted in 13 mm in both standard deviation and RMS. Also, the estimated noise levels were rather similar. The only noticeable difference was that mdLiDAR3000DL generated a larger percentage of low points. The check of each DTM also resulted in similar results. The DTM of the DJI system reached a range of 43 mm, a mean deviation of 0 mm, and a standard deviation of 11 mm. The DTM of mdLiDAR3000DL obtained a 42 mm range, 0 mm mean deviation, and 8 mm standard deviation.  Mainly, there are differences in uncertainty before any data processing is carried out. When the point clouds are noise reduced and georeferenced, the results even out to a large extent. The handling of point clouds thus has decisive importance for the final uncertainty. Thus, both UAV/LiDAR systems can generate high-quality products.

Med hjälp av luftburen laserskanning kan stora mängder av LAS-data samlas in. Lantmäteriet, en statligmyndighet vars uppgift är att kartlägga Sverige, har gjort en rikstäckande insamling av LAS-data. Denna data ärtillgänglig för allmänheten och kan hämtas gratis från Lantmäteriet. Då insamlingen är rikstäckande ärupplösningen på LAS-datan lägre än vid en lokal insamling. Punkttätheten på LAS-datan ligger på 1–2 punkterper kvadratmeter.Detta arbete gjordes på uppdrag från Arvika kommun då de ville veta om det är möjligt att extrahera och karteraArvika tätorts urbana växlighet från Lantmäteriets gratis LAS-data. Det som efterfrågades från kommunen var ettpunktlager som visar ungefärliga positioner på träd över 3–5 meter. Punktlagret skulle ha attribut medinformation om trädens storlek. Detta hade varit användbart både för kommunens GIS-avdelning för attsimulera skuggning vid planeringar, modellera träd och framtagning av informativ växlighetsstatistik. Det skulleäven vara användbart för parkavdelningen som tidigare haft brist på data över deras urbana växlighet.Denna uppgift genomfördes genom att kombinera olika funktioner i ArcGIS Pro. Först konverterades LASdatasetet om till raster. Detta raster tas sedan multiplicerat med -1 och därmed vänds. Detta inverterade rasteranvänds i hydrologiska analysfunktioner som baserar sig på att jämföra celler med dess grannceller. På detta vistas ett punktlager fram som visar lokala höjdtoppar. Detta lager matas med höjd från raster och även ett NDVIvärde. Detta NDVI-värde tas fram från två uttagna band (band 1 och 4) från Lantmäteriets ortofoto.Ett diameter-värde beräknas genom att avgöra antalet celler som trädets krona består av. Detta värde anses bliväldigt generaliserat, men har en relativt konstant differens och bör därför kunna användas för storleksindelningav träden. De framtagna lokala höjdpunkterna filtreras även med ett par kriterier som de måste uppfylla. Dessakriterier baserar sig på några av de informativa data som framtagit s så som NDVI-värde och höjd. Detta för attfilterara bort eventuella felaktiga punkter som ej är växlighet.Arbetets resultat blev ett punktlager av drygt 21 000 punkter. Punktlagret innehaver informativa attribut i formav höjdvärde, diameter-värde, NDVI-värde, och antalet celler som kronan består av. Noggrannheten vididentifiering av träden är stark beroende av trädens form och placering. Träd med en simpel trädkronaform visarresultat med hög identifieraringsnoggrannhet. Träd med mer komplexa trädkronor (oftast stora lövträd) eller omträden är placerat så att dess trädkronor flyter samman, visar resultaten sämre identifieringsnoggrannhet.Placeringsnoggrannheten beräknades genom en jämförelse med inmätta träd från mätingenjör. Resultatet visaratt placeringen av de identifierade träden har ett medelfel på drygt 2 meter. Höjdvärde uppnår en relativ högnoggrannhet då de är direkt tagna från höjdrastret vars höjdvärde är tagna från lantmäteriets LAS-data med enviss generalisering. Diametervärdena visar låg noggrannhet men med en konstant avvikelse som skulle göravärdena möjliga att använda vid en storleksklassning av trädena. / With help of airborne laser scanning can large amount of LAS-data be collected. Lantmäteriet, a state agencywhose mission is to map Sweden, have done a nationwide collection of LAS-data. This data is available to thepublic and can be downloaded for free from Lantmäteriet. As the collection is nationwide the resolution of theLAS-data is lower than a local collection of LAS-data. The point density of the LAS-data is 1-2 points per squaremeter.This study was done on behalf of Arvika municipality as they wanted to know if it is possible to extract and mapthe urban vegetation in Arvika city from Lantmäteriets LAS-data. What was wanted from Arvika municipality wasa point layer that shows approximately positions of trees over 3-5 meters. The point layer would have attributeswith information about the size of the tree. This would be useful for the municipality’s GIS apartment tosimulate shading when planning projects, modelling trees and producing informative vegetation statistics. Itwould also be useful for the park department which previously lacked data on their urban vegetation.This project was implemented using and combining different functions in ArcGIS Pro. Firstly the LAS-dataset wasconverted to raster format. This raster is then multiplied by -1 which then is inverted. This inverted raster isbeing used in hydrological analysis functions that compares cells with their neighbours. By doing this, a pointlayer showing local height peaks is produced. This point layer is later fed with a height value from the raster anda NDVI-value. This NDVI-value is obtained by using two bands (band 1 and 4) obtained from Lantmäteriet’sorthophoto.A diameter value is calculated by determining the number of cells that make up the crown for the tree. Thisvalue is very generalized but has a relatively constant difference and could therefore be used for sizeclassification of trees. The local height points are also filtered with a couple of criteria that they must meet. Thecriteria are based on some of the informative data that has been produced like NDVI and height value. This is tofilter out any potential incorrect points that are not any form of vegetation.The result of this study consists of just over 21 000 tree points. The point layer has informative attribute whichshows height, diameter, NDVI and the amounts of cells the crown of the tree consists of. The accuracy inidentifying the trees is strongly dependent on the shape and location of the trees. Trees with a simple crownshows results with high identification accuracy. Trees with more complex (most often big deciduous trees) orwhen the trees are located close to each other so that their crowns flow together, it shows results with loweridentification accuracy. The positional accuracy was calculated by a comparison with trees measured by a surveyengineer. The results shows that the positional accuracy of identified trees have a mean deviation of just over 2meters. The height value attains a relatively high accuracy as it is directly taken from the height value inLantmäteriets LAS-dataset, with a certain generalization. The diameter value shows low accuracy but with aconstant difference which could be possible to use for tree size classification of the trees.

No description available.

Digital twins in manufacturing, logistics, retail, and healthcare can help companies makebusiness decisions by simulating changes prior to implementing such changes in real life.In robotic teleoperation, virtual reality technology such as head mounted displays canincrease operator performance. In the mining equipment industry, teleoperation is quitean established concept, using a video feed for visualization, and often similiar or the samecontrol panels as on the real machine. However, cameras don’t provide depth perceptionfor the operator, and the lighting conditions in a mine may make photogrammetry a lessthan ideal solution. Epiroc is currently working on a digital twin simulation softwarein Unity, which could be extended for teleoperation purposes. As a complement to thissoftware, a fast, high-definition Ouster OS0-128 LiDAR was used to render a point cloudof a physical environment. A Unity GameObject script was written in C# that receivesand renders coordinates as a point cloud. Two Python scripts were written to convert theLiDAR data using the Ouster SDK to coordinates, and then sending these coordinates overa TCP connection, either on the same machine, or over Wi-Fi. The Python scripts used twodifferent data formats, and the performance difference between these two data formatswas compared. The results indicated that Wi-Fi transfer of LiDAR data could be a viablesolution to continously scanning the surrounding area of equipment being teleoperatedwith quite a low delay and latency

LiDAR is a remote sensing technology that uses a laser to map the surrounding environment. With its many applications, for example in autonomous vehicles, LiDAR is a growing field within technology and research. The silicon photomultiplier (SiPM) is a solid state device commonly used in the receiving system of a LiDAR. However, ambient light from sun or other light sources is also seen by the photodetector which creates noise in the receiving system. The purpose of this work is to examine how the performance of a 1D LiDAR with a SiPM receiver can be predicted, given a certain level of ambient light, target reflectance and measuring distance. This was carried through by working with mathematical models and comparing the outcomes to lab measurements of a certain LiDAR model. The outcome showed that describing the performance of the particular LiDAR by a model based on incident photon rate was difficult mainly due to the unknown relation between how the voltage signal threshold in the receiving electric circuit for when the LiDAR stops the time measurement relates to the number of microcells activated in the SiPM during a time span. However, the results obtained suggest a threshold value of between around 20 and 60 microcells activated within a 1 ns time interval, but further tests are needed in order to confirm or reject this. Of the two other approaches tried, the signal voltage model gave reasonable results for the values tested but in a rather indirect way. The other approach, describing the connection between DC noise and AC RMS noise in the receiving system gave results deviating between 40% and 320% from the lab results, i.e. not so good match. / LiDAR är en fjärranalysteknik som använder laser för att kartlägga ett geografiskt område. Med flertalet användningsområden, bland annat inom industrin för självstyrande fordon, är LiDAR ett växande teknik- och forskningsområde. Kisel-fotomultiplikatorn är en halvledarapparat som ofta används i LiDAR-mottagarsystemet. Bakgrundsljus från omgivningen detekteras dock också av fotodetektorn vilket orsakar  brus i mottagarsystemet. Detta arbete syftar till att testa metoder för hur prestandan hos en 1D LiDAR med en kisel-fotomultiplikator i mottagaren kan estimeras, i en viss nivå av bakgrundsljus, med en viss målreflektans på ett visst mätavstånd. Detta utfördes genom att arbeta med matematiska modeller och jämföra dess resultat med resultat från laborativa tester på en viss LiDAR-modell. Det visade sig vara svårt att beskriva prestandan för denna LiDAR enligt en modell baserad på fotonflöde, huvudsakligen på grund av den okända kopplingen mellan tröskelnivån i termer av voltsignal i mottagarkretsen då tidmätningen stoppas och antalet aktiverade mikroceller i kisel-fotomultiplikatorn under ett visst tidsintervall. De resultat som erhölls visar dock på en träskelnivå någonstans mellan 20 och 60 mikroceller inom ett 1 ns tidsintervall, men ytterligare tester bör genomföras för att konfirmera eller förkasta detta. Av de övriga två angreppssätten prövade, gav modellen baserad på voltsignal rimliga resultat för värdena testade men på ett relativt indirekt sätt. Försök till beskrivning av sambandet mellan DC brus och AC RMS brus i mottagarsystemet gav resultat med mellan 40% och 320% avvikelse från de laborativa mätningarna, relativt dåligt alltså.

The mining industry uses vehicles for a wide range of applications, including excavation and transportation of rock and soil. Currently, this requires a lot of human labour, mainly drivers, but efforts are being made to increase automation, e.g. using autonomous vehicles. In order for a vehicle to reach any level of autonomy, it needs to be aware of its surroundings, for instance by using sensors. The placement of the sensors is a difficult problem. The goal of this project was to create a tool that would simplify the sensor placement process. The tool should simulate sensors on autonomous vehicles, both by visualizing their field of view and by generating synthetic data. The tool was created, including simulation environments, models of different types of sensors and tools to analyze the results of the simulation. Both the field of view visualization and the data analysis tools were shown to be powerful tools for evaluating sensor placements. All of the sensor models are able to generate data, with different levels of realism. The radar model and the camera model give a good estimation of what the sensors can detect, while the lidar model is capable of generating realistic data. / Gruvindustrin använder fordon till ett stort antal olika uppgifter, bland annat till att gräva ut och förflytta sten och jord. Detta kräver för tillfället mycket manuellt arbete, framförallt förare, men försök att automatisera delar av arbetet utförs, till exempel genom att använda autonoma fordon. För att ett fordon ska kunna bli autonomt krävs det att det kan känna av sin omgivning, exempelvis genom att använda sensorer. Sensorplacering är ett svårt problem. Målet med projektet var att skapa ett verktyg för att förenkla sensorplaceringsprocessen. Verktyget skulle simulera sensorer på autonoma fordon, både genom att visualisera deras synfält och genom att generera syntetisk data. Verktyget skapades, inklusive simuleringsmiljöer, modeller av olika typer av sensorer, och verktyg för att analysera genererad data. Både synfältsvisualiseringen och datagenereringen visades vara användbara verktyg för att utvärdera sensorplaceringar. Alla sensormodellerna kan generera data, med olika realistiska resultat. Radarmodellen och kameramodellen ger en bra uppskattning av vad sensorerna kan detektera, medan lidarmodellen kan generera realistisk data.

In this study, the weather impact on lidar signals has been researched. A lidar system was placed with a target at approximately 90 m and has together with a weather station collected data for about a year before this study. By using the raw detector data from the lidar, the full waveform can be obtained and the amplitude of the return pulse can be calculated. Atmospheric attenuation of lidar signals is often modeled using the lidar equation, which predicts an exponential decrease in energy over the distance. The factor in the exponent is referred to as the extinction coefficient and it is the main property studied in this thesis. By utilizing models for the extinction coefficient under different weather conditions, it is possible to simulate the performance of the lidar.  The extinction coefficient was calculated using different empirical models. The empirical models investigated in this thesis are the Kim and Kruse models for known visibility, the Al Naboulsi model for different types of fog with known visibility, the Carbonneau model for known precipitation amount in rainy conditions, and a similar model for snowy conditions. For the case of rain, a physical model was also used, which is derived through Mie theory. The physical model requires a particle size distribution, which is the number of particles of a certain radius per unit volume. A particle size distribution for rain was generated using the Ulbrich raindrop size distribution, using the precipitation amount recorded by the weather station. Particle size distributions for radiation and advection fog were also simulated.  The measured attenuation in lidar signals was compared to the predicted attenuation that was calculated using different models for the extinction coefficient in the lidar equation. Generally, the models tend to underestimate the amplitude of the return pulse. This can partially be explained by the assumptions used to derive the lidar equation, which neglects all augmentation of the beam. The visibility models gave more accurate results compared to the precipitation models. This was expected, since visibility is defined as a measure of attenuation and precipitation amount is not.  When a lidar signal is emitted, the light will be reflected from optical surfaces within the lidar and cause a pulse to be detected. This pulse is referred to as the zeropulse. In the first couple of meters of the transmission, we expect to see some backscattered light from adverse weather, since the detector has a larger solid angle at shorter distances. This returned light will be combined with the zeropulse and cause it to expand in width. By examining the zeropulse, it was possible to observe a difference between the average zeropulse under some different weather conditions. This leads to the conclusion that it may be possible to extract some information about current weather conditions from the zeropulse data, given that there is little ambient light and snowy weather conditions.  By integrating the zeropulse, variations in the shape of the zeropulse could be described by a single value. Then by separating the data into low and high visibility populations, the zeropulse integral could be used to predict the visibility. The conclusion was that the zeropulse integral can accurately predict whether visibility is above or below a threshold value, given that there is little ambient light and the visibility is known to be below 19950 m.