title: Ameliorating Systematic Errors in Full-Field AMCW Lidar

authors: Godbaz, John Peter

subjects: Time of Flight

abstract: This thesis presents an analysis of systematic error in full-field amplitude modulated continuous wave range-imaging systems. The primary focus is on the mixed pixel/multipath interference problem, with digressions into defocus restoration, irregular phase sampling and the systematic phase perturbations introduced by random noise. As an integral part of the thesis, a detailed model of signal formation is developed, that models noise statistics not included in previously reported models.

Prior work on the mixed pixel/multipath interference problem has been limited to detection and removal of perturbed measurements or partial amelioration using spatial information, such as knowledge of the spatially variant scattering point spread function, or raytracing using an assumption of Lambertian reflection. Furthermore, prior art has only used AMCW range measurements at a single modulation frequency. In contrast, in this thesis, by taking multiple measurements at different modulation frequencies with known ratio-of-integers frequency relationships, a range of new closed-form and lookup table based inversion and bounding methods are explored. These methods include: sparse spike train deconvolution based multiple return separation, a closed-form inverse using attenuation ratios and a normalisation based lookup table method that uses a new property we term the characteristic measurement. Other approaches include a Cauchy distribution based model for backscattering sources which are range-diffuse, like fog or hair. Novel bounding methods are developed using the characteristic measurement and attenuation ratios on relative intensity, relative phase and phase perturbutation.

A detailed noise and performance analysis is performed of the characteristic measurement lookup table method and the bounding methods using simulated data. Experiments are performed using the University of Waikato Heterodyne range-imager, the Canesta XZ-422 and the Mesa Imaging Swissranger 4000 in order to demonstrate the performance of the lookup table method. The lookup table method is found to provide an order of magnitude improvement in ranging accuracy, albeit at the expense of ranging precision.

text: Ameliorating Systematic Errors in Full-Field AMCW Lidar This thesis presents an analysis of systematic error in full-field amplitude modulated continuous wave range-imaging systems. The primary focus is on the mixed pixel/multipath interference problem, with digressions into defocus restoration, irregular phase sampling and the systematic phase perturbations introduced by random noise. As an integral part of the thesis, a detailed model of signal formation is developed, that models noise statistics not included in previously reported models.

Prior work on the mixed pixel/multipath interference problem has been limited to detection and removal of perturbed measurements or partial amelioration using spatial information, such as knowledge of the spatially variant scattering point spread function, or raytracing using an assumption of Lambertian reflection. Furthermore, prior art has only used AMCW range measurements at a single modulation frequency. In contrast, in this thesis, by taking multiple measurements at different modulation frequencies with known ratio-of-integers frequency relationships, a range of new closed-form and lookup table based inversion and bounding methods are explored. These methods include: sparse spike train deconvolution based multiple return separation, a closed-form inverse using attenuation ratios and a normalisation based lookup table method that uses a new property we term the characteristic measurement. Other approaches include a Cauchy distribution based model for backscattering sources which are range-diffuse, like fog or hair. Novel bounding methods are developed using the characteristic measurement and attenuation ratios on relative intensity, relative phase and phase perturbutation.

A detailed noise and performance analysis is performed of the characteristic measurement lookup table method and the bounding methods using simulated data. Experiments are performed using the University of Waikato Heterodyne range-imager, the Canesta XZ-422 and the Mesa Imaging Swissranger 4000 in order to demonstrate the performance of the lookup table method. The lookup table method is found to provide an order of magnitude improvement in ranging accuracy, albeit at the expense of ranging precision.

year: 2012

title: Vicarious Traumatization in the Workplace: A Meta-Analysis on the Impact of Social Support

authors: Whitton, Melissa

subjects: Vicarious Traumatization

abstract: Healthy employees have been linked with decreased absenteeism, lower turnover, less accidents in the workplace, higher employee engagement and commitment, and greater employee resilience. However, there are many occupational hazards which can compromise the health of employees, leading to negative consequences for organisations and service users. Helping professionals are often exposed to indirect trauma through working with traumatised individuals. This puts them at risk of developing Vicarious Traumatisation, which can result in disruptions to schemas, depletion, symptoms of hyperarousal, avoidance, negative changes to cognition and mood, poor concentration, flashbacks and dreams, and intrusive thoughts or memories associated to the trauma of another. A professional will react differently in response to Vicarious Traumatic Exposure due to intrinsic features of the individual and multiple characteristics of the work being done. Therefore, whether Vicarious Traumatisation occurs depends on an interplay between both internal and external influences. The present study examined the impact of social support on the outcome of Vicarious Traumatisation by running a meta-analysis on 21 studies which analysed this relationship. Results showed that the overall effect size suggested a significant, yet small negative relationship between social support and the negative outcomes of Vicarious Traumatic Exposure. However, due to the I-squared value being so large, the significance of this relationship is questionable. Therefore, further analysis needs to occur to examine where this dispersion is occurring, either through moderator or subgroup analysis.

text: Vicarious Traumatization in the Workplace: A Meta-Analysis on the Impact of Social Support Healthy employees have been linked with decreased absenteeism, lower turnover, less accidents in the workplace, higher employee engagement and commitment, and greater employee resilience. However, there are many occupational hazards which can compromise the health of employees, leading to negative consequences for organisations and service users. Helping professionals are often exposed to indirect trauma through working with traumatised individuals. This puts them at risk of developing Vicarious Traumatisation, which can result in disruptions to schemas, depletion, symptoms of hyperarousal, avoidance, negative changes to cognition and mood, poor concentration, flashbacks and dreams, and intrusive thoughts or memories associated to the trauma of another. A professional will react differently in response to Vicarious Traumatic Exposure due to intrinsic features of the individual and multiple characteristics of the work being done. Therefore, whether Vicarious Traumatisation occurs depends on an interplay between both internal and external influences. The present study examined the impact of social support on the outcome of Vicarious Traumatisation by running a meta-analysis on 21 studies which analysed this relationship. Results showed that the overall effect size suggested a significant, yet small negative relationship between social support and the negative outcomes of Vicarious Traumatic Exposure. However, due to the I-squared value being so large, the significance of this relationship is questionable. Therefore, further analysis needs to occur to examine where this dispersion is occurring, either through moderator or subgroup analysis.

year: 2018

title: Policy for Maori: values, assumptions and closing the gap

authors: Levy, Michelle Patricia

subjects: Maori

abstract: This paper looks at the issue of what it is about the way in which policy is developed which
influences whether or not policy meets the needs of Maori. To do this I will focus on one component
of policy making; the role of the values and assumptions of policy makers. Assumptions about the
nature of policy making and the way in which policy can be used to maintain and modify norms and
standards, determine values and define problems are briefly investigated. These issues are
highlighted using the Code of Family and Social Responsibility as an example of the way in which
dominant cultural value bases and assumptions have influenced the way in which policy issues are
framed and presented. The paper concludes by asking why the consideration of the values of policy
makers is important for Maori and how can I, as a Maori policy analyst working within the
Government policy making sector, contribute to the development of policy which is based on Maori
assumptions, realities, values and world views.

text: Policy for Maori: values, assumptions and closing the gap This paper looks at the issue of what it is about the way in which policy is developed which
influences whether or not policy meets the needs of Maori. To do this I will focus on one component
of policy making; the role of the values and assumptions of policy makers. Assumptions about the
nature of policy making and the way in which policy can be used to maintain and modify norms and
standards, determine values and define problems are briefly investigated. These issues are
highlighted using the Code of Family and Social Responsibility as an example of the way in which
dominant cultural value bases and assumptions have influenced the way in which policy issues are
framed and presented. The paper concludes by asking why the consideration of the values of policy
makers is important for Maori and how can I, as a Maori policy analyst working within the
Government policy making sector, contribute to the development of policy which is based on Maori
assumptions, realities, values and world views.

year: 1999