Map-Based Localization for Unmanned Aerial Vehicle Navigation

Unmanned Aerial Vehicles (UAVs) require precise pose estimation when navigating in indoor and GNSS-denied / GNSS-degraded outdoor environments. The possibility of crashing in these environments is high, as spaces are confined, with many moving obstacles. There are many solutions for localization in GNSS-denied environments, and many different technologies are used. Common solutions involve setting up or using existing infrastructure, such as beacons, Wi-Fi, or surveyed targets. These solutions were avoided because the cost should be proportional to the number of users, not the coverage area. Heavy and expensive sensors, for example a high-end IMU, were also avoided. Given these requirements, a camera-based localization solution was selected for the sensor pose estimation. Several camera-based localization approaches were investigated. Map-based localization methods were shown to be the most efficient because they close loops using a pre-existing map, thus the amount of data and the amount of time spent collecting data are reduced as there is no need to re-observe the same areas multiple times. This dissertation proposes a solution to address the task of fully localizing a monocular camera onboard a UAV with respect to a known environment (i.e., it is assumed that a 3D model of the environment is available) for the purpose of navigation for UAVs in structured environments. Incremental map-based localization involves tracking a map through an image sequence. When the map is a 3D model, this task is referred to as model-based tracking. A by-product of the tracker is the relative 3D pose (position and orientation) between the camera and the object being tracked. State-of-the-art solutions advocate that tracking geometry is more robust than tracking image texture because edges are more invariant to changes in object appearance and lighting. However, model-based trackers have been limited to tracking small simple objects in small environments. An assessment was performed in tracking larger, more complex building models, in larger environments. A state-of-the art model-based tracker called ViSP (Visual Servoing Platform) was applied in tracking outdoor and indoor buildings using a UAVs low-cost camera. The assessment revealed weaknesses at large scales. Specifically, ViSP failed when tracking was lost, and needed to be manually re-initialized. Failure occurred when there was a lack of model features in the cameras field of view, and because of rapid camera motion. Experiments revealed that ViSP achieved positional accuracies similar to single point positioning solutions obtained from single-frequency (L1) GPS observations standard deviations around 10 metres. These errors were considered to be large, considering the geometric accuracy of the 3D model used in the experiments was 10 to 40 cm. The first contribution of this dissertation proposes to increase the performance of the localization system by combining ViSP with map-building incremental localization, also referred to as simultaneous localization and mapping (SLAM). Experimental results in both indoor and outdoor environments show sub-metre positional accuracies were achieved, while reducing the number of tracking losses throughout the image sequence. It is shown that by integrating model-based tracking with SLAM, not only does SLAM improve model tracking performance, but the model-based tracker alleviates the computational expense of SLAMs loop closing procedure to improve runtime performance. Experiments also revealed that ViSP was unable to handle occlusions when a complete 3D building model was used, resulting in large errors in its pose estimates. The second contribution of this dissertation is a novel map-based incremental localization algorithm that improves tracking performance, and increases pose estimation accuracies from ViSP. The novelty of this algorithm is the implementation of an efficient matching process that identifies corresponding linear features from the UAVs RGB image data and a large, complex, and untextured 3D model. The proposed model-based tracker improved positional accuracies from 10 m (obtained with ViSP) to 46 cm in outdoor environments, and improved from an unattainable result using VISP to 2 cm positional accuracies in large indoor environments. The main disadvantage of any incremental algorithm is that it requires the camera pose of the first frame. Initialization is often a manual process. The third contribution of this dissertation is a map-based absolute localization algorithm that automatically estimates the camera pose when no prior pose information is available. The method benefits from vertical line matching to accomplish a registration procedure of the reference model views with a set of initial input images via geometric hashing. Results demonstrate that sub-metre positional accuracies were achieved and a proposed enhancement of conventional geometric hashing produced more correct matches - 75% of the correct matches were identified, compared to 11%. Further the number of incorrect matches was reduced by 80%

MODELING AND EVALUATION OF ALTERNATIVE INFORMATION SYSTEM STRUCTURESi

A general graphic model for organizational information systems (IS) is proposed. The model includes generalized decision making and data manipulation functions to regulate generalized organizational processes through flows of information. The general IS model serves as a basic pattern to approach the design of any IS. In particular, alternative IS strudures or designs can be derived from the model. Structures include not only information that will be computerized but also the prescription of the decision making behavior of the information users. The existence of alternatives leads to a problem of evaluation for which a quantitative modeling approach is proposed

The Mathematization of Macroeconomics: A Recursive Revolution

Frank Ramsey's classic framing of the dynamics of optimal savings, [51] as one to be solved as a problem in the calculus of variations and Ragnar Frisch's imaginative invoking of a felicitous Wicksellian metaphor to provide the impulse-propagation dichotomy, in a stochastic dynamic framework, for the tackling the problem of business cycles [17], have come to be considered the twin fountainheads of the mathematization of macroeconomics in its dynamic modes - at least in one dominant tradition. The intertemporal optimization framework of a rational agent, viewed as a signal processor, facing the impulses that are propagated through the mechanisms of a real economy, provide the underpinnings of the stochastic dynamic general equilibrium (SDGE) model that has become the benchmark and frontier of current macroeconomics. In this paper, on the 80th anniversary of Ramsey's classic and the 75th anniversary of Frisch's Cassel Festschrift contribution, an attempt is made to characterize the mathematization of macroeconomics in terms of the frontier dominance of recursive methods. There are, of course, other - probably more enlightened - ways to tell this fascinating story. However, although my preferred method would have been to tell it as an evolutionary development, since I am not sure that where we are represents progress, from where we were, say 60 years ago, I have chosen refuge in some Whig fantasies.Macrodynamics, Mathematical Economics, Dynamic Economics, Computational Economics.

A preliminary design and implementation of the low-thrust simulation and trajectory search program (LOWTRAJ)

The results are presented of one phase of research conducted for the JPL Solar Electric Propulsion (SEP) Navigation Software System development program. It deals only with the problem of designing the flight quality trajectory program, which is a major subset of the entire navigation software system. In this phase of research (breadboard development phase), attempts were made to assess the SEP trajectory software functional requirements, to investigate the program design method satisfying these requirements, to identify the primary anticipated problem areas, and to provide solutions to these problem areas. These efforts culminated in the development of a compact breadboard program. A functional description and the mathematical formulation of the program are presented

Tropical deep convective cloud morphology

2014 Fall.Includes bibliographical references.A cloud-object partitioning algorithm is developed. It takes contiguous CloudSat cloudy regions and identifies various length scales of deep convective clouds from a tropical, oceanic subset of data. The methodology identifies a level above which anvil characteristics become important by analyzing the cloud object shape. Below this level in what is termed the pedestal region, convective cores are identified based on reflectivity maxima. Identifying these regions allows for the assessment of length scales of the anvil and pedestal of the deep convective clouds. Cloud objects are also appended with certain environmental quantities from the ECMWF reanalysis. Simple geospatial and temporal assessments show that the cloud object technique agrees with standard observations of local frequency of deep-convective cloudiness. Additionally, the nature of cloud volume scale populations is investigated. Deep convection is seen to exhibit power-law scaling. It is suggested that this scaling has implications for the continuous, scale invariant, and random nature of the physics controlling tropical deep convection and therefore on the potentially unphysical nature of contemporary convective parameterizations. Deep-convective clouds over tropical oceans play important roles in Earth's climate system. The response of tropical, deep convective clouds to sea surface temperatures (SSTs) is investigated using this new data set. Several previously proposed feedbacks are examined: the FAT hypothesis, the Iris hypothesis, and the Thermostat hypothesis. When the data are analyzed per cloud object, each hypothesis is broadly found to correctly predict cloud behavior in nature, although it appears that the FAT hypothesis needs a slight modification to allow for cooling cloud top temperatures with increasing SSTs. A new response that shows that the base temperature of deep convective anvils remains approximately constant with increasing SSTs is introduced. These cloud-climate feedbacks are integrated to form a more comprehensive theory for deep convective anvil responses to SST. An investigation into the physical shape and size of mature, oceanic, tropical, deep convective clouds is conducted. Mean cloud objects are discussed. For single-core clouds, the mean cloud has an anvil width of 95 km, a pedestal width of 11 km, and an anvil thickness of 6.4 km. The number of identified convective cores within pedestal correlates well with certain length scales and morphological attributes of cloud objects. As the number of cores increases, so does the size of the mean cloud object. Pedestal width is shown to regress linearly to anvil width when a 2/3rd power scaling is applied to pedestal width. This result implies continuous but retarded growth of anvils with growing pedestals and equivalence in the mass flux convecting through the pedestal and into the anvil. Trends in cloud scales with cloud base and top heights are investigated to shed light on related convective parameterization assumptions and on convective transport, respectively. Many of the results obtained using the CloudSat methodology are also examined with a large-domain radiative-convective equilibrium numerical simulation and are found to exhibit similar trends when modeled. Finally, various CloudSat sampling issues are discussed in several appendices. Utilizing the CloudSat cloud object database, an examination of the sensitivity of oceanic, mature, deep convective cloud morphology to environmental characteristics is conducted. Convective available potential energy (CAPE), aerosol optical depth, mid-level vertical velocity, and troposphere deep shear are all included as meteorological measures. The sensitivity of various aspects of convective morphology to each one of these environmental characteristics is assessed individually. The results demonstrate that clouds tend to be invigorated by higher CAPE, aerosol amount, and upward mid-level vertical velocity. Stronger shear tends to make clouds wider but also shallower. The relative importance of each of these, and some additional, environmental measures to trends in cloud morphology are compared. It is found that aerosol, mid-level vertical velocity, and sea surface temperature tend to be the most influential environmental characteristics to convective morphology. The results are shown to be insensitive to the manner in which the environment is measured. The potentially surprising insensitivity of cloud morphology to CAPE is discussed in detail