No description available.

The general theme running throughout this study is the enhancement of step functions which have been degraded by blur and/or additive noise in some form or another. We deal with step functions in both one and two dimensions. The two main areas of study are i. The enhancement of Synthetic Aperture Radar data. This is data which can be thought of some form of step function in two dimensions, and, ii. The enhancement of one dimensional step functions which have been degraded by both blur and additive noise. Although (i) is very specific to Synthetic Aperture Radar data (ii) is far more general and can be applied to any such data in this general category of steps. In fact a very wide range of problems can be thought of within the general context of being step-related. We describe and develop several methods is this study to deal with such problems.

No description available.

The hardware and software for a computer controlled optical radar, or lidar, system are described. The system builds on a previously installed pulsed ruby backscatter lidar, capable of acquiring data at controlled azimuth and elevation angles through the atmosphere. The described system replaces hardwired logic with computer control. Two coupled computers are used to allow a degree of real time control while data are processed. One of these computers reads and controls mount elevation angle, reads the laser energy monitor, and senses firing of the laser. The other computer serves as a user interface, and receives the lidar return data from a digitizer and memory, and the angle and energy information from the other computer. The second computer also outputs data to a disc drive. The software provided with the system is described, and the feasibility of additional software for both control and data processing is explored. Particular attention is given to data integrity and instrument and computer operation in the presence of the high energy pulses used to drive the laser. A previously described laser energy monitor has been improved to isolate it from laser transients. Mount elevation angles are monitored with an absolute angle readout. As a troubleshooting aid, a simulator with an output that approximates the lidar receiver output was developed. Its output is digitally generated and provides a known repetitive signal. Operating procedures are described for standard data acquisition, and troubleshooting is outlined. The system can be used by a relatively inexperienced operator; English sentences are displayed on the system console CRT terminal to lead the operator through data acquisition once the system hardware is turned on. A brief synopsis of data acquired on the system is given. Those data are used as the basis of other referenced papers. It constitutes soundings for over one hundred days. One high point has been operation of the system in conjunction with a balloon borne atmospheric particulate sampling package. The system has also been used occasionally as the transmitter of a lidar system with physically separated receiver and transmitter.

Bibliography: leaves 149-152.

The software system to process integrated slant path lidar data has been debugged, modified, documented, and improved in reliability and user-friendliness. The substantial data set acquired since 1979 has been processed and a large body of results has been generated. A database has been implemented to store, organize, and access the results. The lidar data set results--the S ratios, the optical depths, and the mixing layer heights are presented. The seasonal dependence of the lidar solution parameters has been explored. The assumptions made in the lidar solution procedure are investigated. The sensitivity of the S ratio and the particulate extinction coefficient to the system calibration constant is examined. The reliability of the calibration constant is demonstrated by examining the particulate to Rayleigh extinction ratio values above the mixing layer.

In this thesis we examine the issue regarding pricing of radar data and surveillance to the operators of air navigation service (ANS) at the aerodromes in Sweden. The question of who should be responsible for providing radar data to the operators is being managed that results in if it should be LFV, as it is today, the government or another authority. This is being examined since LFV in 2010 lost its monopoly position in the terminal area in Sweden. LFV still has monopoly on the en route part, and thru the en route income finances the radar data to all operators in Sweden. Air traffic service units (ATS) receive the radar data without any compensation to LFV, this needs to be regulated and conditions and prerequisites are necessary to be implemented. Our supervisor at LFV, Anders Andersson, has been the primary source of information regarding the current situation, background for the problem and also provided relevant documents with proper information. Laws and regulations have been accessed via the Swedish Transport Agency’s website and scientific articles on monopolies and pricing in aviation and other markets have been used in order to compare earlier issues similar to ours. The literature studies combined with interviews with Anders Andersson are the foundations of the development of the pricing schemes. The result of the thesis is presented as three different pricing schemes where each one of them are presented in tables and analysed how it will affect the ATS. In the first pricing scheme the cost for maintenance is equally divided between all ATS, this means every ATS has to pay the same cost regardless size of the airport, number of movement and net sales. The second pricing scheme is based on number of landings per year and divides the ATS in three categories. This scheme increases the cost with concern to the number of landings, which results in the larger ATS are charged more than the smaller ATS. The final pricing scheme is divided in four categories and based on terminal control area (TMA) and requirements on surveillance service. This means the different categories are based on a combination of the median distance flown in TMA and the different requirements the ATS must provide surveillance service. This pricing scheme is a disadvantage for the military airports and the ATS with associated TMA. The conclusions that can be made are the Swedish Transport Agency needs to implement some distinct guidelines and regulations regarding how the pricing should be made, where the pricing schemes and analysis in this thesis could form the basis for future investigations.

Weather is a major contributing factor in aviation accidents, incidents and delays. Doppler weather radar has emerged as a potent tool to observe weather. Aircraft carry an onboard radar but its range and angular resolution are limited. Networks of ground-based weather radars provide extensive coverage of weather over large geographic regions. It would be helpful if these data can be transmitted to the pilot. However, these data are highly voluminous and the bandwidth of the ground-air communication links is limited and expensive. Hence, these data have to be compressed to an extent where they are suitable for transmission over low-bandwidth links. Several methods have been developed to compress pictorial data. General-purpose schemes do not take into account the nature of data and hence do not yield high compression ratios. A scheme for extreme compression of weather radar data is developed in this thesis that does not significantly degrade the meteorological information contained in these data. The method is based on contour encoding. It approximates a contour by a set of systematically chosen ‘control’ points that preserve its fine structure upto a certain level. The contours may be obtained using a thresholding process based on NWS or custom reflectivity levels. This process may result in region and hole contours, enclosing ‘high’ or ‘low’ areas, which may be nested. A tag bit is used to label region and hole contours. The control point extraction method first obtains a smoothed reference contour by averaging the original contour. Then the points on the original contour with maximum deviation from the smoothed contour between the crossings of these contours are identified and are designated as control points. Additional control points are added midway between the control point and the crossing points on either side of it, if the length of the segment between the crossing points exceeds a certain length. The control points, referenced with respect to the top-left corner of each contour for compact quantification, are transmitted to the receiving end. The contour is retrieved from the control points at the receiving end using spline interpolation. The region and hole contours are identified using the tag bit. The pixels between the region and hole contours at a given threshold level are filled using the color corresponding to it. This method is repeated till all the contours for a given threshold level are exhausted, and the process is carried out for all other thresholds, thereby resulting in a composite picture of the reconstructed field. Extensive studies have been conducted by using metrics such as compression ratio, fidelity of reconstruction and visual perception. In particular the effect of the smoothing factor, the choice of the degree of spline interpolation and the choice of thresholds are studied. It has been shown that a smoothing percentage of about 10% is optimal for most data. A degree 2 of spline interpolation is found to be best suited for smooth contour reconstruction. Augmenting NWS thresholds has resulted in improved visual perception, but at the expense of a decrease in the compression ratio. Two enhancements to the basic method that include adjustments to the control points to achieve better reconstruction and bit manipulations on the control points to obtain higher compression are proposed. The spline interpolation inherently tends to move the reconstructed contour away from the control points. This has been somewhat compensated by stretching the control points away from the smoothed reference contour. The amount and direction of stretch are optimized with respect to actual data fields to yield better reconstruction. In the bit manipulation study, the effects of discarding the least significant bits of the control point addresses are analyzed in detail. Simple bit truncation introduces a bias in the contour description and reconstruction, which is removed to a great extent by employing a bias compensation mechanism. The results obtained are compared with other methods devised for encoding weather radar contours.

No description available.

Contract no. AF-33(615)-3227. Project DSR 76143.