Philip Collier

A generalized model of decision‐making processes for companies in financial distress

Decisions by insolvency experts are vital to the future of a company in financial difficulties and impact the financial returns to creditors and other stakeholders. This paper describes a generalized model of the decision-making processes used by insolvency experts when dealing with companies in financial distress. The model includes identification of high-level factors that are important in making insolvency decisions and how these factors are used in the decision-making processes of insolvency experts. In particular, financial and non-financial factors are required for judgments about relevant stakeholders and the future of a company. Validation experiments show a high degree of conformance between the model and a variety of actual cases.

Distortion modelling and the transition to GDA94

As users and managers of spatial information face the adoption of the new Geocentric Datum of Australia (GDA94), the need for a simple, comprehensive and unique transformation process has emerged as an urgent requirement. Such a transformation process must incorporate distortion modelling in order to take full advantage of the new datum, thereby offering the potential to improve the accuracy of existing spatial data. This paper presents the need for distortion modelling and an investigation and evaluation of various options.

Modelling geoid undulations with an artificial neural network

Examines the use of a backpropagation neural network to model geoid undulations. Modelling of the Earths gravity field, and in particular the separation between ellipsoid and geoid surface, is one of the fundamental problems in the field of geodesy. Geoid undulations are important for relating heights derived from the satellite based Global Positioning System to orthometric heights, which determine the flow of water. Modelling of geoid undulations has been traditionally done using Stokes integral, least squares collocation, or by fast Fourier transforms. The paper presents the results of preliminary investigations which suggest the backpropagation neural network provides a useful tool for geoid undulation modelling.

Mitigation of periodic GPS multipath errors using a normalised least mean square adaptive filter

A field trial over a period of four days has been conducted to investigate the impact of multipath in a highly obstructed environment and the capability of a Least Mean Square (LMS) adaptive filter to model and thereby reduce its effect. The multipath component of the GPS observations has been isolated by computing the double difference carrier phase residuals. Because multipath errors are a function of the satellite‐receiver geometry, the resulting daily time series show a repeated pattern of multipath contamination. The numerical analysis presented here demonstrates that adaptive filtering is able to identify and remove these repeated multipath errors. Besides a detailed description of the experimental procedure and the filtering results, a brief summary is also given of the theoretical background for the LMS adaptive filter.

GPS DEFLECTION MONITORING OF THE WEST GATE BRIDGE

The achievable precision and relatively high sampling rates of currently available GPS receivers are well suited for monitoring the movements of long-span engineering structures where the amplitude of movements is often more than a few centimetres and the frequency of vibrations is low (below 10 Hz). However, engineering structures often offer non-ideal environments for GPS data collection due to high multipath interference and obstructions causing cycle slips in the GPS observations. Also, for many engineering structures such as bridge decks, vertical movements are more pronounced and more structurally critical than horizontal movements. Accuracy of GPS determined positions in the vertical direction is typically two to three times poorer than in the horizontal component. This paper describes the results of a GPS deflection monitoring trial on the West Gate Bridge in Melbourne, Australia. The results are compared to the estimated frequencies and movements from the design of the bridge and previous accelerometer campaigns. The frequency information derived from the GPS results is also compared to frequency data extracted from an accelerometer installed close to a GPS receiver. GPS results agree closely to the historical results and recent accelerometer trials for key modal frequencies. This indicates the suitability of GPS receivers to monitor engineering structures that exhibit smaller movements due to their stiffness and in environments not ideally suited to using GPS.

A New Approach to Delineating the Littoral Zone for an Australian Marine Cadastre

Abstract The vast majority of boundaries within the littoral zone are based on one of the many possible tidal lines. These tidal lines are defined by the line of intersection between a particular tidal datum and the land mass. The difficulty with boundaries defined on the basis of a tidal datum is that the rigorous and consistent realisation of the line of intersection between a nominated tidal datum and the land mass is notoriously difficult, creating spatial uncertainty and the potential for conflict and dispute. This paper describes and discusses some fundamental issues in defining and realising tidal lines, with particular interest in their relevance and application to the development of a marine cadastre. A technical solution for realising the line of intersection between any given tidal datum and the foreshore terrain is presented. Particular attention is paid to the modelling of the water and terrain surfaces as the two fundamental datasets required for the intersection computations. The methodology and results of a case study in New South Wales, Australia, are presented, along with some initial findings.

Dynamic network adjustment and the transition to GDA94

As Australia faces the adoption of a new geodetic datum the question of how best to undertake the transition to that datum naturally arises. Without doubt the most comprehensive transformation strategies will require extensive re-adjustment of vast volumes of survey control data. This is true whether considering transformation of the survey control data itself or in the preparation of distortion models for the transformation of compiled data stored in spatial information systems. In light of the size of the transition task it is likely there will be more adjustments carried out in the next few years than previously required. The obvious need is for a process to consistently undertake the necessary adjustments in a rigorous and efficient manner. A newly developed technique known as Dynamic Network Adjustment offers the potential to satisfy this need and to maintain these networks once the initial readjustments have been completed.

Assessing and reporting real‐time data quality for GNSS reference stations

Real‐time positioning, based on CORS network technology, is becoming a routine operation within and outside the spatial industry. The expanding user base and diverse range of applications employing this technology can impose significant expectations on the providers of network RTK services. As a consequence, there is a pressing need to supply network operators with dependable, real‐time information regarding data quality. This paper addresses the question of how to assess the real‐time performance of CORS stations by means of comparison against a historical data archive, along with a discussion on intelligent alerting of network operators when noteworthy quality breaches occur.

A GDA94 transformation grid for Tasmania

As Australia moves towards the adoption of the new Geocentric Datum of Australia (GDA94), each State and Territory will have to implement a process for the transformation of digital spatial data. Using a detailed distortion model, the Tasmanian Office of the Surveyor General has developed a transformation grid that will allow data to be moved from the current to the new datum in a simple, accurate and efficient manner.

Options and strategies for transition to GDA94

The adoption of a new geocentric datum in Australia has been recently proposed. In accepting this proposal. options for making the transition to the new datum will need to be carefully considered. Spatial data can take various forms. ranging from survey control networks through to plans. maps and digital geographic information systems. All such spatial data will have to be related to the new datum when and if that datum Is adopted. This paper presents some of the options for transforming spatial data to the new Geocentric Datum of Australia.