Utilizing both Assisted GPS (A-GPS) techniques and new high-sensitivity embedded GPS hardware, mobile phones are now able to achieve positioning in harsh environments such as urban canyons and indoor locations where older embedded GPS chips could not. This paper presents an empirical analysis of the positional accuracy of location data gathered using a high-sensitivity GPS-enabled mobile phone. The performance of the mobile phone is compared to that of regular recreational grade GPS receivers. Availability of valid GPS position fixes on the mobile phones tested was consistently close to 100% both outdoors and indoors. During static outdoor testing, positions provided by the mobile phones revealed a median horizontal error of between 5·0 and 8·5 m, substantially larger than those for regular autonomous GPS units by a factor of 2 to 3. Horizontal errors during static indoor testing were larger compared to outdoors, but the difference in accuracy between mobile phones and regular GPS receivers was reduced. Despite the modest performance of A-GPS on mobile phones, testing under various conditions revealed that very large errors are not very common. The maximum horizontal error during outdoor testing never exceeded 30 metres and during indoor testing never exceeded 100 metres. Combined with the relatively consistent availability of valid GPS position fixes under varying conditions, the current study has confirmed the reliability of A-GPS on mobiles phones as a source of location information for a range of different LBS applications.

Cooperative positioning (CP) is a localization technique originally developed for use across wireless sensor networks. With the emergence of Dedicated Short Range Communications (DSRC) infrastructure for use in Intelligent Transportation Systems (ITS), CP techniques can now be adapted for use in location determination across vehicular networks. In vehicular networks, the technique of CP fuses GPS positions with additional sensed information such as inter-vehicle distances between the moving vehicles to determine their location within a neighbourhood. This paper presents the results obtained from a research study undertaken to demonstrate the capabilities of DSRC for meeting the positioning accuracies of road safety applications. The results show that a CP algorithm that fully integrates both measured/sensed data as well as navigation information such as map data can meet the positioning requirements of safety related applications of DSRC (<0·5 m). This paper presents the results of a Cramer Rao Lower Bound analysis which is used to benchmark the performance of the CP algorithm developed. The Kalman Filter (KF) models used in the CP algorithm are detailed and results obtained from integrating GPS positions, inter-vehicular ranges and information derived from in-vehicle maps are then discussed along with typical results as determined through a variety of network simulation studies.

The Global Positioning System (GPS) is unreliable in dense urban areas, known as urban canyons, which have tall buildings or narrow streets. This is because the buildings block the signals from many of the satellites. Combining GPS with other Global Navigation Satellite Systems (GNSS) significantly increases the availability of direct line-of-sight signals. Modelling is used to demonstrate that, although this will enable accurate positioning along the direction of the street, the positioning accuracy in the cross-street direction will be poor because the unobstructed satellite signals travel along the street, rather than across it. A novel solution to this problem is to use 3D building models to improve cross-track positioning accuracy in urban canyons by predicting which satellites are visible from different locations and comparing this with the measured satellite visibility to determine position. Modelling is used to show that this shadow matching technique has the potential to achieve metre-order cross-street positioning in urban canyons. The issues to be addressed in developing a robust and practical shadow matching positioning system are then discussed and solutions proposed.

The routes of young, inexperienced pigeons released at four sites up to 13·5 km from the loft were recorded with GPS-based tracking devices. The routes were found to differ from those of old, experienced pigeons in several aspects: (1) Although being oriented when departing, young birds show more scatter and larger deviations from the home direction, but usually restrict their flights to a semicircle. (2) They apparently ignore prominent landmarks near the loft that are clearly visible. (3) Their tracks are typically more complex, consisting of a number of distinctive phases where the young birds head in different directions, which results in significantly longer routes, often exceeding the direct home distances more than four times. (4) At the same time, young birds seldom venture further away from the release site than the direct distance to home. Their behaviour can be interpreted as exploration to obtain new information on the distribution of navigational factors to be included in their still rudimentary navigational ‘map’. At the same time, their flights seem to include elements of safety, like anchoring the flights around the release site and a sense of distance, which help to reduce the chance of getting lost.

Current strategic plans for air traffic management (ATM) envisage a transition from radar control to a trajectory-based system. The future ATM concepts are very different in a great number of aspects from the present system. The focus here is on the design of safe systems, in particular the appropriate air traffic control (ATC) separation minima. This Part 1 sketches the historical origins of ATC separation minima and then analyses the safety thinking behind current minima and the issues involved in risk modelling. Why have the critical minima largely remained unchanged for several decades – stasis? Part 2 then addresses key safety issues in the transition to the new ATM concept.

‘Give me a lever long enough and a fulcrum on which to place it, and I shall move the world.’ Archimedes.

A dynamic state realization for tightly coupling Global Positioning System (GPS) measurements with an Inertial Navigation System (INS) is described. The realization, based on the direct fusion of GPS and INS systems through Kalman filter state dynamics, explicitly accounts for temporal and spatial decorrelation of GPS measurement errors (such as tropospheric, ionospheric, and multipath errors) through state augmentation, thereby ensuring Kalman filter integrity under fault-free error conditions. Predicted system performance for a Local Area Augmentation System (LAAS) aircraft precision approach application is evaluated using covariance analysis and validated with flight data.

Built-in fault detection mechanisms based on the Kalman filter innovations are also evaluated to help provide integrity under certain fault conditions. It is shown that an algorithm based on the integral of Kalman filter innovations outperforms other existing GPS fault detection methods in the detection of slowly developing ranging errors, such as those caused by ionospheric and tropospheric anomalies.

In our paper The Risk Homeostasis Theory1, it was accepted that the behaviour of people involved in the operation of cargo carrying ships is conditioned to maximize the economic benefits of the amount of risk assumed in the transport. As a follow-up to that paper, the objective of this one is to investigate the relationship between the level of compliance of the cargo carrying vessels with international standards and the degree of severity of the incidents they are involved in. For this purpose, we analyse the same sample of 2,584 cargo carrying ships involved in incidents during 2005 and 2006 used in that investigation. The variables of the Paris MoU to identify substandard ships are used again to measure the standard level of ships and the degree of seriousness of incidents is determined by the number of days ships are under repair.

Human watch-keeping is necessary to prevent incidents at sea such as groundings and collisions. For many years, electronic aids to navigation have been utilised in watch-keeping but, with electronic marine systems becoming more sophisticated, the part they play in preventing collisions and groundings should become increasingly important. However, this article uses secondary data from the Safety Digest for 2008 compiled by the Marine Accident Investigation Bureau of the United Kingdom; eight case studies are used to show that electronic marine systems, whether integrated or not, are still playing a part in poor watch-keeping resulting in collisions, near misses and groundings. Primary data from fishing skippers of British based vessels have been used to confirm the findings from the secondary data that poor watch-keeping is often the cause of not keeping a proper lookout and that the watch-keeper has a too heavy reliance on the electronic aids. Brief suggestions are made as to how the electronic aids may be adapted to overcome these problems and thus to support the watch-keeper.

The paper presents the Bering Sea ice cover data referring to the period from 1998/9 to 2007/8. Vessels' operational problems in that area are indicated. The traffic is discussed, with vessels divided into two basic groups. The authors attempt to explain why ice covers mainly the eastern and northern part of the sea and define the maximum ice extent in the decade under consideration. This study is based on selected data available on the website of the National Ice Center [6].

In this paper, formulae drawn from the discipline of map projections are applied to provide simple and accurate solutions for the Inverse and Direct problems on the Great Ellipse. Distance along the meridional arc of the spheroid as a function of geodetic latitude is defined in terms of an elliptic integral which will be replaced here with a compact harmonic series approximation possessing simplicity and high accuracy. Latitude as a function of distance along the meridional arc will also be obtained via another equally simple inversion series that also possesses high accuracy. When these two series are applied with their constants modified to suit the section ellipse, they will be shown to provide accurate solutions to the inverse and direct navigation problems pertaining to the Great Ellipse, and thereby provide a complete solution that is also simple to implement.