This paper reviews the use of the air for the police in their operations to fight crime throughout the UK. There is a description of the job of the aircrew, the role and navigation systems and the aircraft used in daily operations. There is an examination of the use of both the helicopter and fixed wing aircraft concentrating on their suitability for police operations in which the weather and cost constraints are seen to be major factors to be considered in striking the balance to obtain the best effectiveness.

This paper describes the United States Coast Guard's efforts regarding Long Range Identification & Tracking (LRIT) of ships. Among those elements included in the LRIT plan, automatic identification systems (AIS), typically envisioned as a short-range system, may also play a long-range role. AIS vessel tracking may be accomplished through high elevation shore sites allowing reception of AIS signals to nominally 24 nm that loosely puts it in the category of a short-range sensor. Additionally, the US Coast Guard is conducting research and development efforts to determine the feasibility of using AIS receive capability on low earth orbit (LEO) satellites and high altitude, long endurance (HALE) airships or balloons. In parallel with the developing technical capabilities, the US approach with the International Maritime Organization (IMO), and domestic legislation and regulations are also addressed. Finally, a vision for the implementation of LRIT is offered. The paper was presented on 9 November 2004 at Church House, London during the Institute's NAV 04 Conference.

This paper was the basis of a presentation given on 9 November 2004 at Church House, London during the Institute's NAV 04 Conference. The author argues that AIS has been proven as a valuable aid to safe navigation, but requires comprehensive training to ensure its proper and effective use. Furthermore, he supports those concerned that using AIS in support of “homeland security” will make ships more vulnerable to attack.

Automatic Identification System (AIS) has recently become the leading issue in maritime navigation and traffic management worldwide. The present AIS solution, based on a VHF data communications scheme, provides AIS functionalities for SOLAS (AIS Class A) vessels only in a limited environment defined by radio propagation properties. Here we present a novel approach in AIS development based on current mobile communication technologies. It utilises existing mobile communications equipment that the majority of targetted end-users own and are familiar with. A novel AIS concept aims to offer a transition of AIS data traffic to mobile Internet. An innovative AIS architecture supports AIS data processing, storing and transferring to authorised parties. This enhances not only the operational area, but also provides the global AIS with data transfer security and an improved aids-for-navigation service, with all legally traceable vessels (both AIS Class A and AIS Class B) included in the system. In order to provide the development framework for Internet AIS, a set of essential four use-cases, a communication protocol and the first Internet AIS prototype have been recently developed and are briefly introduced in this article.

In general, a Reference Station calculates differential corrections which are valid for that exact location (zero baseline) at that particular epoch (age of corrections zero). However, DGPS users may be located as far as 200 nm away from the Reference Station and some of the errors compensated for by the Reference Station vary with space, namely satellite ephemeris, tropospheric and ionospheric errors. Therefore, the corrections calculated at the Reference Station suffer certain accuracy degradation as the separation distance increases, because of a decreasing relevance of the Reference Station data to the user. The error growth with increasing distance to the beacon is accentuated by the inability of Reference Station and user to see the same satellites, commonly termed the lack of intervisibility. The error growth with distance is the most important factor determining DGPS accuracy, but surprisingly very little has been done to assess it. US official documents and IALA state that the achievable accuracy degrades at an approximate rate of 1 m for each 150 km (80 nm) distance from the broadcast site, but this value is based on a theoretical prediction, made back in 1993. To estimate the error growth with real data, 6 DGPS receivers were placed along the Portuguese coastline at approximately 50 nm intervals from Sagres Broadcast Station, in a South – North direction. This paper describes the results of the trial.

The Disaster Monitoring Constellation (DMC) is an international Earth observation programme to provide a rapid global remote sensing service for the monitoring and mitigation of natural and man-made disasters. Although the Global Positioning System (GPS) was originally designed for terrestrial and air applications, satellite operations have benefited greatly from the use of on-board GPS receivers. This paper describes the GPS receiver operations on the DMC satellites, performance analysis, lessons learned, and upgrades planned for the future.

Extensive ionospheric scintillation and Total Electron Content (TEC) data were collected by the Institute of Engineering Surveying and Space Geodesy (IESSG) in Northern Europe during years of great impact of the solar maximum on GNSS users (2001–2003). The ionospheric TEC is responsible for range errors due to its time delay effect on transionospheric signals. Electron density irregularities in the ionosphere, occurring frequently during these years, are responsible for (phase and amplitude) fluctuations on GNSS signals, known as ionospheric scintillation. Since June 2001 four GPS Ionospheric Scintillation and TEC Monitor receivers (the NovAtel/AJ Systems GSV4004) have been deployed at stations in the UK and Norway, forming a Northern European network, covering geographic latitudes from 53° to 70° N approximately. These receivers compute and record GPS phase and amplitude scintillation parameters, as well as TEC and TEC variations. The project involved setting up the network and developing automated archiving and data analysis strategies, aiming to study the impact of scintillation on DGPS and EGNOS users, and on different GPS receiver technologies. In order to characterise scintillation and TEC variations over Northern Europe, as well as investigate correlation with geomagnetic activity, long-term statistical analyses were also produced. This paper summarises our findings, providing an overview of the potential implications of ionospheric scintillation for the GNSS user in Northern Europe.

Map Matching (MM) algorithms are usually employed for a range of transport telematics applications to correctly identify the physical location of a vehicle travelling on a road network. Two essential components for MM algorithms are (1) navigation sensors such as the Global Positioning System (GPS) and dead reckoning (DR), among others, to estimate the position of the vehicle, and (2) a digital base map for spatial referencing of the vehicle location. Previous research by the authors (Quddus et al., 2003; Ochieng et al., 2003) has developed improved MM algorithms that take account of the vehicle speed and the error sources associated with the navigation sensors and the digital map data previously ignored in conventional MM approaches. However, no validation study assessing the performance of MM algorithms has been presented in the literature. This paper describes a generic validation strategy and results for the MM algorithm previously developed in Ochieng et al. (2003). The validation technique is based on a higher accuracy reference (truth) of the vehicle trajectory as determined by high precision positioning achieved by the carrier-phase observable from GPS. The results show that the vehicle positions determined from the MM results are within 6 m of the true positions. The results also demonstrate the importance of the quality of the digital map data to the map matching process.

Map matching has been widely applied in car navigation systems as an efficient method to display the location of vehicles on maps. Various map-matching algorithms have been proposed. Inevitably, the correctness of the map matching is closely related to the accuracy of positioning sensors, such as GPS or Dead Reckoning (DR), and the complexity of the road network and map, especially in urban areas where the GPS signal may be constantly blocked by buildings and the road network is complicated. The existing map matching algorithms cannot resolve the positioning problems under all circumstances. They sometimes give the wrong position estimates of the car on road; the result is called mismatching. In order to improve the quality of map matching, a deep understand of the accuracy of sensor errors on mismatching is important. This paper analyses various factors that may affect the quality of map matching based on extensive tests in Hong Kong. Suggestions to improve the success rate of map matching are also provided.

The paper discusses the development of an adaptive Kalman filter for pipeline surveying applications. Various measurement models are developed and numerically tested using a real natural gas pipeline dataset. Since, for tactical-grade IMUs, odometer-derived velocity measurements alone cannot yield good results, two non-holonomic constraints are augmented to make the three-direction measurement model. Smoothing computation is also applied to yield the best trajectory using all the information contained in the past, current and future measurements. The trajectory errors are within 10–20 m for extreme cases, and within 10 m for most cases. RMS of the trajectory errors is expected to be about 2·5 m.

The objective of this paper is to describe recent progress in the area of the Ground Based Augmentation System (GBAS) σpr_gnd establishment to ensure aircraft precision approach navigation integrity. In particular, this paper details: (1) the development and testing of a new adaptive binning algorithm for processing GBAS reference station empirical data to account for ranging error non-stationarity; (2) an introduction of a practical empirical method to quantify and compensate for the effects of seasonal variations of ranging error; and (3) the synthesis of these empirical results with existing theoretical ground-multipath models toward a quantitative establishment σpr_gnd for GBAS.

In this paper, a simplified and direct computation method formulated by the fixed coordinate system and relative meridian concept in conjunction with vector algebra is developed to deal with the classical problems of celestial navigation. It is found that the proposed approach, the Simultaneous Equal-altitude Equation Method (SEEM), can directly calculate the Astronomical Vessel Position (AVP) without an additional graphical procedure. The SEEM is not only simpler than the matrix method but is also more straightforward than the Spherical Triangle Method (STM). Due to tedious computation procedures existing in the commonly used methods for determining the AVP, a set of optimal computation procedures for the STM is also suggested. In addition, aimed at drawbacks of the intercept method, an improved approach with a new computation procedure is also presented to plot the celestial line of position without the intercept. The improved approach with iteration scheme is used to solve the AVP and validate the SEEM successfully. Methods of solving AVP problems are also discussed in detail. Finally, a benchmark example is included to demonstrate these proposed methods.

Use of a sphere to represent the Earth in the teaching of navigation has the advantage that the mathematics is relatively simple and has sufficient accuracy for most practical purposes. It also allows relatively simple instructional material to be developed for plane and Mercator sailing. Unfortunately, and as remarked by Williams [1], bad practice based on an error of principle has pervaded some navigation texts for some time. This error has passed into various instructional settings where it has gone un-noticed or un-remarked. The error lies in the un-rigorous use of meridional parts for the spheroidal earth together with latitude differences for the spherical earth in the teaching of plane and Mercator sailing. This is exemplified in [2, example1, p 585]. It is often argued that the resulting error in calculated distance or mid-latitude caused by this un-rigorous treatment is small and within what practical course keeping allows. However, permitting the discrepancy to remain unexplained is a disservice to students of navigation. Students should be given a clear explanation of the differences between the fictitious though useful spherical model of the earth and the spheroidal earth as presently described by WGS84. Teaching of plane and Mercator sailings should be based upon either the spherical model or upon the spheroidal model but not on parts taken from both.