The History of Air Navigation Group commissioned the author to provide a brief account of airborne DR development by discussing both the methods and the equipment used in the air. This first part covers the period before 1940. The split is arbitrary, although it is obvious from a British perspective that military events around that date had a major impact on the pace of navigation development. However, it is equally obvious that airborne DR developed alongside a worldwide technical and intellectual revolution. This aspect of the story is abstract and involves some conjecture, so the paper takes it for granted and concentrates instead on practical matters. Accounts of air navigators' experiences as well as material on DR theory and descriptions of DR equipment in navigation manuals, journals and various surviving research documents have been used as the source material.

Three textual works by Olaus Magnus (1490–1557) hold the key to the ‘compass’ on his invented island of Hvitsark, shown on his 1539 Carta marina. Although Olaus had little general understanding of the magnetic compass or of navigation in the Far North, he evidently did not intend the navigational device he drew on Hvitsark to represent a magnetic compass, but a sundial. His muddled ideas about the relationship between 12 wind-directions and direction-finding at sea by means of such a dial appear related to his second-hand information about a gnomonic navigational device used by the medieval Norse.

Birds can accurately navigate over hundreds to thousands of kilometres, and use celestial and magnetic compass senses to orient their flight. How birds determine their location in order to select the correct homeward bearing (map sense) remains controversial, and has been attributed to their olfactory or magnetic senses. Pigeons can hear infrasound down to 0·05 Hz, and an acoustic avian map is proposed consisting of infrasonic cues radiated from steep-sided topographic features. The source of these infrasonic signals is microseisms continuously generated by interfering oceanic waves. Atmospheric processes affecting the infrasonic map cues can explain perplexing experimental results from pigeon releases. Moreover, four recent disrupted pigeon races in Europe and the north-eastern USA intersected infrasonic shock waves from the Concorde supersonic transport. Having an acoustic map might also allow clock-shifted birds to test their homeward progress and select between their magnetic and solar compasses.

The drift of sea ice ridges and hits on an offshore structure with dimensions 200 m by 200 m have been studied for the Dolginskoye oil field in the Pechora Sea. The calculations were made with the computer program ICEBERG. The mean drift speed of the ice ridges was found to be 0·21 m/s with a maximum speed of 0·89 m/s. The expected number of hits per year was calculated to be 737. It was assumed that a total number of 133000 sea ice ridges would be produced in (or have entered) the Pechora Sea per year. Under the same assumption, the expected number of ridges entering a safety zone around a platform of 1852 m by 1852 m was found to be 5649. However, due to uncertainties concerning the population of ridges, their shapes, sizes, drag coefficients and tidal action, the results should be used with care and only considered as indicative. The ridge drift pattern was predominantly to the northeast in the winter months. A structure located at Dolginskoye will most probably be exposed to sea ice ridges that are formed in the area around Khodovarihka.

This paper presents the preliminary study of a stratospheric segment within a satellite navigation system of present and future generation (GPS and Galileo) implemented by means of High Altitude and Very long Endurance (HAVE) platforms. The paper discusses a possible scenario in which the main features of the HAVE platform are exploited to define an innovative Aerial-Based Augmentation System (ABAS) for the provision of differential services. This particular local segment improves the provision of a differential navigation service. It is suited to the broadcasting of differential corrections in critical areas such as mountainous and sea regions where, to guarantee wide coverage, a large number of terrestrial reference stations would otherwise be required. The study includes a description of the proposed DGPS augmentation system, and a discussion of the system architecture and expected performance.

This paper presents a concept on the subjective ship domain. The factors related to the domain are discussed. A method based on the neural networks is used to establish a model of the domain that considers the effects of visibility and manoeuvrability, which can react quickly to various ships within a certain range.

Predicted flight trajectories differ depending on which orientation cues are used by migrating birds. Results from radar and satellite tracking of migrating birds can be used to test which of the predicted trajectories shows the best fit with observed flight routes, supporting the use of the associated orientation mechanism. Radar studies of bird migration at the Northeast Passage and the Northwest Passage support the occurrence of migration along sun compass routes in these polar regions. In contrast, satellite tracking of Brent geese (Branta bernicla) migrating from Iceland across Greenland and from Northwest Europe to Siberia show routes that conform most closely with geographic loxodromes, but which are also profoundly influenced by large-scale topography. These evaluations are discussed in relation to the adaptive values of different routes in different parts of the world. Sun compass routes are favourable mainly for east-west migration at high latitudes. For east-west migration at mid and high latitudes magnetic loxodromes are more favourable than geographic loxodromes in certain regions while the reverse holds in other regions. The geometry of migration routes, as recorded by radar and satellite tracking, may be important for understanding the evolution of the complexity of birds' orientation systems, and for providing clues about the orientation mechanisms guiding the birds on their global journeys.

Migrating pierid butterflies use a sun compass in order to head in a preferred flight direction. When blown off-course by the wind, butterflies adjust their heading to compensate for cross-track wind drift. They are capable of drift compensation over water when and where landmarks are visible on the shore. They are also capable of a more inaccurate form of drift compensation over the sea when and where landmarks are not visible.

An integrated GPS/INS navigation system can employ inertial velocity information to produce a more robust system. For a stand-alone GPS receiver, decreasing the receiver tracking loop bandwidth reduces the probability of losing lock in a jamming or interference environment if vehicle dynamics are low. However, reduced bandwidth increases tracking errors when dynamics are present. Beyond a certain limit, it causes a serious degradation in the dynamic tracking loop performance. Providing inertial velocity aiding to the receiver tracking loops is an effective and popular treatment to help resolve this problem. In this paper, performance of the GPS receiver tracking loops using inertial velocity aiding will be investigated. Different types of tracking loops, from 1st to 3rd order, are covered. Following the discussion of the system architecture and derivation of the related transfer functions for the tracking loops, both with and without aiding, the system performance, including transient response, steady-state error, and noise bandwidth is evaluated.

Geometric Dilution Of Precision (GDOP) is a factor that describes the effect of geometry on the relationship between measurement error and position determination error. It is used to provide an indication of the quality of the solution. Conventional closed-form GDOP calculation formula applied to all possible combinations of visible satellites is rather time consuming, especially as the number of satellites grows. Approximations, such as the maximum volume method, are faster but optimum selection is not guaranteed. In this paper, a more concise but efficient solution for the calculation of GDOP value in the case of four Global Positioning System (GPS) satellites is firstly reviewed and then extended to cover the other forms of dilution of precision (DOP) values, including vertical DOP (VDOP) and horizontal DOP (HDOP). Secondly, a review and extension of the conventional solution is performed in the case of three GPS satellites aided by an altimeter. Based on the ideas gained from these two approaches, a simpler closed-form DOP formula for three GPS satellites aided by an altimeter is derived. The advantage of the proposed formulation is that it is simpler and thus reduces the computational load in comparison to the conventional one.

Albatrosses and sea turtles are known to perform extremely long-distance journeys between disparate feeding areas and breeding sites located on small, isolated, oceanic islands or at specific coastal sites. These oceanic journeys, performed mainly over or through apparently featureless mediums, indicate impressive navigational abilities, and the sensory mechanisms used are still largely unknown. This research used three different approaches to investigate whether bi-coordinate navigation based on magnetic field gradients is likely to explain the navigational performance of wandering albatrosses in the South Atlantic and Indian Oceans and of green turtles breeding on Ascension Island in the South Atlantic Ocean. The possibility that magnetic field parameters can potentially be used in a bi-coordinate magnetic map by wandering albatrosses in their foraging area was investigated by analysing satellite telemetry data published in the literature. The possibilities for using bi-coordinate magnetic navigation varied widely between different areas of the Southern Oceans, indicating that a common mechanism, based on a bi-coordinate geomagnetic map alone, was unlikely for navigation in these areas. In the second approach, satellite telemetry was used to investigate whether Ascension Island green turtles use magnetic information for navigation during migration from their breeding island to foraging areas in Brazilian coastal waters. Disturbing magnets were applied to the heads and carapaces of the turtles, but these appeared to have little effect on their ability to navigate. The only possible effect observed was that some of the turtles with magnets attached were heading for foraging areas slightly south of the control turtles along the Brazilian coast. In the third approach, breeding female green turtles were deliberately displaced in the waters around Ascension Island to investigate which cues these turtles might use to locate and return to the island; the results suggested that cues transported by wind might be involved in the final stages of navigation.

The high cost of inertial units is the main obstacle for their inclusion in precision navigation systems to support a variety of application areas. Standard inertial navigation systems (INS) use precise gyro and accelerometer sensors; however, newer inertial devices with compact, lower precision sensors have become available in recent years. This group of instruments, called motion sensors, is six to eight times less costly than a standard INS. Given their weak stand-alone accuracy and poor run-to-run stability, such devices are not usable as sole navigation systems. Even the integration of a motion sensor into a navigation system as a supporting device requires the development of non-traditional approaches and algorithms. The objective of this paper is to assess the feasibility of using a motion sensor, specifically the MotionPak™, integrated with DGPS and DGLONASS information, to provide accurate position and attitude information, and to assess its capability to bridge satellite outages for up to 20 seconds. The motion sensor has three orthogonally mounted ‘solid-state’ micro- machined quartz angular rate sensors, and three high performance linear servo accelerometers mounted in a compact, rugged package. Advanced algorithms are used to integrate the GPS and motion sensor data. These include INS error damping, calculated platform corrections using DGPS (or DGPS/DGLONASS) output, velocity correction, attitude correction and error model estimation for prediction. This multi-loop algorithm structure is very robust, which guarantees a high level of software reliability. Vehicular and aircraft test trials were conducted with the system in land vehicle mode and the results are discussed. Simulated outages in GPS availability were made to assess the bridging accuracy of the system. Results show that a bridging accuracy of up to 3 m after 10 seconds in vehicular mode and a corresponding accuracy of 6 m after 20 seconds in aircraft mode can be obtained, depending on vehicle dynamics and the specific MotionPak™ unit used. The attitude accuracy was on the order of 22 to 25 arcmin for roll and pitch, and about 44 arcmin for heading.

In the near future, Spaced-Based Augmentation Systems (such as the Wide Area Augmentation System in North America) will become operational, permitting the use of GPS as a primary system for all phases of flight. Recently the International Civil Aviation Organisation (ICAO) has recommended the use of un-augmented GPS as a supplemental navigation system for all phases of flight including non-precision approaches. In this paper, the salient features of the Air Traffic Control (ATC) system in India, and the use of conventional navigational aids are described. A new landing procedure is proposed using un-augmented GPS known as ‘a non-precision instrument approach procedure with vertical guidance (IPV)’ for Hyderabad Airport, Runway 27. This procedure, if implemented, would be cost-effective and reliable for many airports in India. An algorithm has also been developed for determining the range and bearing between the departure and the arrival waypoints of an aircraft using the IPV.

Any vehicle such as a vessel or aeroplane has three attitude parameters. These are most commonly defined as pitch, roll and heading from true north. In hydrographic surveying, determination of these parameters is essential for the correction of multi-beam echo sounder measurements. In the study on which this paper is based, two of the three parameters, the pitch and roll angles, were measured with an inexpensive IMU (Inertial Measurement Unit) device. The third was calculated from GPS carrier phase measurements that were collected from two antennas on the boat. The GPS antennas depart from the vertical when they are subject to pitch and roll effects. In this case, the coordinates derived from GPS will be erroneous. Thus, if heading is to be calculated accurately, the horizontal coordinates have to be corrected for pitch and roll. This paper defines an algorithm for the purpose that enables pitch and roll angles to be measured with an accuracy of about 0·003 arcdeg and headings computed with an accuracy of about 0·010 arcdeg.

Animals use many different mechanisms to navigate in space. The characteristics of the mechanism employed are usually well-suited to the demands of each particular navigational problem. For example, desert ants navigating in a relatively featureless environment use path integration, birds homing or migrating over long distances use compasses of various sorts, salmon returning to their natal stream home on olfactory cues. The study of navigation requires the study of many different taxa confronting different problems. One interesting case involves scatter-hoarding species that use memory to relocate their hidden food. Such animals face the problem of remembering many locations simultaneously. Clark's nutcrackers (Nucifraga columbiana) are an excellent example, and this paper considers their possible use of multiple bearings from landmarks.

Although GPS positioning errors are now well described, there are still some uncertainties regarding the impact of some rare space weather phenomena on GPS positioning accuracy. Solar eclipses have been considered as one source of such rare events, so the 1999 solar eclipse gave the opportunity to collect horizontal GPS positioning data for further analysis. The results of statistical analysis show no deterioration of horizontal GPS positioning accuracy. Space weather, ionospheric and geomagnetic conditions were also carefully analysed and showed no significant activity. In conclusion, the experiment confirmed negligible impact of the 1999 solar eclipse on horizontal GPS positioning accuracy, and opens discussion concerning application of satellite positioning systems in space and ionospheric weather monitoring.

This paper discusses the knowledge and culture of astronomy possessed by the Maya civilisation and how this might have been used for marine navigation in the 8th Century. Comparison is made with the European view and use of celestial positioning.

The International Maritime Organisation (IMO), in its Sub-Committee for the Safety of Navigation, has recommended the acceptance of GPS as a component of the World-Wide Radionavigation System. However, the Sub-Committee highlighted that GPS accuracy is not sufficient for harbour entrances and approaches and that it does not provide instantaneous integrity to alert users of any malfunction. The Sub-Committee considered that DGPS could improve both the accuracy and the integrity of GPS. In practice, the use of differential corrections to GPS signals allows elimination of most of the errors of GPS and improves the integrity of the service significantly. While GPS does not provide instantaneous integrity, the use of DGPS reference stations, which continuously monitor the signals of the visible satellites, enables the timely warning (under 15 seconds) of any malfunction or failure. However, the recent discontinuation of Selective Availability (SA), which led to an improvement in stand-alone GPS accuracy, has changed some of the premises that justified differential services. This paper presents the needs of mariners in terms of radio positioning, with the aim of evaluating the ability of unaugmented GPS and DGPS to comply with marine navigation requirements. The impact of the removal of SA on DGPS and its benefits for mariners will also be discussed in order to show that DGPS is still adequate and useful for mariners.

An integrated multi-sensor vehicle navigation system is presented that uses a low-cost rate gyro and differential odometry to supplement GPS under signal masking conditions such as tree foliage and urban canyons. Signal masking is often accompanied by extreme multi-path in urban centres with tall buildings, and is also found in wooded areas, enclosed car parks, tunnels, etc. The purpose of the system tested is to provide an accuracy of better than 20 metres almost 100% of the time throughout these interruptions, which are assumed to last up to a few minutes. The equipment used is discussed in detail, as is the method used for filtering measurements. Results are presented from tests carried out in an urban core with relatively long periods of signal loss – up to several minutes over a 6-km test circuit. Tests in urban canyons demonstrate that it is difficult to reach the above specifications with aiding from differential odometry alone due to the high precision of the wheel-scale factor required. However, with the use of a rate gyro and odometry, RMS errors are below 20 metres while availability is nearly 100%. Some of the large deviations could probably be better controlled if GPS multi-path errors were detected before they are allowed to corrupt the filtered solution.