Geomagnetic Information Research Articles

Effect of geomagnetic field on migratory activity in a diurnal passerine migrant, the dunnock, Prunella modularis

Migratory songbirds are guided by an endogenous programme during their first migration, encoding timing of migration, distance and direction. To successfully perform migration, birds have evolved phenotypic adaptations for flight, fuelling and navigation. Migratory distance in different species of birds is encoded as a period of expressed migratory restlessness, for which the length is correlated with migratory distance. Most of the work so far has been on nocturnal passerine migrants, while much less is known about the phenotypic adaptations for migration in diurnal migrants. Here we studied autumn migration fuelling and expression of migratory activity in caged diurnally migrating juvenile dunnocks in response to magnetic displacements. We kept one group (control) indoors at the location of capture in south Sweden, while the two experimental groups were gradually (over 5 days) displaced magnetically to locations to the northeast or to the wintering destination in southwest France. We found that all birds showed two peaks of activity during the day, for which the onset of activity was tightly timed to sunrise and sunset. The longest activity (2–3 h) occurred in the morning, coinciding with the natural period of migration for this species. For the control group, the migratory (flight) activity increased with the season (15 days), while it was strongly reduced for the dunnocks displaced to the wintering areas. Birds displaced to the north showed a stable, but slightly reduced migratory activity over time. The results support the finding that geomagnetic information expected to be met en route is important for triggering level of migratory activity in juveniles of a diurnal songbird migrant.

Ten grams and 13,000\xa0km on the wing \u2013 route choice in willow warblers Phylloscopus trochilus yakutensis migrating from Far East Russia to East Africa

BackgroundHigh-latitude bird migration has evolved after the last glaciation, in less than 10,000–15,000 years. Migrating songbirds rely on an endogenous migratory program, encoding timing, fueling, and routes, but it is still unknown which compass mechanism they use on migration. We used geolocators to track the migration of willow warblers (Phylloscopus trochilus yakutensis) from their eastern part of the range in Russia to wintering areas in sub-Saharan Africa. Our aim was to investigate if the autumn migration route can be explained by a simple compass mechanism, based on celestial or geomagnetic information, or whether migration is undertaken as a sequence of differential migratory paths possibly involving a map sense. We compared the recorded migratory routes for our tracked birds with simulated routes obtained from different compass mechanisms.ResultsThe three tracked males were very similar in the routes they took to their final wintering sites in southern Tanzania or northern Mozambique, in their use of stopover sites and in the overall timing of migration. None of the tested compass mechanisms could explain the birds’ routes to the first stopover area in southwest Asia or to the destination in Southeast Africa without modifications. Our compass mechanism simulations suggest that the simplest scenarios congruent with the observed routes are based on either an inclination or a sun compass, assuming two sequential steps.ConclusionsThe birds may follow a magnetoclinic route coinciding closely with the tracks by first moving west, i.e. closer to the goal, and thereafter follow a constant apparent angle of inclination to the stopover site. An alternative would be to use the sun compass, but with time-adjustments along the initial part of the migration to the first stopover, and thereafter depart along a new course to the winter destination. A combination of the two mechanisms cannot be ruled out, but needs to be confirmed in future studies.

Magnetic map in nonanadromous Atlantic salmon

Long-distance migrants, including Pacific salmon (Oncorhynchus spp), can use geomagnetic information to navigate. We tested the hypothesis that a "magnetic map" (i.e., an ability to extract positional information from Earth's magnetic field) also exists in a population of salmon that do not undertake oceanic migrations. This study examined juvenile Atlantic salmon (Salmo salar) originally from a nonanadromous population in Maine transferred ∼60 years ago to a lake in central Oregon. We exposed juveniles to magnetic displacements representative of locations at the latitudinal boundaries of the Pacific salmon oceanic range in the North Pacific and at the periphery of their ancestral oceanic range in the North Atlantic. Orientation differed among the magnetic treatments, indicating that Atlantic salmon detect map information from the geomagnetic field. Despite no recent history of ocean migration, these fish displayed adaptive orientation responses similar to those observed in native Pacific salmonids. These findings indicate that use of map information from the geomagnetic field is a shared ancestral character in the family Salmonidae and is not restricted to populations with anadromous life histories. Lastly, given that Atlantic salmon are transported throughout the world for capture fisheries and aquaculture, such a robust navigational system is of some concern. Escaped individuals may have greater potential to successfully navigate, and thus invade, introduced habitats than previously suspected.

The threat of global mercury pollution to bird migration: potential mechanisms and current evidence.

Mercury is a global pollutant that has been widely shown to adversely affect reproduction and other endpoints related to fitness and health in birds, but almost nothing is known about its effects on migration relative to other life cycle processes. Here I consider the physiological and histological effects that mercury is known to have on non-migrating birds and non-avian vertebrates to identify potential mechanisms by which mercury might hinder migration performance. I posit that the broad ability of mercury to inactivate enzymes and compromise the function of other proteins is a single mechanism by which mercury has strong potential to disrupt many of the physiological processes that make long-distance migration possible. In just this way alone, there is reason to expect mercury to interfere with navigation, flight endurance, oxidative balance, and stopover refueling. Navigation and flight could be further affected by neurotoxic effects of mercury on the brain regions that process geomagnetic information from the visual system and control biomechanics, respectively. Interference with photochemical reactions in the retina and decreases in scotopic vision sensitivity caused by mercury also have the potential to disrupt visual-based magnetic navigation. Finally, migration performance and possibly survival might be limited by the immunosuppressive effects of mercury on birds at a time when exposure to novel pathogens and parasites is great. I conclude that mercury pollution is likely to be further challenging what is already often the most difficult and perilous phase of a migratory bird's annual cycle, potentially contributing to global declines in migratory bird populations.

Geomagnetic Gradient Bionic Navigation Based on Parallel Approach Method

Priori geomagnetic information is important to the geomagnetic navigation. However in practice, the precision of the geomagnetic information is a greatly constraint to the development of the geomagnetic navigation. In order to solve this problem, this paper present a geomagnetic gradient bionic navigation method based on parallel approach without any priori information. Inspired by the evidence that many creatures can navigate using the Earth magnetic field, the navigation process can be considered as a convergence of multi-objective problem, and develop the bionics navigation model. By introducing the parallel approach method to the navigation process, the heading angle can be estimated with the information of magnetic field gradient. The simulation results show the proposed method is able to navigation effectively without magnetic priori information, just rely on the actual geomagnetic measurement, which has implies potential application in the future.

Indoor Pedestrian Tracking Using Consumer-Grade Inertial Sensors With PZTD Heading Correction

Foot-mounted navigation based on inertial navigation sensors struggles with unobservable heading error. Existing solutions for heading error rely on acquiring geomagnetic information or prior knowledge, such as building maps, which are susceptible to magnetic disturbance or lack of maps, respectively. A prominent approach to mitigate the heading error is by applying heuristic drift elimination (HDE), where orthogonal indoor corridors are used as reference for headings. Any heading discrepancy in walking straight along the orthogonal corridors or so-called dominant directions will be attenuated. State of the art emphasizes that HDE should not correct the heading when pedestrians walk along curved paths or straight paths in non-dominant directions; if it is not a case, over-correction will occur and lead to wrong trajectories. Also, the techniques to determine the type of walks heavily rely on thresholding, which is dependent on the person or operating conditions. In this paper, a threshold-less turn detection method known as pelvic rotation-ZUPT turn detector has been applied to correct the heading in the Kalman filter-based foot-mounted navigation. The turning information proves to be a significant aid to the pedestrian tracking even though consumer-grade inertial sensors are used. The pedestrian tracking system achieves return position error and traveled distance error about 2.3% and 2.9% in average, respectively.

A Foot-Mounted Inertial Measurement Unit (IMU) Positioning Algorithm Based on Magnetic Constraint.

With the development of related applications, indoor positioning techniques have been more and more widely developed. Based on Wi-Fi, Bluetooth low energy (BLE) and geomagnetism, indoor positioning techniques often rely on the physical location of fingerprint information. The focus and difficulty of establishing the fingerprint database are in obtaining a relatively accurate physical location with as little given information as possible. This paper presents a foot-mounted inertial measurement unit (IMU) positioning algorithm under the loop closure constraint based on magnetic information. It can provide relatively reliable position information without maps and geomagnetic information and provides a relatively accurate coordinate for the collection of a fingerprint database. In the experiment, the features extracted by the multi-level Fourier transform method proposed in this paper are validated and the validity of loop closure matching is tested with a RANSAC-based method. Moreover, the loop closure detection results show that the cumulative error of the trajectory processed by the graph optimization algorithm is significantly suppressed, presenting a good accuracy. The average error of the trajectory under loop closure constraint is controlled below 2.15 m.

Geomagnetic matching navigation algorithm based on robust estimation

The outliers in the geomagnetic survey data seriously affect the precision of the geomagnetic matching navigation and badly disrupt its reliability. A novel algorithm which can eliminate the outliers influence is investigated in this paper. First, the weight function is designed and its principle of the robust estimation is introduced. By combining the relation equation between the matching trajectory and the reference trajectory with the Taylor series expansion for geomagnetic information, a mathematical expression of the longitude, latitude and heading errors is acquired. The robust target function is obtained by the weight function and the mathematical expression. Then the geomagnetic matching problem is converted to the solutions of nonlinear equations. Finally, Newton iteration is applied to implement the novel algorithm. Simulation results show that the matching error of the novel algorithm is decreased to 7.75% compared to the conventional mean square difference (MSD) algorithm, and is decreased to 18.39% to the conventional iterative contour matching algorithm when the outlier is 40nT. Meanwhile, the position error of the novel algorithm is 0.017° while the other two algorithms fail to match when the outlier is 400nT.

The magnetic map sense and its use in fine-tuning the migration programme of birds.

The Earth's magnetic field is one of several natural cues, which migratory birds can use to derive directional ("compass") information for orientation on their biannual migratory journeys. Moreover, magnetic field effects on prominent aspects of the migratory programme of birds, such as migratory restlessness behaviour, fuel deposition and directional orientation, implicate that geomagnetic information can also be used to derive positional ("map") information. While the magnetic "compass" in migratory birds is likely to be based on radical pair-forming molecules embedded in their visual system, the sensory correlates underlying a magnetic "map" sense currently remain elusive. Behavioural, physiological and neurobiological findings indicate that the sensor is most likely innervated by the ophthalmic branch of the trigeminal nerve and based on magnetic iron particles. Information from this unknown sensor is neither necessary nor sufficient for a functional magnetic compass, but instead could contribute important components of a multifactorial "map" for global positioning. Positional information could allow migratory birds to make vitally important dynamic adaptations of their migratory programme at any relevant point during their journeys.

Geomagnetic information modulates nocturnal migratory restlessness but not fueling in a long distance migratory songbird

Geomagnetic cues have been shown to influence migratory orientation and migratory fuelling in night‐migratory songbird species. Here, we used captive‐bred northern wheatears Oenanthe oenanthe from the southern Norwegian population to show that other aspects of the birds’ migratory program can be influenced by magnetic cues as well. We observed that the amount of migratory restlessness increased strongly with progression of the migratory season when the birds were kept constantly in the magnetic field of northern Germany, but the amount of migratory restlessness decreased when the magnetic field changed along the birds’ natural flyway are simulated. Thus, the Earth's magnetic field can also act as a ‘signpost’ cue for fine‐tuning the spatio‐temporal course of migration.

Basmag: An Optimized HMM-Based Localization System Using Backward Sequences Matching Algorithm Exploiting Geomagnetic Information

Due to the complex building construction materials, the geomagnetic field has great anomalies in indoor environments. These anomalies generate distinctive signatures corresponding to positions. Many hybrid localization schemes that combine geomagnetic information and pedestrian dead reckoning (PDR) have been proposed. In this paper, we regard these distinctive geomagnetic anomalies as fingerprints for high precision indoor positioning. In order to improve the hybrid localization accuracy, we present Basmag, a robust hidden Markov model (HMM)-based indoor localization system, and we also propose a backward sequences matching algorithm (BSMA) to optimize the HMM. In order to improve the low discernibility of single geomagnetic signal, we vectorize the backward consecutive geomagnetic signals to fingerprint sequences with the help of PDR. We match the backward sequences with a pre-constructed fingerprint database to get more precise transition probabilities in HMM. We conducted a theoretical analysis of the feasibility of the BSMA. Extensive simulation results show that Basmag can achieve high-accuracy positioning. Finally, we conducted experiments performed on a smartphone in an indoor area to compare Basmag with other geomagnetic field-based and WiFi-based localization methods, and the experimental results verify the effectiveness and robustness among users with different walking styles of Basmag.

Assessing vector navigation in long-distance migrating birds

Birds migrating between distant locations regularly perform long continuous flights lasting several days. What compass mechanism they use is still a mystery. Here, we use a novel approach, applying an individual-based model, taking compass mechanisms based on celestial and geomagnetic information and wind into account simultaneously, to investigate what compass mechanism likely is used during long continuous flights and how wind drift or compensation affects the resulting tracks. We found that for the 6 cases of long continuous migration flights, the magnetoclinic route could best explain the route selection in all except one case compared with the alternative compass mechanisms. A flight strategy correcting for wind drift resulted most often in routes ending up closest to the predicted destinations. In only half of the cases could a time-compensated sun compass explain the migration routes observed with sufficient precision. Migration from Europe to the Siberian tundra was especially challenging to explain by one compass mechanism alone, suggesting a more complex navigation strategy. Our results speak in favor of a magnetic compass based on the angle of inclination used by birds during continuous long-distance migration flights, but also a capacity to detect and correct for drift caused by winds along the route.

Visual Cortical Prosthesis with a Geomagnetic Compass Restores Spatial Navigation in Blind Rats

Allocentric sense is one of the major components that underlie spatial navigation [1, 2]. In blind patients, the difficulty in spatial exploration attributes at least partly to the deficit of absolute direction perception [3, 4]. In support of this notion, we announce that blind adult rats can perform spatial tasks normally when externally provided with a real-time feedback of their head directions. Head-mountable microstimulators coupled with a digital geomagnetic compass were bilaterally implanted in the primary visual cortex of adult rats whose eyelids had been sutured. These "blind" rats were trained to seek food pellets in a T-shaped maze or a more complicated maze. Within tens of trials, they learned to manage the geomagnetic information source to solve the mazes. Their performance levels and navigation strategies were similar to those of normally sighted, intact rats. Thus, blind rats can recognize self-location through extrinsically provided stereotactic cues.

New cue-conflict experiments suggest a leading role of visual cues in the migratory orientation of Pied Flycatchers Ficedula hypoleuca

Migratory birds use both geomagnetic and celestial cues to select and maintain their seasonally appropriate migratory direction. The integration of the different compass cues is still poorly understood. Previous cue-conflict experiments suggested that Pied Flycatchers Ficedula hypoleuca did not recalibrate their magnetic compass against the polarization pattern at twilight, but the available evidence is problematic given the high variability of birds’ directional preferences. We performed a new set of cue-conflict experiments where (1) we modified the protocol in order to try to reduce scatter of data and (2) we integrated the results of two experimental approaches, i.e. orientation cages and releases of radio-tagged birds. Pied Flycatchers were tested in Emlen funnels without access to celestial cues before and after being exposed to conflicting visual and geomagnetic information. After the second test, birds were equipped with radio-transmitters and followed until the vanishing of the radio signal. Contrary to previous experiments, our data showed a general dominance of celestial cues: polarized light sun-related pattern in captive birds tested without access to stars and stellar dominance in free-flying birds released under a starry sky at night-time. These results underline the importance of experimental protocols when testing ways in which birds integrate their compass systems.

Long-Distance Geomagnetic Navigation: Imitations of Animal Migration Based on a New Assumption

Plenty of evidence has implied that animals like pigeons and sea turtles utilize geomagnetic information for long-distance migration and homing. In this paper, we conduct an ab initio investigation to imitate a migratory animal's geomagnetic homing across a long distance over the surface of the Earth. Based on a simple assumption that such animals have a natural ability to sense and compare the included angle between the vector geomagnetic field (GF) and a specific geographic direction such as the due north, we show that a long-distance geomagnetic navigation (GN) can be accomplished without any assistance of prestored geomagnetic and geographic information, as long as the navigation is inside a vast area where such a spatial angle can uniquely determine a geographic location. Without any requirement of measuring the strength of the GF, this GN will not be visibly affected by the recurrent fluctuation of the GF that severely hampers traditional GN. By introducing the extended-Kalman-filter algorithm, it is able to find a shortcut in the geomagnetic space, overcoming interferences of strong Gaussian and local-area geomagnetic anomaly. We believe that the proposed approach will find a wide range of potential applications in global, local, and indoor navigations based on magnetic field in the future.

Cryptochrome-dependent magnetic field effect on seizure response in Drosophila larvae.

The mechanisms that facilitate animal magnetoreception have both fascinated and confounded scientists for decades, and its precise biophysical origin remains unclear. Among the proposed primary magnetic sensors is the flavoprotein, cryptochrome, which is thought to provide geomagnetic information via a quantum effect in a light-initiated radical pair reaction. Despite recent advances in the radical pair model of magnetoreception from theoretical, molecular and animal behaviour studies, very little is known of a possible signal transduction mechanism. We report a substantial effect of magnetic field exposure on seizure response in Drosophila larvae. The effect is dependent on cryptochrome, the presence and wavelength of light and is blocked by prior ingestion of typical antiepileptic drugs. These data are consistent with a magnetically-sensitive, photochemical radical pair reaction in cryptochrome that alters levels of neuronal excitation, and represent a vital step forward in our understanding of the signal transduction mechanism involved in animal magnetoreception.

Variable remanence acquisition efficiency in sediments containing biogenic and detrital magnetites: Implications for relative paleointensity signal recording

AbstractWidespread geological preservation of biogenic magnetite makes it important to assess how such particles contribute to sedimentary paleomagnetic signals. We studied a sediment core from the South China Sea that passes the strict empirical criteria for magnetic “uniformity” used in relative paleointensity studies. Such assessments are based routinely on bulk magnetic parameters that often fail to enable identification of mixed magnetic mineral assemblages. Using techniques that enable component‐specific magnetic mineral identification, we find that biogenic and detrital magnetites occur in approximately equal concentrations within the studied sediments. We analyzed normalized remanence signals associated with the two magnetite components to assess whether co‐occurring biogenic and detrital magnetites record geomagnetic information in the same way and with the same efficiency. Paleomagnetic directions for the two components have no phase lag, which suggests that the biogenic and detrital magnetites acquired their magnetizations at equivalent times. However, we find that the biogenic magnetite is generally 2–4 times more efficient as the detrital magnetite in contributing to the natural remanent magnetization (NRM) despite their approximately equal magnetic contributions. Variations in the concentration and efficiency of remanence acquisition of the two components suggest that a significant part of the NRM is controlled by nongeomagnetic factors that will affect relative paleointensity recording. We recommend that methods suited to the detection of variable recording efficiency associated with biogenic and detrital magnetites should be used on a routine basis in relative paleointensity studies.

The Method of dealing with Geomagnetic Anomaly caused by Movable Magnetic Objects in Drawing the Geomagnetic Chart

The local geomagnetic chart is an effective tool to describe the geomagnetic information in the region accurately and visually which is a reference in application for future. Precision of local geomagnetic chart directly affects its value. When the movable magnetic objects are in the region, the distribution of geomagnetic field will be changed. When the movable magnetic objects are out the region, the distribution of geomagnetic field will recover to normal situation. Thus, magnetic objects can bring the error to some measured data. As an result, precision of the geomagnetic chart will reduce. On the basis of analysis of the existing geomagnetic model, the method to eliminate the movable geomagnetic anomaly in drawing the chart is proposed which is based on Taylor polynomial model. In this method, affected regions by magnetic object are gotten, the geomagnetic model are built in these affected region by precise data, the measured data in these region is replayed with model data, finally, the geomagnetic chart is draw by combined data using Kriging interpolation algorithm. The experiment results show that the method can improve the precision of the local magnetic chart when the movable magnetic objects exist in the measurement region.

Nonlinear filtering techniques for geomagnetic navigation

This article focuses on the application of different nonlinear filtering techniques for geomagnetic navigation, including extended Kalman filter, unscented Kalman filter, particle filter and extended Kalman particle filter. The research evaluates the four methods for navigation of missile during its cruise phase. The measurement equations are obtained by using a surface spline method with the real regional geomagnetic data. Simulation results show all the filters have good performance in areas with abundant geomagnetic information. Among the four filters, unscented Kalman filter tops in the convergence rate and precision with a fairly low tuning sensitivity to the flight path. As the performance of unscented Kalman filter effect is influenced by unscented conversion parameters, a method of parameters optimization using genetic algorithm is presented. The method’s feasibility is further demonstrated by robustness analysis of optimal parameters.

An Autonomous Navigation Algorithm Using Geomagnetic Sensor and Star Sensor

Aiming at the limitations of the orbital dynamic equations based star sensor navigation method, a star sensor /geomagnetic information utilized aircraft autonomous navigation method is proposed. Dynamic equations applicable to general aircrafts are established. System observation equations are deduced. The angle between geomagnetic and starlight vector is used as observation in the algorithm. Extended Kalman filter is used to estimate position and velocity of aircraft in the algorithm. Singular value decomposition method is used to analyze observability of the system. Simulation results show that the algorithm has many advantages including high precision, good filtering convergence and stability, and non-accumulated error. The algorithm can be used as aided navigation of inertial navigation or in occasions, which only require a general navigation precision.