Predictions of bird swing from GPS coordinates

Bird attitudes, with roll, pitch, and yaw angles, are required for modeling the measured electromagnetic response of the earth. Global Positioning System (GPS) antennas can be used in airborne electromagnetic (AEM) systems to monitor airborne platform attitude and bird maneuver. We have found evidence from photographic sequences that four GPS antennas, three on the bird and one on the aircraft, generally are adequate for angular and altitude geometry control. The mounting system for the bird frame introduces vibration noise. We have developed a model that predicts bird maneuver from the use of GPS antennas already present during routine airborne surveys. The bird motion, whether inline or crossline, is modeled from the difference between the aircraft location and the mean location of the bird. This also accurately predicts the roll of the bird when an inline yoke mounting is used. The minimum number of GPS antennas required to monitor the motion of a cylindrical electromagnetic (EM) bird typical of frequency-domain systems is two, one on the aircraft and one on the bird. We have defined optimum locations of GPS antennas to enable geometric monitoring of towed-bird systems. The findings suggest that the bird be mounted with two aerodynamically efficient GPS antennas, one on the nose and one on the tail. This enables the measurement of the pitch and yaw of the bird, with roll deduced using the third GPS on the helicopter.

This study investigated long-term land subsidence derived from borehole extensometer and Global Positioning System (GPS) observations from Addicks, a suburb located in West Houston, Texas. The Addicks borehole extensometer was built in 1974 by the USGS. Two GPS stations were installed at this site in 1993 and 1996, respectively. One GPS antenna (ADKS) is mounted on the inner pipe of the extensometer borehole, which is firmly anchored 549 m below the land surface. Another GPS antenna (PA05) is mounted on a permanent antenna pole anchored 6 m below the land surface. The horizontal distance between these two GPS antennas is 50 m. Continuous GPS data collected from the deeply anchored GPS antenna indicate that the bottom of the borehole has been stable over the past 20 years (1993–2012). Hence the compaction derived from the borehole extensometer data represents the total subsidence at this site, which should be approximately equivalent to the vertical displacement (subsidence) recorded by the shallowly anchored GPS antenna (PA05). In this study, the vertical displacement time series recorded by the shallowly anchored GPS antenna are regarded as the true values to assess the accuracy of the subsidence time series recorded by the extensometer. The authors' analysis indicates that the difference between the cumulative subsidence measured by the extensometer and the GPS antenna (PA05) is less than 5 mm for a 17-year span (1996–2012). The RMS of the residuals of the monthly subsidence time series derived from the extensometer and GPS antenna (PA05) data over 13 years (2000–2012) is 2 mm.

The Global Positioning System (GPS) has been used in a variety of applications for which new and more restrictive requirements in the design of the receiving antenna have been introduced. In particular, for high-precision GPS applications, a receiving antenna with superior rejection to multipath signals is required. Furthermore, in order to satisfy the demanded precision and reliability, a high performance GPS antenna must be capable of operation at the two GPS frequencies (1.57542 GHz and 1.2276 GHz). One effective design (see Boccia, L. et al., Microwave and Optical Technology Letters, 2001) demonstrates that consistent multipath mitigation can be obtained with a single frequency shorted annular patch. A stacked shorted elliptical patch, operating at the two GPS bands, is presented. The antenna combines the shorted ring radiation properties, which have proved to comply adequately with multipath mitigation requirements, with dual frequency operations, resulting in a compact high performance dual frequency GPS antenna.

The UK Natural Environment Research Council (NERC) is developing an autonomous underwater vehicle (AUV) capable of measuring, storing and transmitting full-depth oceanographic data over basin-wide tracks. An important feature of this AUV (known as Autosub) is that it will surface periodically for short periods in order to communicate with its base and to determine its position. The satellite-based global positioning system (GPS) has been chosen as the prime candidate for this latter requirement. However, GPS suffers from a number of significant disadvantages in the wet environment of an AUV. The one discussed is the difficulty of acquiring fresh satellite orbital parameters (the ephemeris) in the presence of periodic wave wash-over of the GPS antenna. A collaborative programme involving members of the Autosub team based at the NERC Dunstaffnage Marine Laboratory (DML) and GPS specialists at Navstar Systems Ltd is addressing this problem in two stages. Firstly, the dynamics of the AUV and the consequent antenna masking and interaction with the GPS carrier and code tracking loops have been simulated, leading to the development and validation of a new algorithm for reconstruction of the satellite message. A later stage, not discussed in detail in the present paper, will embed the algorithm in the firmware of a production GPS receiver and test it under practical conditions of signal disruption. The results of the simulation stage are discussed. Some initial work on the development of a simple GPS antenna capable of withstanding immersion to full ocean depth is also presented.

A new sea level observation system has been developed using GPS (Global Positioning System) technique to detect the ocean waves, tide and tsunami before it reaches the coast. The system consists of a buoy on the sea, which has the GPS antenna in the top part, and a GPS antenna on land. We employed real-time kinematic (RTK)-GPS technology to monitor a moving buoy in real-time with an accuracy of a few centimeters by relative positioning. After the basic experiment was carried out in Sagami Bay in 1998, the practical application experiment has been executed at the position about 2km away from the coast of Ofunato city since 23rd January 2001. This paper reports the summary of the new measurement system to observe the sea level, and the findings of an efficiency experiment in the ocean.

This paper presents an adaptive learning method for data fusion in autonomous\ndriving vehicles. The localization is based on the integration of Inertial\nMeasurement Unit (IMU) with two Real-Time Kinematic (RTK) Global Positioning\nSystem (GPS) units in an adaptive Kalman filter (KF). The observability\nanalysis reveals that $i$) integration of a single GPS with IMU does not\nconstitute an observable system; $ii$) integration of two GPS units with IMU\nresults in a locally observable system provided that the line connecting two\nGPS antennas is not parallel with the vector of the measured acceleration,\ni.e., the sum of inertial and gravitational accelerations. The latter case\nmakes it possible to compensate for the error in the estimated orientation due\nto gyro drift and its bias without needing additional instruments for absolute\norientation measurements, e.g., a magnetic compass. Moreover, in order to cope\nwith the fact that GPS systems sometimes lose their signal and receive\ninaccurate position data, the self-tuning filter estimates the covariance\nmatrix associated with the GPS measurement noise. This allows the KF to\nincorporate GPS measurements in the data fusion process heavily only when the\ninformation received by GPS becomes reliably available.\n

The multi-band frequency operation is a property that antennas, utilized in several communication systems, have to exhibit. In this paper, a compact printed antenna for Global Positioning System (GPS) and terrestrial radio services is presented. It is composed via the union of four inverse Koch fractal patches. The antenna operates in three frequency ranges (GPS, Digital Cellular System-DCS1800 and 2.7 GHz). It is driven by two feed probes, directly matched to the radiating element without any matching network to be necessary. At GPS, the antenna is capable of generating a circularly polarized field, with maximum strength at the broadside direction. At the other two frequencies, the field is linearly polarized and the maximum of radiation appears apart from the broadside. Two pins, embedded in the structure, are activated at DCS and at 2.7 GHz in order to enhance the performance of the antenna.

With the Global Positioning System (GPS), it is possible to estimate the baseline vectors between several GPS antennas (with fixed positions on a vehicle) and so, the attitude can be determined. To achieve this, the precise carrier phase measurements are used, however, these measurements have the so called phase ambiguities (integer number of cycles) that need to be solved. When only single-frequency measurements (L1 band) are used, the method known as Ambiguity Filter is employed, after the search method LAMBDA, to stabilize the obtained solution. The leverage of the Ambiguity Filter, relatively to the alternative of using only the LAMBDA method, comes from using a prior knowledge of the baseline length in the ambiguity resolution problem, which the LAMBDA does not. Preliminary tests with the implementation of the Ambiguity Filter have shown that its performance is very sensitive to the precision with which the baseline length is known. This was the main motivation for the work here presented. The results presented in this paper are based on field tests, conducted at the university campus, with two GPS receivers in a static, fixed length, baseline configuration.

Many vehicular emergency call applications utilize a dual-band cellular phone for data exchange and Global Positioning System (GPS) antenna for localization. When the cellular phone antenna is transmitting in close proximity to the GPS antenna, the GPS low-noise amplifier (LNA) is expected to be not affected, i.e., remain linear during the operation. Most commercial GPS LNAs hardly meet this requirement, hence passive antenna-to-antenna isolation and preamplifier filtering without affecting the noise figure of the system becomes crucial. In addition, passive antenna gain requirements for emergency call applications are generally higher than those of regular dual-band cellular phone antennas. To satisfy all these requirements, a multiple-element antenna is designed, built, and measured.

Recent miniaturization and weight reductions of Global Positioning System (GPS) collars have opened up deployment opportunities on a new array of terrestrial animal species, but the performance of lightweight (<90 g) GPS collars has not been evaluated. I examined the success of 42 GPS collars from 3 manufacturers (Televilt/TVP Positioning, AB, Lindesburg, Sweden; Sirtrack Ltd., Havelock North, New Zealand; H.A.B.I.T [HABIT] Research Ltd., Victoria, BC, Canada) in stationary, open‐sky conditions and during deployments on brushtail possums ( Trichosurus vulpecula ), a nocturnal arboreal marsupial. I assessed performance of these collars in terms of technical malfunctions, fix‐success rates, battery longevity, and aspects of location quality. Technical malfunctions occurred in >50% of HABIT and Televilt collars, whereas all Sirtrack collars operated normally. Fix‐success rates for all brands were significantly higher during stationary tests than when deployed on brushtail possums. HABIT and Televilt brands functioned poorly in field conditions, with success rates of 16.2% and 2.1%, respectively. Sirtrack collars had the highest fix rate when deployed (64.8%). I modified several HABIT collars by changing the GPS antenna location, with a resultant substantial increase in field fix success (92.6%). Most collars ceased working before they reached 50% of their manufacturer‐estimated life expectancy. Suboptimal placement of GPS antenna, combined with short satellite acquisition times and long fix intervals, were a likely cause of low fix‐success rates and premature battery failures. Researchers wanting to employ lightweight GPS collars must be aware of current limitations and should carefully consider prospects of low fix rates and limited battery lives before deciding whether these units are capable of meeting study objectives.

The use of a spar buoy equipped with a Global Positioning System (GPS) antenna to calibrate the height measurement of the TOPEX radar altimeter is described. In order to determine the height of the GPS antenna phase center above the ocean surface, the buoy was also equipped with instrumentation to measure the instantaneous location of the waterline, and tilt of the buoy from vertical. The experiment was conducted off the California coast near the Texaco offshore oil platform, Harvest, during cycle 34 of the TOPEX/POSEIDON observational period. GPS solutions were computed for the buoy position using two different software packages, K&RS and GIPSY‐OASIS II. These solutions were combined with estimates of the waterline location on the buoy to yield the height of the ocean surface. The ocean surface height in an absolute coordinate system combined with knowledge of the spacecraft height from tracking data provides a computed altimeter range measurement. By comparing this computed value to the actual altimeter measurement, the altimeter bias can be calibrated. The altimeter height bias obtained with the buoy using K&RS was −14.6±4 cm, while with GIPSY‐OASIS II it was −13.1±4 cm. These are 0.1 cm and 1.6 cm different from the −14.7±4 cm result obtained for this overflight with the tide gauge instruments located on Platform Harvest.

This poster presents the tracking and live-streaming systems developed by the Gannon University High Altitude Ballooning Team in conjunction with NASA (National Aeronautics and Space Administration), Montana University, and other universities used to capture the August 21 solar eclipse. Also described are the preparation activities, launch day procedures, and final results of the Gannon Team’s flight. Four payloads were developed: the Raspberry Pi controlled video payload, the RF (Radio Frequency) and cell phone tracking payload, the still image and Iridium payload, and the cut down payload. The base station consisted of three antennas and laptop for reception and streaming of live video and still image photos. Two tracking vehicles equipped with a GPS (Global Positioning System) unit, RF antenna, and laptop were used to track the balloon and record the path of the tracking vehicles. The MapPoint software package was used to simultaneously plot GPS coordinates received from the RF and GPS antennas. C# code was developed by the Gannon Team to extract and write RF transmitted GPS coordinates to a .csv file inputted into the MapPoint software. Cell phone data was transmitted to AccuTracking.com via mobile hotspot. A switch connected to the RF GPS and microcontroller prevented the phone from transmitting until the payloads landed. Iridium coordinates were retrieved from the Borealis website. All launch day activities including the filling of the balloon and the final preparation and testing of payloads were completed by the Gannon Team. Transportation of equipment from Erie to Kentucky was also done by Gannon.

Misalignment can be an important error source in the integration of the global positioning system (GPS) and inertial navigation systems. This paper presents car test results on the estimation of alignment errors in the integration of a low-grade inertial measurement unit (IMU) with accurate GPS measurement systems. The car test was conducted with a low-cost solid-state IMU and carrier-phase differential GPS measurement systems. Test results showed that changes in the angular velocity improve the estimation of the lever arm between the GPS antenna and IMU. They also showed that changes in acceleration improve the estimation of the relative attitude between the GPS antenna array and IMU. The lever arm was estimated with a 10-cm error. The relative attitude was estimated with a half-degree error. An iterative scheme was used to improve the estimation of the alignment errors during postprocessing. The scheme was shown to be useful when the test car could not have sufficient changes in motion due to limitations in its path. With the given set of test data, the estimation error decreased as the number of iterations increased.

A microstrip patch antenna for Global Positioning System (GPS) application is presented in this study. It has a rectangular shape with two notched slots. The notched slots are introduced to improve the adaptation between the microstrip line and the antenna. The antenna was designed and simulated by CST using FR-4 material as the substrate with relative permittivity of 4.3. The proposed microstrip antenna is designed to operate in the GPS band frequency from 1.555 GHz to 1.595 GHz. The performance analysis of the proposed antennas has been carried out in terms of return loss (dB), gain (dB), and VSWR.

Performance of High-Rate Kinematic GPS During Strong Shaking: Observations from Shake Table Tests and the 2010 Chile EarthquakeOver the last decade, the 1-sample-per-second kinematic Global Positioning System (GPS) has been used as a displacement sensor in earthquake observations and for structural health monitoring. Many researchers in both seismology and engineering have expressed the desire for higher-sample-rate (10-sample-per-second or higher) GPS data to acquire high-frequency displacement information. We performed several shake table tests of GPS observation on 29 April, 2009 for the purpose of evaluating the performance of high-rate kinematic GPS. We found that the accuracy of high-rate kinematic GPS depended on antenna movement, but was independent of receiver sampling rate. The errors in kinematic GPS measurements during the periods of strong shaking were systematically larger than those during the static periods. Furthermore, we found that these large errors were coincident with large accelerations and jerks in the motions experienced by the GPS receivers and antennas. Observations from the 2010 earthquake in Maule, Chile (M 8.8) indicated that strong ground motions can degrade the accuracy of high-rate kinematic GPS measurements. Significant jerks and/or accelerations can cause GPS units to temporarily lose tracking on satellite signals and lead to gaps in GPS-recorded seismograms.