GPS Antenna Research Articles

ONE-STEP AND TWO-STEP CALIBRATION OF A PORTABLE PANORAMIC IMAGE MAPPING SYSTEM

Abstract. A Portable Panoramic Image Mapping System (PPIMS) is proposed for rapid acquisition of three-dimensional spatial information. By considering the convenience of use, cost, weight of equipment, precision, and power supply, the designed PPIMS is equipped with 6 circularly arranged cameras to capture panoramic images and a GPS receiver for positioning. The motivation for this design is to develop a hand-held Mobile Mapping System (MMS) for some difficult accessing areas by vehicle MMS, such as rugged terrains, forest areas, heavily damaged disaster areas, and crowed places etc. This PPIMS is in fact a GPS assisted close-range photogrammetric system. Compared with the traditional close-range photogrammetry, PPIMS can reduce the need of ground control points significantly. Under the condition of knowing the relative geometric relationships of the equipped sensors, the elements of exterior orientation of each captured image can be solved. However, the procedure of a system calibration should be done accurately to determine the relative geometric relationships of multi-cameras and the GPS antenna center, before the PPIMS can be applied for geo-referenced mapping. In this paper, both of one-step and two-step calibration procedures for PPIMS are performed to determine the lever-arm offsets and boresight angles among cameras and GPS. The performance of the one-step and two-step calibration is evaluated through the analysis of the experimental results. The comparison between these two calibration procedures was also conducted. The two-step calibration method outperforms the one-step calibration method in terms of calibration accuracy and operation convenience. We expect that the proposed two-step calibration procedure can also be applied to other platform-based MMSs.

Calibration of Envisat radar altimeter over Lake Issykkul

This study presents the results of calibration/validation (C/V) of Envisat satellite radar altimeter over Lake Issykkul located in Kyrgyzstan, which was chosen as a dedicated radar altimetry C/V site in 2004. The objectives are to estimate the absolute altimeter bias of Envisat and its orbit based on cross-over analysis with TOPEX/Poseidon (T/P), Jason-1 and Jason-2 over the ocean. We have used a new method of GPS data processing in a kinematic mode, developed at the Groupe de Recherche de Geodesie Spatiale (GRGS), which allows us to calculate the position of the GPS antenna without needing a GPS reference station. The C/V is conducted using various equipments: a local GPS network, a moving GPS antenna along the satellites tracks over Lake Issykkul, In Situ level gauges and weather stations. The absolute bias obtained for Envisat from field campaigns conducted in 2009 and 2010 is between 62.1 and 63.4±3.7cm, using the Ice-1 retracking algorithm, and between 46.9 and 51.2cm with the ocean retracking algorithm. These results differ by about 10cm from previous studies, principally due to improvement of the C/V procedure. Apart from the new algorithm for GPS data processing and the orbit error reduction, more attention has been paid to the GPS antenna height calculation, and we have reduced the errors induced by seiche over Lake Issykkul. This has been assured using cruise data along the Envisat satellite track at the exact date of the pass of the satellite for the two campaigns. The calculation of the Envisat radar altimeter bias with respect to the GPS levelling is essential to allow the continuity of multi-mission data on the same orbit, with the expected launch of SARAL/Altika mission in 2012. Implications for hydrology in particular, will be to produce long term homogeneous and reliable time series of lake levels worldwide.

Analysis of Hydrodynamic Noise around Acoustic Modem on the AUV Using Hybrid LES-Lighthill Method

Acoustic modem is one of the most important sensors on the deep sea AUV. A good performance of the acoustic modem has great effect on the safety and operation of deep sea AUV. According to the construction of deep sea AUV, acoustic modem is installed in the cavity behind the GPS antenna, it would cause flow noise around the acoustic modem and thus interference will occur when the communication is established between deep sea AUV and surface. Flow-induced noise around the acoustic modem is studied in this paper. Firstly the unsteady flow around the acoustic modem is studied by large eddy simulation (LES) method. Secondly based on the resolved information of flow field, acoustic noise distribution is studied using equivalent acoustic sources method. Compared with different positions of GPS antenna, flow noise distribution around the acoustic modem and the effect on communication is investigated. Then acoustic modem layout on the AUV is optimized.

Research Activities in Precise Positioning at Laval University

This review paper summarises the recent, on-going, and future research activities in precise positioning at Laval University. The projects undertaken by the GPS and Geodesy Research Group are presented following three main research topics. The first one deals with the use of precise positioning for deformation monitoring of engineering structures. The study of ice forces on dams using a robotic total station and the improvement of GPS height determination using multiple GPS antennas linked to a single receiver with calibrated fiber optics are presented. A second topic of research is the crustal deformation of the Charlevoix seismic zone in Quebec. This study uses GPS and levelling techniques and involves an investigation of the temporal stability of the GPS permanent stations available in the surrounding area. Finally, research on single GPS receiver positioning techniques is presented, namely, Precise Point Positioning (PPP) and Time Relative Positioning (TRP).

The use of civilian-type GPS receivers by the military and their vulnerability to jamming

We considered the impact of external influences on a GPS receiver and how these influences affect the capabilities of civilian-type GPS receivers. A standard commercial radio frequency signal generator and passive GPS antenna were used to test the sensitivity of GPS to intentional jamming; the possible effects of the terrain on the propagation of the jamming signal were also tested. It was found that the high sensitivity of GPS receivers and the low strength level of GPS satellite signals combine to make GPS receivers very vulnerable to intentional jamming or unintentional radio frequency interference. Terrain undulation was used to shield GPS antennas from the direct line-of-sight of the jamming antenna and this indicated that terrain characteristics can be used to mitigate the effects of jamming. These results illuminate the vulnerability of civilian-type GPS receivers to the possibility and the ease of disablement and establish the foundation for future work.

On simulation of precise orbit determination of HY-2 with centimeter precision based on satellite-borne GPS technique

The HY-2 satellite carrying a satellite-borne GPS receiver is the first Chinese radar altimeter satellite, whose radial orbit determination precision must reach the centimeter level. Now HY-2 is in the test phase so that the observations are not openly released. In order to study the precise orbit determination precision and procedure for HY-2 based on the satellite-borne GPS technique, the satellite-borne GPS data are simulated in this paper. The HY-2 satellite-borne GPS antenna can receive at least seven GPS satellites each epoch, which can validate the GPS receiver and antenna design. What’s more, the precise orbit determination processing flow is given and precise orbit determination experiments are conducted using the HY-2-borne GPS data with both the reduced-dynamic method and the kinematic geometry method. With the 1 and 3 mm phase data random errors, the radial orbit determination precision can achieve the centimeter level using these two methods and the kinematic orbit accuracy is slightly lower than that of the reduced-dynamic orbit. The earth gravity field model is an important factor which seriously affects the precise orbit determination of altimeter satellites. The reduced-dynamic orbit determination experiments are made with different earth gravity field models, such as EIGEN2, EGM96, TEG4, and GEMT3. Using a large number of high precision satellite-borne GPS data, the HY-2 precise orbit determination can reach the centimeter level with commonly used earth gravity field models up to above 50 degrees and orders.

Some problems of GPS RTK technique application to mining subsidence monitoring

Owing to the variability of mine surfaces, it is difficult to obtain the deformation monitoring data of the observation stations by traditional leveling technique. GPS RTK (Real-Time Kinematic) technique was employed to the subsidence observation in this paper, and its main sources of errors including rover pole deflection of the vertical, un-modeled systematic errors (gross error, multipath delay etc.) and the height transformation error, were analyzed systematically. Based on the fundamental theories of spherical fitting and Empirical Mode Decomposition (EMD), the error reduction models were studied exhaustively. And two experiments were done in different environment to test the proposed models. The results show that the proposed methods can achieve a fourth-grade leveling accuracy, with (Root-Mean-Square) RMS in three orthogonal directions (N, E and H) of 4.1, 3.3 and 3.1 mm, respectively, by 3–5min continuous shaking of the observation GPS antenna, fully satisfying for mine surface subsidence deformation monitoring.

Attitude determination algorithms for spinning satellites using single antenna GPS receiver and MEMS gyro

This paper proposes a new subsystem of attitude determination for spin-stabilized satellites, which makes use of information from single antenna GPS receiver and a MEMS gyro. The incremental carrier phase state equation and measure model for spinning satelliteʼs attitude motion are derived. The subsystem senses attitude by demodulation of periodic oscillations of the GPS carrier phase caused by satelliteʼs spinning motion with the aid of a MEMS gyro. Numerical examples for spin-stabilized satellites with and without nutation motion are carried out to validate the algorithm. Five key parameters which affect the attitude sensing accuracy are analyzed at last.

Evaluation of a Statistical Model for the Characterization of Multipath Affecting Mobile Terminal GPS Antennas in Sub-Urban Areas

This paper describes and validates a technique to characterize the environmental effects on mobile terminal GPS antennas using statistical model. This method requires the knowledge of 3-D free space antenna gain patterns and average angular distribution of incident power in the environment. The power distribution must be known in both elevation and azimuth and separately for parallel and perpendicular polarizations. The antenna performance is assessed in terms of GPS Mean Effective Gain <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$({\rm MEG}_{\rm GPS})$</tex></formula> and GPS Coverage Efficiency <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$(\eta_{c})$</tex></formula> .

A Novel On-Glass GPS Antenna for Handset Applications

In this paper, we propose a novel on-glass antenna with a planar structure for the GPS wireless communication. A prototype of the proposed antenna with a compact size of 6mm×18mm is experimented in the mobile handset operation. The antenna shows operating bandwidths (referenced Return loss -6dB) for covering the GPS L1 band in 1.575GHz. The present design mainly focuses on the current trends in the development of compact and low profile mobile handset. For reducing the dimension of the antenna area in the device, the GPS antenna is placed on the inner surface of the glass over the display. Moreover, the antenna design can be against to avoid the degradation in the user handheld condition. The simulated and measured data including return loss, antenna gain and radiation patterns are presented. As a result of the measurement, the antenna design is proper to the GPS band application in the mobile handset.

DUAL-BAND CIRCULARLY POLARIZED ANTENNA WITH LOW WIDE-ANGLE AXIAL-RATIO FOR TRI-BAND GPS APPLICATIONS

This paper presents the design of a dual-band microstrip antenna with low wide-angle axial-ratio. The antenna is designed for global positioning satellite operations at 1227MHz (L2), 1575MHz (L1) and 1176MHz (L5, available after 2007). This antenna has another advantage of a much wider band in both VSWR and 3dB axial-ratio compared with single-fed GPS antennas. Details of the design, simulated and experimental results of this GPS antenna are presented and discussed. The measured results conflrm the validity of this design, which meet the requirement of GPS applications.

Analysis of Attitude Determination Methods Using GPS Carrier Phase Measurements

If three or more GPS antennas are mounted properly on a platform and differences of GPS signals measurements are collected simultaneously, the baselines vectors between antennas can be determined and the platform orientation defined by these vectors can be calculated. Thus, the prerequisite for attitude determination technique based on GPS is to calculate baselines between antennas to millimeter level of accuracy. For accurate attitude solutions to be attained, carrier phase double differences are used as main type of measurements. The use of carrier phase measurements leads to the problem of precise determination of the ambiguous integer number of cycles in the initial carrier phase (integer ambiguity). In this work two algorithms (LSAST and LAMBDA) were implemented and tested for ambiguity resolution allowing accurate real‐time attitude determination using measurements given by GPS receivers in coupled form. Platform orientation was obtained using quaternions formulation, and the results showed that LSAST method performance is similar to LAMBDA as far as the number of epochs which are necessary to resolve ambiguities is concerned, but with processing time significantly higher. The final result accuracy was similar for both methods, better than 0.1° to 0.2°, when baselines are considered in decoupled form.

1A2-B08 複数の一周波GPS受信機を用いた小型UAVの高精度姿勢計測(3次元計測/センサフュージョン(2))

This paper describes an attitude determination technique for small UAVs (Unmanned Aerial Vehicles). Small UAVs are attracted the attention for effective means of the collecting aerial information. However, there are few practical applications, because the accurate attitude data cannot be obtained due to its small payloads. We propose the attitude determination technique using the multiple single frequency GPS receivers. We install three GPS antennas on the wing of the UAV. We resolve the integer ambiguity of the carrier frequency of GPS observation data using the geometric constrain of the antennas to estimate the attitude of the UAV. In the result of the static test, we conclude the proposed method is effective to estimate the attitude for the small UAV.

Cultural Heritage Recording Utilising Low-Cost Closerange Photogrammetry

Cultural heritage is under a constant threat of damage or even destruction and comprehensive and accurate recording is necessary to attenuate the risk of losing heritage or serve as basis for reconstruction. Cost effective and easy to use methods are required to record cultural heritage, particularly during a world recession, and close-range photogrammetry has proven potential in this area. Off-the-shelf digital cameras can be used to rapidly acquire data at low cost, allowing non-experts to become involved. Exterior orientation of the camera during exposure ideally needs to be established for every image, traditionally requiring known coordinated target points. Establishing these points is time consuming and costly and using targets can be often undesirable on sensitive sites. MEMS-based sensors can assist in overcoming this problem by providing small-size and low-cost means to directly determine exterior orientation for close-range photogrammetry. This paper describes development of an image-based recording system, comprising an off-the-shelf digital SLR camera, a MEMS-based 3D orientation sensor and a GPS antenna. All system components were assembled in a compact and rigid frame that allows calibration of rotational and positional offsets between the components. The project involves collaboration between English Heritage and Loughborough University and the intention is to assess the system’s achievable accuracy and practicability in a heritage recording environment. Tests were conducted at Loughborough University and a case study at St. Catherine’s Oratory on the Isle of Wight, UK. These demonstrate that the data recorded by the system can indeed meet the accuracy requirements for heritage recording at medium accuracy (1-4cm), with either a single or even no control points. As the recording system has been configured with a focus on low-cost and easy-to-use components, it is believed to be suitable for heritage recording by non-specialists. This offers the opportunity for lay people to become more involved in their local heritage, an important aspiration identified by English Heritage. Recently, mobile phones (smartphones) with integrated camera and MEMS-based orientation and positioning sensors have become available. When orientation and position during camera exposure is extracted, these phones establish off-the-shelf systems that can facilitate image-based recording with direct exterior orientation determination. Due to their small size and low-cost they have potential to further enhance the involvement of lay-people in heritage recording. The accuracy currently achievable will be presented also.

Snow measurement by GPS interferometric reflectometry: an evaluation at Niwot Ridge, Colorado

AbstractSnow is a critical storage component in the hydrologic cycle, but current measurement networks are sparse. In addition, the heterogeneity of snow requires surveying larger areas to measure the areal average. We presented snow measurements using GPS interferometric reflectometry (GPS‐IR). GPS‐IR measures a large area (~100 m2), and existing GPS installations around the world have the potential to expand existing snow measurement networks. GPS‐IR uses a standard, geodetic GPS installation to measure the snow surface via the reflected component of the signal. We reported GPS‐IR snow depth measurements made at Niwot Ridge, Colorado, from October 2009 through June 2010. This site is in a topographic saddle at 3500 m elevation with a peak snow depth of 1.7 m near the GPS antenna. GPS‐IR measurements are compared with biweekly snow surveys, a continuously operating scanning laser system and an airborne light detection and ranging (LIDAR) measurement. The GPS‐IR measurement of peak snowpack (1.36–1.76 m) matches manual measurements (0.95–1.7 m) and the scanning laser (1.16 m). GPS‐IR has RMS error of 13 cm (bias = 10 cm) compared with the laser, although differences between the measurement locations make comparison imprecise. Over the melt season, when the snowpack is more homogenous, the difference between the GPS‐IR and the laser is reduced (RMS = 9 cm, bias = 6 cm). In other locations, the GPS and the LIDAR agree on which areas have more or less snow, but the GPS estimates more snow on the ground on tracks to the west (1.58 m) than the LIDAR (1.14 m). Copyright © 2011 John Wiley &amp; Sons, Ltd.

A Novel Method to Measure Array Manifolds of GNSS Adaptive Antennas

: We present a procedure for measuring the complete, in situ array manifold of a STAP-based adaptive antenna using only standard GNSS receiver measurements. Note that one needs in situ array manifolds in adaptive spatial processing as well as for estimation of the antenna induced biases in GNSS measurements. The proposed procedure is a straightforward extension of traditional outdoor GPS antenna calibration methods. The adaptive filter weights in the antenna electronics are carefully varied, and their effect on the GNSS receiver measurements are recorded. Using a system of equations derived in this paper, these receiver measurements are used to solve for the frequency response of each antenna element in each satellite direction. The accuracy of the proposed procedure is established using computer simulations. We also show that the measured array manifolds provide a very good estimate of the antenna induced biases in GNSS receiver measurements in the presence of interferers.

Design of GPS Based on Single Chip Microcomputer

In order to go on a journey conveniently, the STC89C52 SCM is used, one kind of GPS user terminal is designed, it including GM-89 GPS module, communications and transformation connection, control processing electric circuit, display circuit, RS232 exterior serial communication connection and so on. The related hardware welding on the PCB, the software programming After-Burning writes in the SCM, inserts the TFT colored tablet (or 12864 liquid crystals) and outside sets at the type GPS antenna. On the electricity, demonstrated the longitude, latitude, time and altitude above sea level and so on information, after access the internet to consult the local latitude and longitude information to carry on compared to rightly, the result is correct, indicated that has achieved the design requirements.

Dual band dual sense circularly polarised monopole antenna for GPS and WLAN applications

A novel circular dual band, dual sense circularly polarised (CP) monopole antenna for GPS and WLAN applications is presented. A CP bandwidth larger than 40% can be attained simply by creating rectangular slots on the circular patch of the microstrip line. By adding rectangular slots, the 3 dB axial ratio bandwidth and the −10 dB impedance bandwidth can be greatly improved. Novel and simple design of the radiating patch, large 3 dB axial ratio bandwidth and compact size of the antenna are the novel aspects of this work.

Design of Single-Feed Dual-Frequency Patch Antenna for GPS and WLAN Applications

A design of single-feed dual-frequency patch antennas with different polarizations and radiation patterns is proposed. The antenna structure is composed of two stacked patches, in which the top is a square patch and the bottom is a corner-truncated square-ring patch, and the two patches are connected together with four conducting strips. Two operating frequencies can be found in the antenna structure. The radiations at the lower and higher frequencies are a broadside pattern with circular polarization and a conical pattern with linear polarization, respectively. A prototype operating at 1575 and 2400 MHz bands is constructed. Both experimental and simulated results show that the prototype has good performances and is suitable for GPS and WLAN applications.

컨테이너 보안 장치(ConTracer)에 활용되는 2.45GHz 안테나에 대한 성능 검증

본 논문에서는 컨테이너화물 안전수송에 사용되는 ConTracer장치에 활용할 2.45GHz 및 GPS 통합 안테나 보드를 설계 및 검증하고자 한다. 설계된 통합 안테나 보드는 컨테이너 도어에 적용하고자 컨테이너 도어에 해당되는 모형 모델링하여 철재물에 대한 RF 영향에 대해 시뮬레이션 하여 그 결과를 반영하여 2.45GHz 안테나와 GPS 안테나를 설계하였다. 본 논문에서는 컨테이너 도어 부분만 모델링하여 컨테이너 환경에 초점을 맞춰 최적의 안테나 파라미터들의 성능이 구현될 수 있도록 2.45GHz 안테나와 세라믹 재질로 만든 GPS 안테나를 통합 보드로 제작하여 그 특성을 검증하였다. In this paper, A Design of 2.45GHz and GPS antenna Integrated Board using Container security Device(ConTracer) for container cargo transportation is proposed and experimentally evaluate. Integrated antenna board include 2.4GHz chip and Ceramic GPS antenna is also consider the impact of RF interference based on simulation for applied to steel container. After a careful comparison and analysis a part of the container door for its best performance, We conduct tests to characterize. The proposed integrated antenna board is suitable for container cargo transportation application in steel container field.