2005 Abstracts


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Vol. 38, No. 298. October 2005

1. Position errors caused by GPS height of instrument blunders
T. H. Meyer and A. L. Hiscox

Height of instrument (HI) blunders in GPS measurements cause position errors. These errors can be pure vertical, pure horizontal, or a mixture of both. There are different error regimes depending on whether both the base and the rover both have HI blunders, if just the base has an HI blunder, or just the rover has an HI blunder. The resulting errors are on the order of 30 cm for receiver separations of 1000 km for an HI blunder of 2 m. Given the complicated nature of the errors, we believe it would be difficult, if not impossible, to detect such errors by visual inspection. This serves to underline the necessity to enter GPS HIs correctly.

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2. Increasing reliability of the test for outliers whose magnitude is small
Serif Hekimoglu

The power and level breakdown points measure the global reliability of a test in robust statistics. However, they cannot give enough information about the reliability of a test if outliers are small. Hence, mean success rate (MSR) of a test for outliers (such as data snooping, * ?test) was introduced. But, the MSRs of tests for outliers are small. To increase the MSRs of tests for outliers, we propose a new repetitive test procedure where the weights of the randomly chosen observations are increased to the same large value such as 4. is the number of all possible outliers. The test procedure is repeated for a given number of times and tested on a linear regression by a simulation. One hundred generated samples with random errors distributed normally were chosen. Random and influential outliers are considered in the tail regions and in the whole region of a sample. These outliers are randomly generated 100 times for each simulated sample. Repeating the new test procedure only 20 times, the MSR of data snooping and also the MSR of *?test are increased for one outlier lying between 3? and 6? at a rate of 10% and 20% respectively.

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3. Using GPS near the forest and quality control
A. Pirti

This paper attempts to provide some insights into the fading properties of GPS signals. When a GPS signal reaches the antenna, it suffers from masking and blocking effects from surrounding objects. With respect to these effects, GPS signals can be divided into clear signals, shadowed signals, and blocked signals.
In this article we shall examine the performance and use of GPS based data acquisition systems near forest. As a general rule, a clear view of the sky is preferred when using GPS for determining location. This means that using GPS near forest is one of the most demanding uses of technology and one that requires particular attention when evaluating GPS receivers that will be used in such an environment.
The signal transmitted by GPS satellites are extremely low power, and the GPS signal is about 100 times weaker than the general background radiation at that frequency. The signal passing through your body right now from a local television or radio station is almost certainly several thousand times stronger than a GPS signal. GPS receivers use sophisticated signal processing techniques to lock onto and track the GPS satellites. However, the relatively low power of these signals can indeed pose problems when the signal is further degraded by a forest canopy.
Humidity of the leaves and the forest is the critical factor for GPS performance near the forest area. Water laden leaves of tree attenuate more signal than those that are dry. GPS signals will be present with weak signal strengths and positions that are computed from weak signals tend to be less accurate.
This paper evaluates GPS positional accuracy, precision and performance near forest areas. As a result of this attenuation, positions are computed from weak signals and tend to be less accurate.

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4. Robust-type biased estimation in Gauss-Markov model
Gui Qing-ming Li Guo-zhong and Ou Ji-kuen

The parameter estimation problem in Gauss-Markov model is considered when multi-collinearity and outliers exist simultaneously. A class of new estimators, robust-type generalized shrunken estimators, is proposed by grafting robust estimation technique into philosophy generalized shrunken estimation. Many useful and important estimators such as robust-type ordinary ridge estimator, robust-type principal components estimator and so on are obtained by appropriate choices of the shrinking parameter matrix. An algorithm for computing the robust-type generalized shrunken estimate is established. A numerical example is provided to illustrate that these new estimators can not only effectively overcome difficulty caused by multi-collinearity but also resist the influence of outliers.

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5. Independent control of GPS networks above long tunnels by astronomically determined azimuths or bearing angles
N Solaric, Z Versic and D Spoljaric

At the Faculty of Geodesy, University of Zagreb, the automatic astronomical method of determining the azimuth by observing stars and the Sun has been developed within the frame of the scientific work. The classical astronomical method of azimuth determination is rather uneconomical because of extensive field measurements and long-lasting processing. The automation of measuring procedures and processing has enabled the application of the astronomical method in everyday surveying practice, and also in determining the tunnel cut direction, in the independent control of microtrilateration and GPS networks above tunnels. The importance of such an independent control of geodetic networks above tunnels lies in the fact:
1. That we control the relative positional relationships of the points at the entrance, and the exit of a tunnel, respectively,
2. That we control whether the exact value the deflection of the vertical have been taken into
account. Namely, the deflection of the vertical at the points for traverse orientation used for
entering the tunnel can be remarkable which can largely influence the traversing orientation,
especially if the orientation sighting lines are steep.
Applying the astronomical determination of azimuth as an independent control of trilateration or GPS networks over long tunnels, the surveyors can expect with more confidence that the tunnel be cut without any problems.

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6. Evaluation of National Land Administration System in Switzerland. Case study based on a management model

D. Steudler and I P Williamson

Currently there are no internationally accepted methodologies to evaluate and compare the performance of land administration systems. To engage in this discussion, the authors published a previous article proposing an evaluation framework, which – based on a management model – links the operational aspects of land administration with land policy. In this new article, the framework is being applied to a case study evaluating the national land administration system of Switzerland. The case study puts the earlier developed framework to the test and at the same time gives an insight into the specific national system.

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7. Effects of observation plan and precision on the duration of outliers detection and fuzzy logic: a real network application
H. Konak, A. Dilaver and E. Öztürk

During the total evaluation of measurements, it is aimed to identify the outliers, which distorts the certain values considering all measurement. In this manner, the determination of the best method to form the outlier sets is also considered another problem. Due to its structure Fuzzy Logic approach keeps the observation plan and precision unchanged during the process of outlier identification. The approach mentioned is suggested as a usable method due to its properties. In this paper, a real geodetic network is tested using three different network models. The locations of outliers are searched by fuzzy logic approach, and the success of the method is compared with those of other alternative methods.

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Vol. 38, No. 297. July 2005

1. Diagnosis of outlier of type Multipath in GPS Pseudo-range Observations
J. L. Awange

The nonlinear Gauss-Jacobi algorithm which exploits the capability of algebraic tools of Groebner basis and Multipolynomial resultants to solve in a closed form polynomial system of GPS pseudo-range equations is here proposed as a possible tool for detecting the satellite, whose pseudo-range has been contaminated by the error of type Multipath. By injecting gross errors of 200m and 500m on the pseudo-range observations from two satellites, it is demonstrated how the Gauss-Jacobi combinatorial algorithm detects the falsified satellite and in addition identifies poor geometrical combination of the satellites, which is normally identified via PDOP. Indeed, the Gauss-Jacobi combinatorial algorithm proposed is a straightforward tool, which adopts a deterministic approach that deviates from the statistical stochastic approaches to outlier detection. Outliers are simply detected based on the combinatorial approach first proposed by C. F. Gauss in 1828 and published posthumously but which C. G. I. Jacobi later independently published in 1841. The computing engine for the Gauss-Jacobi combinatorial algorithm, Groebner basis or Multipolynomial resultant algorithms for computing pseudo-ranges have already been prepared by J. L. Awange and E. W. Grafarend and can be accessed in the GPS toolbox via http://www.ngs.noaa.gov/gps-toolbox/awange.htm. The proposed algebraic approach proves to be a powerful tool in detecting outliers and could be applied not only to GPS pseudo-range problem but to any problem that permits the conversion of its system of equations into algebraic (polynomial form). This is demonstrated using the planar ranging problem.

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2. Precision and Results Reliability Analysis of different instruments for investigating vertical micro-displacement of structures
D.B.Kovacic and D.Z.Kapovic

This paper presents an analysis of the precision and results reliability of different instruments when researching the vertical displacements of objects in a space. In Slovenia the researching at objects by pressure testing is obligatory for all structures longer than 15 metres (JUS U.M1.046). We chose both geodetic and non-geodetic methods. There are many methods for researching displacements, so we limited it to the instruments available to us. The Faculty of Civil Engineering, University of Maribor, Slovenia, uses the total station, level, and the inductive transducer and laser level. The displacement measurements were made on a reinforced concrete plate, type PVP5. We calculated the foreseen displacements by the analytic as well numeric method for the plate. We used the National regulations (Euro code 2) for analytic calculation and for the numeric part we used the Ocean program. We calculated the standard deviation and the optimal accuracy for each instrument, we also checked the significance of the results by an analysis of the variances with one variable factor and by using the “Baarda’s data snooping” method we also did a check for the presence of rough mistakes that can occur in the measurement results.
In this paper we describe all the instruments for following the displacements and the working principles of the instruments with which the research was carried out, and the measurement errors.
The precision analysis was made on the basis of a comparison between the results of the foreseen displacements and the gained results of the measurements. The results of this research are collated in the conclusion and give us the answers to our goals.

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3. A Computational approach to the Robinson Projection
C. Ipbuker

The Robinson projection is the most preferred world map projection in the atlas cartography. There are no analytical formulas except Robinson’s look-up table for this projection. This deficiency has led a number of requests for the plotting formulas and cartographers have studied to derive analytical equations using different algorithms. In these works, different interpolation algorithms are applied to Robinson’s table values and solutions are presented including some critics about the deformations on this projection. In this study, a summary of these computation algorithms is collected. The multiquadric interpolation method is suggested and applied to the Robinson’s tabular coordinates. A series of numerical evaluations are presented then for the controversies and for comparison between these computation algorithms.

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4. PDOP values for simulated GPS/Galileo Positioning

Peter Cederholm

The paper illustrates satellite coverage and PDOP values for a simulated combined GPS/Galileo system. The designed GPS satellite constellation and the planned Galileo satellite constellation are presented. The combined system is simulated and the number of visible satellites and PDOP values are estimated at 4140 points around the earth. The simulation that is carried out with a 15 degrees cut-off angle is repeated every 10 minutes for 72 hours. The simulation shows that mean PDOP values are improved significantly when using a combined system compared to using only GPS.

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5. Modelling landslide surfaces by kinematic and dynamic surface models: a case study in North Eastern Turkey
M. Yalçinkaya , T. Bayrak and A. Yalçin

Landslides occurring over time can be visually monitored by surface models. In addition, point movements that have not been measured can be determined with these models using extrapolation. There are several surface models including kinematic and dynamic. In the kinematic surface model, the surface is determined as dependent on time. In the dynamic surface model, the surface is determined regarding cause of movement in addition to time. Landslides are not simple two-dimensional features but have a three-dimensional form and a complicated temporal context. They are dynamic systems that are complex in time and space. Therefore, in this study, a dynamic surface model regarding the cause of landslides was developed to monitor landslides and determine movement surface.
Kutlugün Village, a landslide-prone area in Maçka County in the Province of Trabzon in Eastern Black Sea Region of Turkey, was selected for the study. Geological and geophysical investigations were made and it was determined that the change in the groundwater level was the most important cause of landslides. Groundwater level changes were taken into account in the formation of the dynamic surface model. Groundwater levels were measured at three bore holes and at two geophysical points. In addition, a geodetic control network covering the whole region and its surroundings was established. The point coordinates were determined by GPS. Using this data, a dynamic surface model was developed. The model includes computations of surface coefficients and groundwater effect coefficients. Through this model, dynamic surfaces were determined for the measurement periods. For the same measurements periods, kinematic surfaces were also determined. The results derived from both models were compared. It can be seen that groundwater changes affected surface changes. These surface changes which occurred over time were determined more realistic by the dynamic surface model

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6. Determination of the optimal diameter for spherical targets used in 3D laser scanning
Yuriy Reshetyuk, Milan Horemuž and Lars E. Sjöberg

An efficient use of 3D laser scanning requires the development of standardized calibration procedures available to the users. This is part of the research recently started at the Royal Institute of Technology (KTH) in Stockholm and the establishment of a calibration field is planned, which may be realized by means of spherical targets. An approach for the rigorous theoretical determination of the optimal diameter for those targets is presented. It is based on the least-squares adjustment according to the mixed model when observations are combined with the unknown parameters. The weight function was chosen based on the Lambertian standard reflectance model. The computations were performed for the scanners Leica HDS 3000 and Imager 5003 (Zoller+Fröhlich) for two cases – with fixed and “free” (to be estimated in the adjustment) target diameter. The value of 14 cm has been obtained for the optimal diameter, which is independent on the range to the scanner.

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7. The influence of the sea on driving the Channel Tunnel
A Johnston

Due to a small lack of symmetry between the left and right hand wall bracket survey stations in relation to the tunnel centreline and a difference between left and right sides in the array of pipes and cables on the walls, the airflow differed between the sides of the tunnel. This, and the annual sea temperature variation, produced a small but detectable effect on the tunnel setting out survey.

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Vol. 38, No. 296. April 2005

1. Augmenting GPS by ground-based pseudolite signals for airborne surveying applications
Hung Kyu Lee, Jinling Wang, Chris Rizos and Toshiaki Tsujii

This paper discusses some issues associated with the implementation of ground-based pseudolite augmentation for GPS airborne surveying applications. For instance, not only should two antenna offsets (one on the top of, and the other underneath, the platform) be corrected for, but the number, the location, and the geometric distribution of the pseudolites on the ground has to be carefully considered. Initial analyses have shown that the accuracy requirement for the attitude parameters is dependent on the magnitude of the offsets between the two antennas. In addition, a series of simulations has demonstrated that pseudolite augmentation can significantly improve the quality of the positioning solutions, especially the vertical component accuracy (due to the negative elevation of the pseudolites). The optimal number and locations of the pseudolites are dependent on the satellite geometry. Based on selected optimization criteria, a comprehensive search would typically be needed for a specific application. A geometric analysis and measurement testing procedure for this purpose will be described in this paper.

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2. On the quality of distance measurements in athletics throwing events
M. Tsakiri, M. P. Stewart, A. Snow and J. Karabelas

Distance measurement in athletic throwing events is fundamentally a surveying problem which should follow the appropriate quality control procedures. This paper discusses the measurement procedure adopted by the IAAF (International Association of Athletics Federations) for throwing events, with particular emphasis on the javelin event. Published National Survey Standards are applied to form models of the errors associated with the IAAF procedure. The effect of these random error models on measured throwing distances is discussed statistically with probabilities of ‘miscarriages of justice’ (one athlete throwing less far than another but being awarded a longer distance by the officials) being presented. Finally some comments and recommendations regarding the IAAF measurement specifications are made.

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3. A new approach to the iterative calculation of geodetic latitude and its application
J. Pollard

A new approach to the determination of the geodetic latitude of a point from the size of a geocentric ellipse which passes through the point is introduced. It produces a solution from the geocentre out and is shown to improve the efficiency of existing iterative methods.

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4. Applying the theory of planned behaviour to cadastral
Michael Barry

Planners of cadastral systems need to predict how formalising land rights will affect communities that are supposed to benefit from them. In particular, it is important to evaluate if the intended beneficiaries are likely to use the cadastral system. If they do not, addressing the consequences may be costly in time, money and resources. The theory of planned behaviour was adapted, developed and tested as a framework for analysing and predicting land registration and legal boundary usage in a number of urban settlements in Cape Town, South Africa. A study of the upgrading of the Marconi Beam informal settlement to a formal housing project confirmed existing theory – that is, when dealing with informal settlements, predictive models such as the theory of planned behaviour should be applied with caution. The complex social and political dynamics of informal settlements suggest that in volatile situations investigations should include comparative case studies of actual usage behaviour. Otherwise, the results are not likely to serve as an accurate predictor of usage of the cadastral system. However, the theory of planned behaviour does provide a structure for designing a study and it provides the classes of data that should be collected and analysed.

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5. Pedal hyper-surfaces and DOP factors in GPS
A. Antonopoulos and D. Antonopoulou

The hyper-volume “enclosed” by the standard error pedal hyper-surface is a proper measure of total uncertainty in multi-dimensional determination (usually) of positioning. This quantity -especially of use in GPS positioning- is upper bounded by a handy function of the associated DOP factor and minimized, for a given DOP factor, if and only if the precision of positioning is independent of “direction”.

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6. Monitoring vertical movements in Mount Carmel by means of GPS and precise levelling
G. Even-Tzur and E. Agmon

Mount Carmel fault is one of the major geological structures in northern Israel, characterized by intense, continuous, and potentially hazardous seismic activity.
A small monitoring network, spanning an area of 40 by 30 km. and consisting of 17 points, was constructed. Four sets of GPS measurements were taken between 1990 and 1999 as well as two campaigns of precise levelling. Two-Step analysis of the GPS measurements was carried out to quantify recent vertical tectonic deformations.
Strict analysis of the GPS and the levelling data shows significant vertical movements in the area. Two independent methods are pointing to the same vertical behaviour at the monitored region, indicating that the Carmel range uplifts at a rate of 5 mm per year relative to its surroundings.

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7. Cumulative estimation in semi-parametric models
Hongchang Hu Haiyan Sun

This paper considers a particular semi-parametric model Firstly, the cumulative estimation method of linear model is applied to the semi-parametric model, moreover, a general weight function is chosen as the non-parametric estimator. Both estimators are obtained. Secondly, some statistical properties of estimators are discussed. Finally, an example is imitated, which shows validity of the cumulative method.

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8. Improving an algorithm for total electron content estimation: experiments from Esfahan
Vahab Nafisi, Mehran Sattari, and Mehdi Momeni Shahraki

It is possible to use single frequency GPS receivers to estimate the Total Electron Content (TEC). In this research, we improved an algorithm presented by Giffard [2], that is based on a least squares solution. We investigated the effect of the use of different weights (elevation of satellites, signal to noise ratio, combination of elevation and signal to noise ratio) and different block sizes on TEC estimates. We found that these parameters had a significant impact on TEC estimates based on this algorithm. Our research is based on observations at the GPS site of the Esfahan University made with single frequency 12-channel Leica System 500 receivers.

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Vol. 38, No. 295. January 2005

1. Multipath mitigation by Wavelet analysis for GPS base station applications
Chalermchon Satirapod and Chris Rizos

It is well known that multipath disturbance is one of the major error sources impacting on high precision GPS positioning. The multipath disturbance is largely dependent on the receiver’s environment since satellite signals can arrive at the receiver via multiple paths, due to reflections from nearby objects such as trees, buildings, vehicles, etc. Although the multipath effect can be reduced by choosing sites without multipath reflectors or by using choke-ring antennas to mitigate the reflected signal, it is difficult to eliminate all multipath effects from GPS observations. Since the geometry between the GPS satellites and a specific receiver-reflector location repeats every sidereal day, multipath tends to exhibit the same pattern between consecutive days. This repetition can then be useful for verifying the presence of multipath through the analysis of observations made at a static receiver on different days. In this study, the authors apply a wavelet decomposition technique to extract multipath from GPS observations. The extracted multipath signature is then applied directly to the GPS observations to correct for the multipath effects. The results show that the proposed method can be used to significantly mitigate the multipath effects at a permanent GPS station.

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2. Engineering survey work in the construction of floating docks
Petar Cerovac

The paper presents the engineering-surveying work carried out during the construction of floating docks in several parts on the berth and joining these parts on the water. These investigations were performed with regard to the construction of a steel three-pontoon floating dock with the possibility of self- docking; the obtained results have been applied during its construction.

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3. A fuzzy logic approach to the Ginzburg IV projection
O. Akyilmaz, T. Erden and C. Ipbuker

Ginzburg IV projection, which is also known as the CNIIGAiK 1939-1949 projection, is a modified polyconic projection that was preferred in the old USSR for mapping the whole world. There exist no mathematical equations which define the projection. In the Russian literature, the plane coordinates belonging to a given geographical latitude and longitude are given on tables in 10 degree interval. In this study, the fuzzy logic method is suggested for modelling geographical grids which are defined only with tabular coordinates, such as in the Ginzburg IV projection.

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4. Application of total station and laser correlation survey and depth measurement in an underground mine shaft
P P Bahuguna

The present paper describes a case-history of an application of modern surveying instruments in the correlation survey and depth measurement in a 400 m deep vertical underground mine shaft sunk from a depth of about 500 m to a depth of 900 m below the ground level. The technique presently used differs from other earlier techniques in that the depth is measured directly at various horizons in the shaft, from bottom to top, by using a total station.

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5. Decimetre level mapping using differential phase measurements of GPS handheld receivers
Ahmed El-Mowafy

An economic positioning system is presented in this study for decimetre level accuracy mapping with emphasis on producing base maps for GIS applications. The system downloads carrier-phase data of GPS handheld receivers online, simultaneously registers the point code and description, and processes the data in a differential post-mission mode. The architecture of the system is presented. Characteristics of the proposed system are discussed. Main issues in system utilization are investigated, including: treatment of system errors, phase measurements ambiguity resolution, the impact of receiver dynamics on system performance, and the required occupation time per point. Some guidelines for system operation are proposed. Several tests in the static and kinematic modes were carried out to test the performance of the proposed system. The system gave very promising results. Test results show that for a probability of 95%, an accuracy of less than 16 cm can be achieved after correctly resolving the ambiguities. With a cost that is a fraction of that of the currently used geodetic-grade GPS receivers, the system represents a cheap alternative for a wide range of GIS applications.

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6. Polynomial versus similarity transformations between GPS and Turkish reference systems
M Soycan

Efforts to utilize GPS have increased and come a long way in recent years. GPS (Global Positioning System) is the most modern and reliable technique for surveying geodetic control networks. By using relative static GPS observation, it is possible routinely to obtain sub-centimetre positional accuracy for points in geodetic control networks. GPS uses WGS84 (World Geodetic System 1984) as its reference frame. Point position on the earth is obtained by GPS observation in this frame. However, in geodetic and engineering applications, different coordinate systems are used as local or national systems. Combination of GPS networks with the national coordinate system requires determination of the transformation parameters between WGS84 (or ITRF) and the relevant national coordinate system. Several models can be used for transformation. The main purpose of this research is examination of 2 and 3D polynomial transformation models instead of 2 and 3D similarity transformations for distorted networks. However, the study also aims to determine reliable transformation parameters between ITRF94 and Turkish National Reference frame ED50 for Istanbul.

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7. Development of Singapore integrated multiple reference station network (SIMRSN) for precise fast static positioning

G. Hu, V. H. S. Khoo, P. C. Goh and C. L. Law

Fast and high precision GPS relative positioning is now increasingly used for many surveying applications on land and at sea. However, this technique requires the distance between the reference receiver and the user receiver to be within about 10km for high precision surveying work. Most users need to set up their own reference stations for DGPS measurements. This constraint will be removed by using a multiple reference station network. In order to use fast static centimetre-level positioning over larger distances, the Singapore Integrated Multiple Reference Station Network (SIMRSN) has been established in Singapore. The objective of this paper is to illustrate accuracy improvements in a fast static positioning mode using the corrected observations derived from within the SIMRSN network. After obtaining Test results are presented to demonstrate the improvement brought by the multiple reference station network approach.

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