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Vol. 40, No. 309. July 2008 1. Test of simulated pseudolite measurements applied to GPS and multi-pseudolite integrated positioning C. C. Chang, P. C. Lou and P. J. Ke The near-ground operation of a GPS-like signal transmitter, the pseudolite (PL), is expected to provide extra-measurements and improve the GPS positioning accuracy and availability. Based on the true measurements received from one PL instrument during the field trial, the multi-session combined technique and the self-session duplicated technique were proposed and tested for PL data simulation. The results demonstrate that the self-session duplicated technique can effectively provide the simulated PL measurements for any appropriate number and adequate configuration of so-called virtual PL (VPL) sites. The GPS+PL+3VPL observations were practically integrated to compute for a baseline solution. The results prove that baseline precision can be significantly improved by approximately 50% and 30% on the horizontal and vertical components, respectively, compared with those using only GPS data. When VPL sites are simulated to have the minus elevation angles, the vertical positioning errors can be further reduced to achieve a consistent precision in all three-dimensional coordinates. This preliminary study has shown good performance of using simulated PL measurements for integrated GPS and multi-pseudolite positioning.
F. Döner and T. Yomralioglu Scientific studies associated with land require large amount of data. The data is often collected during field studies with the use of pencil and paper based method. The method is labour-intensive and susceptible to recording and georeferencing errors during transcription. Recent advances in mobile computing, positioning and software now make it possible to bring field and office activities into a collaborative environment, thereby minimizing human errors and time delays. This paper assesses the use of Mobile Geographic Information Systems (MGIS) as an appropriate tool for geo-data acquisition applications. Firstly the computing, positioning, software and communication technology behind the system is presented. A Mobile Geographic Information System developed for field data acquisition based on the combination of Geographic Information Systems (GIS) and Global Positioning System (GPS) is described. Finally, the system is tested in two field studies to examine its effectiveness compared to traditional methods in terms of accuracy, cost and project completion time. The field studies demonstrate the noticeable gains in efficiency and cost saving achieved with the use of the MGIS technology. Results of the field studies verify that MGIS is very useful for georeferenced data acquisition applications.
M. Vulic and D. Blagojevic The historical levelling data of the epoch of 1950-1960 were used along with the levelling data of the epoch of 1970-1973 for the derivation of the vertical velocity field on the territory of the Republic of Serbia. The methodology was based on the construction of a kinematic network and least squares adjustment and aimed at obtaining the vertical velocities of representative benchmarks. Being the first attempt of this kind for the area under investigation, no further interpretation of the result is given, apart from a couple of remarks concerning the correlation between the gradient surface and the general geophysical features.
D. D. Lichti and J. Lampard A method for reflectorless total station self-calibration of face left and face right observations in a network is proposed. The mathematical models for the observation equations augmented with systematic error terms are presented. The method is demonstrated on three datasets captured with two reflectorless total station instruments: a Trimble 5603 DR200+ and a Leica TCRA 1103+. The results show improvement of up to 71% in the RMS of estimated residuals as a result of self-calibration. Furthermore, most of the error model parameters can be estimated with sub-millimetre or sub-second precision. Statistically significant differences between some calibration parameters from two Leica datasets were found, but closer analysis shows that these are of no metric consequence. Incidence angle is demonstrated to be a significant factor in distance precision, as has been reported elsewhere for terrestrial laser scanners. Comparison of the results with those from independent component testing shows that the self-calibration method is superior for determining angular error parameters. A close agreement of 1.1 mm was achieved between the additive constant estimates from self-calibration and baseline calibration methods for the Leica instrument. The additive constant estimates for the Trimble instrument differed considerably, which is likely due to the observed non-linear behaviour of the distance meter at close range.
Yuanxi Yang and Xianqiang Cui An adaptively robust filter with multi adaptive factors is proposed, based on the principles of adaptive Kalman filter and bifactor robust estimation for correlated observations. The estimator of the adaptive filter with multi adaptive factors is derived. The corresponding adaptive factors for the components of the position vector and velocity vector are set up based on the discrepancy of the predicted state from the kinematic model and the estimated state from the measurements. The adaptively robust filter with multi adaptive factors is more flexible in controlling the disturbing effects of the state components compared to the adaptively robust filters with unified adaptive factor and classified adaptive factors. The existing problems of the adaptive filter with multi adaptive factors are analyzed. An actual GPS dada set of an aircraft is calculated and analyzed with four schemes. It is shown by the actual calculation that the results of the adaptive filter with multi adaptive factors are slightly superior to those of the adaptive filter with unified adaptive factor. However, the new adaptively robust filter cannot be applied when the number of measurements at some epochs is smaller than the number of state parameters. It is proposed that the adaptively robust filter with multi adaptive factors and that with unified adaptive factor could be integrated in practical applications.
H. Nahavandchi and A. Soltanpour A limiting factor for successful ambiguity resolution in precise GPS positioning is the existence of un-modelled ionospheric errors in both the carrier phase and the pseudorange measurements. In this study, the ionospheric delay is modelled using a four-parameter polynomial utilizing dual frequency observations in the region of study in southern Iran. Thereafter, the corrected and non-corrected observations for ionospheric delay are compared with the ionospheric-free solution of the same observations. Two baselines (15 km and 72 km) are used for this comparison. An improvement of 0.22 ppm and 0.07 ppm is achieved, respectively, for the two baselines. Further, the ionospheric delay is modelled using two other methods, i.e. the Klobuchar and divergence models. The divergence model uses single frequency observations. The improvement of the results is restricted as the noise level in code observations is high. An improvement of 0.15 ppm for the 72 km baseline and no improvement for the 15 km baseline are observed using the divergence model. The Klobuchar model corrects 50%-60% of the ionospheric errors in this study.
A. L. Johnson Height differences are now seldom measured by observing “Reciprocal Vertical Angles”, and the method is generally considered to have been superseded by digital levels and GPS. This paper argues that the technique may still have an important part to play in verifying the results obtained from GPS, and is also considerably more accurate than may generally be supposed. 8. Determination of optimum residual gravity anomalies for mineral exploration: a least squares collocation approach T. O. Idowu, P. C. Nwilo, F. A. Fajemirokun and C. U. Ezeigbo Analysis of gravity anomalies, measured on the earth’s surface, can reveal information on sub-surface structures of the earth. The first step in this analysis is to extract residual gravity anomalies (needed for mineral exploration) from the observed gravity anomalies. Currently, a classical least squares technique is used to achieve this aim. However, this technique does not produce optimum results because it assumes that the observed gravity anomalies used for the computation of residual gravity anomalies are error free, whereas, all observed quantities are affected by random errors. In this study, an attempt was made to extract the residual gravity anomalies from the observed gravity anomalies using a least squares collocation technique. The least squares collocation technique was considered to be a better alternative because its formulation takes the presence of random errors of observations in the observed quantities into consideration and makes provision for filtering out the errors from the observed quantities while predicting the needed signals at the required number of points.
C. Ïnal, Ï.Sanlioglu, C.Ö.Yigit The calibration values of electromagnetic distance measurements, which have been given by their own firms, can lose their currency in time. So, the EDMs must be controlled in the particular time intervals. The EDM controls have been usually made in the EDM calibration baselines, which are constituted for this aim. Zero addition, scale coefficient and phase difference measurement function constitute the measurement function as a result of control done. The EDM calibration baseline must be scaled to determine the scale coefficient. Not only high accuracy instruments as Kern Mekometer 3000 but also GPS can be used for scaling. In this study, it has been investigated that possibility of scaling of EDM calibration baseline by using GPS and the scaled EDM calibration baseline, and the calibration parameters of Sokkisha SET2, Topcon GTS701, Topcon GTS 229 and Sokkia Power SET 2000 electronic tacheometers have also been estimated.
1. Mapping impervious surface areas from GIS planimetric
data 2. Land tenure reform in Uganda some reflections on the
formalization of customary tenure The paper provides an overview of the history of land tenure reform
in Uganda from 1900 to 2000. Methods, which were used to formalise
customary tenure in Uganda, are reviewed and the effects of the
first reform, which formalised customary tenure through negotiations
with local leaders are reported. The subsequent reform in which
the colonial administration, relying on the power of the law, formalised
customary land into freehold and leasehold without any consultations
with the local population, is described. The land distribution policy
enshrined in the Crown Lands (Adjudication) Rules, 1958 is related;
the reactions of the indigenous people to the reforms in Uganda
are highlighted; and the contribution of the independent Uganda
government in the land tenure reform is discussed. The study concludes
that both the negotiated and the enforced non-negotiated approaches
successfully formalised customary tenure and that the negotiated
approach was much better and preferable within the African context.
It further concludes that the theory purporting that the indigenous
people were incapable of adapting to the western forms of individual
ownership was a political gimmick aimed at supporting and justifying
the mandatory acquisition and formalisation of customary land for
exclusive use of non-Africans. Finally the study proposes criteria,
which should be followed by any country wanting to formalise customary
land. 3. On zero position correction of hanging tape of gyro-theodolite Detailed theoretical analysis of the working characteristics of the hanging tape torque and the computation of zero position correction in the orientation observation with the gyro-theodolite are made in the paper. The practical data prove that the conclusion is right. 4. Re-alignment of a guyed tower Towers are typical structures that can be found in many urban and rural landscapes the world over. From their basic design, they are usually exposed to severe environmental loads. It is therefore prudent to carry out periodic maintenance that includes checking that they are correctly aligned. This paper describes a method that was used for the re-alignment of a guyed tower in Limuru, Kenya. Angular and distance observations, made from two observation points detected a vertical misalignment that was larger than the acceptable tolerance of An iterative re-alignment procedure was then applied, resulting in an acceptable final misalignment of 5. Transformation of 3D GPS Cartesian coordinates to ED50
using polynomial fitting by robust re-weighting technique. The purpose of this study is the solution of transformation problem between the GPS networks and old geodetic networks based on the national coordinate system alternatively by a 3-dimensional robust polynomial transformation (3D.R.P.T). This study focuses on and probes 3D similarity (3D.S.T), 3D polynomial transformation with least squares estimate as equal-weighted (L.S.3D.P.T), 3D polynomial transformation based on weight with the inverse of the distances of common points to the center of gravity (W.L.S.3D.P.T) and robust estimate approaches that are re-weighted and are based on iterative solution. Detailed mathematical model and solution algorithm of the proposed model is given, and it has been applied in a test area covering the city borders of Istanbul for which its results were studied and compared to other three methods.
An algorithm is derived to transform Cartesian coordinates to geodetic
coordinates by employing ellipsoidal coordinates in an intermediate
step. The algorithm is comparatively simple and stable in all steps
for any point in space outside a geocentric sphere of an approximate
radius of 43 km. 7. Astronomical azimuth determination by the hour angle
of Polaris using ordinary total stations The determination of the astronomical azimuth of a line is not
a difficult task for surveyors any more. The aim of this paper is
to analyze the theoretical details and errors in order to propose
the use of ordinary total stations, for an easy, efficient and accurate
determination of the astronomical azimuth of a line by the hour
angle method via Polaris sightings. As many modern total stations
have a built – in quartz clock they can register automatically
the UTC time as well as the angle measurements (horizontal and zenith)
of each observation. The total fieldwork time needed is about 10
minutes and the accuracy that may be achieved is about +/- 2 arc
seconds. This procedure will be proven to be easier than the determination
of the geodetic azimuth of the same line. The calculation is independent
and the result is free of the errors that the coordinates of a survey
mark may contain, because they are not used. However good positional
data is required from other sources. Astronomical azimuths are an
alternative solution for the surveyors in order to check or orient
their field surveys and arbitrary networks independent of the GPS
system. 8. The effect of different tropospheric models on precise
point positioning in kinematic mode Precise Point Positioning, based on undifferenced dual frequency
GPS carrier phase observations, is a relatively new data processing
technique for high accuracy kinematic GPS applications. No reference
station data is necessary making the technique applicable e.g. for
airborne high accuracy GPS positioning in remote areas where the
distance to the nearest GPS reference station otherwise would be
hundreds of km. High accuracy kinematic GPS positioning is used,
for instance, for airborne remote sensing with gravimetry, In SAR,
or lidar equipment, where data is collected for various geophysical
applications. In the remote areas of Greenland, Northern Canada
and the Northern parts of Scandinavia airborne remote sensing is
carried out by various professional groups every summer, and most
of these groups would like improved and more reliable high accuracy
GPS positioning algorithms. 9. Comparing stochastic models used in GPS precise point
positioning technique GPS observables are normally processed using the least-squares
method. In order to ensure high accuracy positioning results, both
the functional model and the stochastic model must be correctly
defined. In GPS Precise Point Positioning (PPP) mode, an ionosphere-free
linear combination is generally used for constructing the functional
mode, while post-mission information and error mitigation methods
are employed to eliminate many biases. Nevertheless, some unmodelled
biases still remain in the GPS observables and eventually cause
errors in the coordinate results. It is, however, possible to further
improve the accuracy and reliability of GPS results through an enhancement
of the stochastic model. This research aims to investigate stochastic
models used in the GPS PPP technique. Three different stochastic
models; equal weight for all GPS observables, different weight for
each GPS observable based on satellite elevation angle and different
weight for each GPS observable based on the MINQUE (Minimum Norm
Quadratic Unbiased Estimation) procedure, have been compared in
this paper. Test results indicate that the stochastic model estimated
from the MINQUE method produces the most accurate coordinate results
both in horizontal and vertical components. 10. Precise height determination using simultaneous-reciprocal
trigonometric levelling Precise levelling method has been used for the determination of
precise height for many years. The application of this technique
is difficult, time consuming and expensive especially in rough terrains.
These difficulties have forced researchers to examine alternative
methods of height determination.
Vol. 40, No. 307. January 2008 1. Height Transformation using regional geoids and GPS/levelling
in Turkey Transformation of ellipsoidal heights derived from the Global Positioning System (GPS) to orthometric heights using geoid models is investigated in the north and west parts of Turkey. Although the transformation depends on a simple relation between ellipsoidal h, orthometric H and geoid N heights, the accuracy of the resulting orthometric heights after transformation is crucial in geodetic and surveying applications. Various factors which affect this accuracy, such as measurement errors, datum inconsistencies and theoretical assumptions, are investigated in this study, while testing different methods in three test networks (Sakarya in the Northwest, Çankiri in the North and Izmir in the West). The study consists of three steps. In the first step the regional Turkey geoids TG99A, TG03 and the European gravimetric geoid EGG97 are tested comparing geoid heights derived from models and GPS/levelling at co?located benchmarks. In the second step, regional geoid models are combined with GPS/levelling using Least Squares Adjustment of height differences and corrector surface models. In this step, additionally, Variance Component Estimation (VCE) using Minimum Norm Quadratic Unbiased Estimation (MINQUE) approach is performed, in order to combine the height sets. In the last step, GPS/levelling surface type local geoids are determined and their performances are tested in transformation of GPS?heights. Finally, the resulting accuracies are compared and practical aspects of those approaches in deriving orthometric heights from GPS measurements in geodetic and surveying applications are discussed. KEYWORDS: Ellipsoidal heights. Geoid EGG97. Geoid models. MINQUE, Variance Component Estimation. 2. Verification of accuracy of precipitable water vapour
from GPS during typhoon Rusa This paper presents GPS meteorology using GPS observations obtained from the Korean permanent GPS network during a severe weather condition. Our first experimental studies in Korea were based on data collected from seventeen GPS stations and four radiosonde stations during the period of Typhoon Rusa from 31 August to 1 September 2002. The root mean square difference (RMSD) between the GPS Precipitable Water Vapour (PWV) and the radiosonde-PWV was at the 7.2 mm level. In this new study, a least square analysis was used to reduce the large RMSD and without bias, the RMSD was reduced to 5.7mm. The mean of the RMSD without consideration of Typhoon Rusa effect was 6.9 mm, whereas the RMSD of GPS-PWV with consideration of the Rusa effect was worse with 9.4 mm. The large RMSD during Typhoon Rusa was due to the change of the observation direction of the balloon based radiosonde by high wind speeds. KEYWORDS: Precipitable water vapor, GPS, Radiosonde, Typhoon Rusa
The drive for sustainable development has led governments to create new interests over land. The role of cadastral and registration systems in the mapping and management of these new interests is unclear. Whilst these systems have always played an important role in the administration of land parcels and ownership, the new land interests are increasingly being mapped and managed elsewhere. As a result administrative inefficiencies and transaction complexities are growing. Existing cadastral and registration systems have the capacity to improve the situation; however, a guiding framework for their inclusion is needed. This paper introduces a framework of principles that articulate the roles of cadastres and registration systems in the management of new land interests. Importantly the framework is holistic and reflects other components essential to good land administration. These include the roles of land policy, legislation, flexible tenures, institutions, spatial data infrastructures and capacity building. The principles will systematize the management of land interests across different jurisdictions. KEYWORDS: Cadastral Surveying. Land Administration. Land Interests. Property Rights. 5. Turkish cadastral system In Turkey, cadastral works were started after the foundation of the Republic of Turkey. These studies were carried out in such manner that ownership of the land was given to the people who were using it. Firstly, in 1924, the process was started in urban areas where one fourth of the total population of the country lived. Because of various problems including economic difficulties, technical deficiencies, personal insufficiencies, these cadastral works were only carried out in cities within the first 25 years from 1925 to 1950. Then the cadastral works were speeded up and most were carried out between 1950 and 1990. In this period, the work was achieved utilizing the available technology at that time in rural and urban areas. Today, 97% of the urban cadastral areas and 67% of the rural cadastral areas have been completed in Turkey. Generally, graphic, photogrammetric, orthogonal, and tachometric measurement methods have been used in this work. While 45% of the Turkish cadastral maps have been produced using graphic method which does not have a coordinate system, the other maps have been produced using the different measurement methods. These are also in different coordinate systems and scales. Only 7% of the whole cadastral maps are in digital format. On the other hand, because of the factors mentioned above, Turkish cadastral bases do not contain sufficient information to be converted to digital system in accordance with field. Since 1990, different methods have been used to digitize these non-digital cadastral maps. However, these attempts have failed. The main goals of this study are identifying historical background of cadastre and existing situation of its in Turkey. KEYWORDS: Cadastral survey. Turkey. Digitisation. Land ownership. 6. A Review of surveying methods for sports and leisure Applications of modern geodetic instruments in sports and leisure-related activities are reviewed in this article. Total stations, satellite GPS receivers and laser leveling systems are used to standardize dimensions of sporting grounds, to accurately and digitally record performances in jumps and throws during games, to boost performances of athletes in rowing by recording the details of the vessel kinematics during training, to navigate yachts, boats and mountaineers, and to define heights of high-flying kites. KEYWORDS: Sport. Electronic instruments. Sport measure recording. Track lengths. 7. Stable point research on deformation networks Determination of the deformation of a geodetic network is an objective of the analysis of various geodetic deformation measurements. Deformation analysis is a step by step procedure, which in general begins with a global congruency test. If the coordinates of repeated measurement campaigns with its variance-covariance matrices and their datum are available, the question arises if congruency between different epochs exists. The analysis of the deformation field was performed in three dimensions. An alternative test procedure for detection of unstable points within the block assumed as stable beside the conventional method for congruency investigations is proposed and for both methods example solutions are given. The procedure is based on Similarity transformation. The benefit of both methods are discussed. KEYWORDS: Similarity transformation. Deformation. Geodetic network. Unstable points. 8. Using the virtual reference stations (VRS) concept for
long-range airborne GPS kinematic positioning In this paper, the potential of long-range kinematic GPS positioning with a multiple reference station (MRS) network for airborne applications is discussed. A novel method of creating Virtual Reference Stations (VRS) is proposed for post-processed airborne GPS kinematic applications, which is called the modified semi-kinematic VRS method (MS-VRS). The purpose of the VRS is to generate data from real GPS observations made by the MRS network, resembling that of a non-existing (virtual) reference station situated close to the project area, so that the commonly used methods for short-range kinematic GPS data processing can be used to determine the position of the aircraft. During the initial phase, the VRS of the MS-VRS method refers to a fixed position according to the aircraft’s initial approximate position, and the corrections are applied according to the aircraft’s trajectory. The MS-VRS method differs from the conventional VRS method and semi-kinematic VRS method (S-VRS) in that when the aircraft’s current approximate position is more than 10 km from the initial VRS position, a new VRS is created. The MS-VRS data can be generated in RINEX format, so that it can be processed using any kinematic GPS post-processing software. Using a simulated kinematic test with static data, the MS-VRS method showed a 12.1 to 47.6 percent improvement in the three coordinate components with respect to the conventional single reference station (SRS) approach. Tests and analysis with real airborne GPS data are presented in some detail using a MRS network and flight test data in Norway. The results indicate that centimetre-level accuracy can be achieved based on the proposed MS-VRS method, which is superior to the S-VRS method, with improvements of 11.4 to 47.4 percent in terms of standard deviations of the coordinate domain. KEYWORDS. Long Range Airborne GPS. Kinematic Positioning. Virtual Reference Stations. 9. Proposal for developing the Syrian stereographic projection The conformal stereographic projection adopted
by the Syrian survey authorities to represent the geodetic positions
was designed for an age of paper maps according to geographical
characteristics of Syria in the French mandate time (1920), which
includes only the effective and cultural part of the country. Nowadays,
this situation has changed since projects of land reclamation and
of exploring petroleum in Al Gazira have been launched as well as
modern surveying techniques such as Global Positioning System (GPS)
and Geographic Information Systems (GIS) have been applied. This
paper aims at overcoming the defects in the Syrian stereographic
projection of the whole country by suggesting a new calculation
approach and minimizing the errors in linear scale.
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