Integrating GPS with national networks by collocation method

The concepts of coordinate systems required to identify points in space and represent them on maps uses mathematical methods of assigning numbers, called coordinates to each point in space. There are different coordinate systems the commonest being the system of latitudes, longitudes and ellipsoidal heights. The situation is complicated because the latitudes and longitudes of the same point differ slightly depending on the geodetic coordinate system of a country, the result being that different systems of latitude and longitude in use for the same point can disagree in coordinates by more than 200 metres. The GPS for instance uses a WGS84 system and gives latitude and longitude values which can not be integrated directly into the mapping system of a country without suitable mathematical conversions. Similarly, it is not possible to just measure distances from a graticule map without appropriate projection conversions. In order to use data obtained from GPS measurements correctly and effectively in Ghana, we need to use appropriate transformation parameters that relate our Ghana National Survey Mapping coordinate system to that used for the Global Positioning System (GPS). Datum transformation parameters define functional relationship between two reference frames. This paper looked at geodetic coordinate systems and transformations between the WGS84 and the coordinate systems used in Ghana (the Ghana war office system and also the Clarke1880 system) using the Bursa-Wolf model. Particular attention was given to the derivation of ellipsoidal heights through the use of the Abridged Molodensky formulas. Keywords: Coordinate Systems, ellipsoidal heights, Global positioning System, WGS84, Transformation parameters Journal of Science and Technology Vol. 28 (1) 2008 pp. 116-127

The present theory of the determination of the position of an Earth satellite from simultaneous measurements of the topocentric coordinates at 2 or more geodetic satellite points is not exact. The inaccuracy is caused by the fact that the measured topocentric coordinates of the satellite are defined in a system in which the directions of the axes are not exactly parallel to the directions of the corresponding axes of the geodetic system in which the coordinates of the satellite points are given; this difference in direction is not respected in the solution. The paper gives an exact solution of the problem. The concepts (4) of geodetic topocentric declination and geodetic hour angle of the satellite, i.e. the declination and hour angle in the geodetic reference system, are introduced. With these quantities the problem of determining the position of the satellite is then solved exactly. There always exist superabundant observations so that the method of least squares can be used. The procedure is outlined for the case of conditioned observations (suitable for 2 satellite geodetic points) and for the case of intermediate observations (suitable for >2 satellite geodetic points).

As a new method for power line inspection, unmanned aerial vehicle (UAV)-based inspection is efficient and low-cost. Since the flight speed of UAV is fast, target auto-tracking and photographing of the airborne equipments including visual-light camera, infrared thermal imager and ultraviolet imager, is a very important and useful function. In this work, a power line inspection system suitable for UAV-based inspection is built, and based on this system, an auto-tracking algorithm used for UAV power line inspection is proposed. Theories including coordinate transformation of three coordinate systems (geodetic coordinate system, geocentric rectangular coordinate system and NEU coordinate system) and spherical approximation method of treating arc length as chord length are applied to this auto-tracking algorithm. Through this algorithm, airborne cameras' shooting angle can be automatically modified to keep tracking and photographing power line during the inspection, using the real-time captured GPS data of UAV. The requirements on GPS positioning accuracy for the algorithm are also discussed in this work.

Referring to the possible problem of gyro random drift effect on the Line of Sight (LOS) stabilization accuracy, a method for the LOS stabilization based on visual attitude estimation is proposed. A monocular vision system is established by four coplanar reference points on the ground and a double-focus CCD camera in the carrier. The quaternion is used to represent the transform relation between geodetic coordinate system and carrier coordinate system, and the square-root unscented Kalman filter in which the current statistical model is applied to obtain the system state equations is used to estimate the attitude parameters. On this basis, the velocity interference model of the LOS is derived according to coordinate transformation and rigid body kinematics, and the method of feedforward control is adapted to isolate the influence of the LOS velocity disturbance. The simulation results indicate that the proposed method is effective in stabilizing the LOS without changing the structure of the tracking units.

The track fluctuation of helicopter pod used for magnetic survey can cause interference with magnetic field measurement results. By simulating the small fluctuation of inclination angle and drift angle,the pod track fluctuation in airborne coordinate system and the helicopter track fluctuation in geodetic coordinate system are analyzed in detail, and the track fluctuation model is established and calculated in a simulated environment. Results indicate the magnetic interference rules of the track fluctuation, and can provide a theoretical support for magnetic interference compensation.

Until the advent of satellite positioning and navigation systems, and in particular the Global Positioning System (GPS), geodetic coordinate systems were of little interest to many surveyors or navigators. Indeed, many of today's problems and difficulties stem from this historical misunderstanding of the true complexity of systems of coordinates. This paper will briefly describe a number of common types of coordinate representation and common coordinate systems and datums. In order to relate coordinates based on differing systems it is also necessary to understand the methods of transforming coordinates from one system to another. The methods of transforming geodetic coordinates are discussed in the second part of this paper.

Integrated TLS and GPR data can provide multisensor and multiscale spatial data for the comprehensive identification and analysis of surficial and subsurface information, but a reliable systematic methodology associated with data integration of TLS and GPR is still scarce. The aim of this research is to develop a methodology for the data integration of TLS and GPR for detailed, three-dimensional (3D) virtual reconstruction. GPR data and high-precision geographical coordinates at the centimeter level were simultaneously gathered using the GPR system and the Global Navigation Satellite System (GNSS) signal receiver. A time synchronization algorithm was proposed to combine each trace of the GPR data with its position information. In view of the improved propagation model of electromagnetic waves, the GPR data were transformed into dense point clouds in the geodetic coordinate system. Finally, the TLS-based and GPR-derived point clouds were merged into a single point cloud dataset using coordinate transformation. In addition, TLS and GPR (250 MHz and 500 MHz antenna) surveys were conducted in the Litang fault to assess the feasibility and overall accuracy of the proposed methodology. The 3D realistic surface and subsurface geometry of the fault scarp were displayed using the integration data of TLS and GPR. A total of 40 common points between the TLS-based and GPR-derived point clouds were implemented to assess the data fusion accuracy. The difference values in the x and y directions were relatively stable within 2 cm, while the difference values in the z direction had an abrupt fluctuation and the maximum values could be up to 5 cm. The standard deviations (STD) of the common points between the TLS-based and GPR-derived point clouds were 0.9 cm, 0.8 cm, and 2.9 cm. Based on the difference values and the STD in the x, y, and z directions, the field experimental results demonstrate that the GPR-derived point clouds exhibit good consistency with the TLS-based point clouds. Furthermore, this study offers a good future prospect for the integration method of TLS and GPR for comprehensive interpretation and analysis of the surficial and subsurface information in many fields, such as archaeology, urban infrastructure detection, geological investigation, and other fields.

Locations on and around planet Earth are commonly represented in a geodetic coordinate system with a longitude, a latitude, and a height.Longitude is the "horizontal" dimension with a domain from -180to 180, which spans the entire 360circumference of the planet.Where the two domain bounds meet is known as the 180th meridian or the antimeridian.

A three‐dimensional (3‐D) model based on the connectivity of astronomic and geodetic coordinate systems is developed from basic principles. It provides for simultaneous adjustment of most conventional types of terrestrial surveying observations. Observation equations express observed quantities in 3‐D space and are referenced to the local vertical at the point of observation. Classical reductions of observations to the reference ellipsoid prior to adjustment are not necessary. A least squares solution yields adjusted geodetic rectangular coordinates from which geodetic latitude, longitude and height values may be found. For most networks, astronomic coordinate values will also be obtained, but these values are probably reliable only if astronomic observations are included in the survey. The 3‐D model should provide a sound theoretical basis for development of a fully‐integrated adjustment model that includes conventional, photogrammetric, inertial, satellite and other surveying system observations. Additional research is desirable to evaluate the 3‐D method's full potential for applications such as local densification and project control surveys.

This document reports on the organization and conduction of a series of roundtables held in Kyiv and Lviv, both offline and online, dedicated to the implementation of a new high-precision geodetic reference coordinate system, UGS 2000, in Ukraine. The discussions covered the current status and development paths of the national geodetic reference system, as well as issues related to the development of the state leveling and gravimetric networks of Ukraine.

This paper reviews the fundamental definitions of geodetic and geocentric coordinate systems, whilst clarifying the distinction between coordinates and coordinate systems. It is then argued that the transformation of coordinates from a local geodetic datum to a geocentric datum should first employ a change of the coordinate system using a six- or four-parameter transformation, followed by further modeling of the distortion in the coordinates. It is also argued that the horizontal coordinate transformation should not include height information, since this forms an entirely different coordinate in another coordinate system.

Prior to the advent of satellite positioning, geodetic systems were based on a mathematic model of the Earth which best fits over a specific area. The surveys were developed for mapping requirements where precision of a meter was considered satisfactory. With the adaptation of space positioning techniques by the scientific community, the geodetic systems assumed a global character where centimetric precision could be obtained by these systems. As a consequence of the new technologies, the change from local datum to geocentric reference systems is required, in order to make the information compatible on an international level. To this end Brazil has been involved in the definition of the South American Geocentric Reference System (SIRGAS), whose purpose is to establish a geodetic system for the whole of South America. Brazil will complete the next step to accomplish this change.

In July 2000, Hanoi-72 reference system was replaced by the Vietnam reference system, namely as VN-2000 as an official geodetic background system in Vietnam. Ministry of Natural Resources and Environment of Vietnam has reported the transformation parameters between VN-2000 and WGS84. Nevertheless, there is a need to estimate a new transformation parameter set between VN-2000 and WGS84 because WGS84 has been updated. In addition, there is now a lack of an accurate published set of parameters for transformation from VN-2000 to not only the International Terrestrial Reference System ITRS but also PZ-90. In this study, coordinate transformation parameters between ITRS and VN-2000 are estimated through the use of a least square approach and the common points with known coordinates in both systems. These set of parameters was then deployed to determine the link between VN-2000 and WGS84 as well as PZ-90. The results denoted that the derived transformation parameters, on the basis of the results at the checkpoints, could generated station positions with the accuracy at several cm level for transformation from VN-2000 to the new realizations of ITRS, WGS84 and PZ90 and reversely. These achievements reveals that the set of parameters is great significance for many applications related to positioning in Vietnam.

A collocation method with space–time radial polynomials for inverse heat conduction problems

A generalized weighted total least squares-based, iterative solution to the estimation of 3D similarity transformation parameters