Journal of Surveying Engineering

Resolving for integer phase ambiguities is an important issue of satellite surveying. In general ambiguity resolution techniques, observations made at tens of continuous epochs are required. These techniques usually fail in the case of cycle slip between global positioning system (GPS) satellites and GPS receivers happens intermittently. To overcome this, a novel technique, the single epoch kinematic (SEK) positioning technique, is proposed in this paper to resolve ambiguities based on observations made at only one epoch. In order to improve the computational efficiency, multiple wide lane ambiguities transformations and multiple statistic constraints are proposed and employed in this novel technique. Observations acquired from a $6\mathrm{km}\times 5\mathrm{km}$ test area with 25 check points are used for experiments. High accuracy of positioning and ratio of success for the experimental results guarantee the capability of the SEK positioning technique.

This paper describes the procedure for testing the statistical significance of point displacements in the geodetic network as the intermediate stage between the adjustment of respective epochs measurements and an in-depth deformation analysis. The cumulative distribution function of the test statistic, presenting the relation between the displacement and the displacement accuracy, is determined by simulations. On the basis of this cumulative distribution function a critical value of the test statistic for a selected significance level is determined. In the null hypothesis it is assumed that the point is stable. A comparison of the critical value to the test statistic value is made and the actual risk level for rejecting the null hypothesis is estimated. Further on, a practical example of implementing the test in a simulated network is given. The test statistic proved to be simple and applicable: The points with significant displacements were identified successfully.

Recently, the new Taiwan geodetic datum 1997 (TWD97) based on the Global Positioning System measurements has been established. Compared to the old geodetic datum, namely the Hu-Tzi-Shan datum, the TWD97 datum is more precisely defined. Since the TWD97 datum is a three-dimensional geocentric datum, while the Hu-Tzi-Shan datum is a locally defined horizontal datum and its triangulation points are deficient in the precise ellipsoidal height information, a three-dimensional coordinate transformation between both datums is therefore not appropriate. Moreover, there are the perceptible systematic errors in the triangulation networks in the Hu-Tzi-Shan datum. It is difficult to handle the systematic errors by ordinary datum transformation methods. In the paper, the technique of least-squares collocation is applied to the two-dimensional transformation from the Hu-Tzi-Shan datum to the TWD97 datum. By the present method, the systematic errors are predicted, and the coordinates of common points of both datums can be unchanged after the transformation. Our results show that the better transformation accuracy can be achieved by the least-squares collocation.

This paper is a summary of an experiment using Fresnel enantiomorphic diffraction in geodetic laser methods. In this study, results from the analysis of a large data set made possible the determination of the degree of accuracy of laser beam axes under various surveying conditions. An important part of the results is formed by the conclusions derived from the discussed method in specific geodetic applications, the advantages, as well as the disadvantages of the laser method, its comparison to conventional surveying methods, and an outline on further research.

In this paper we discuss a semiautomatic measuring system that can extract images of cracks in the surface of concrete from multitemporal images. An accuracy assessment and analysis of the relationship between expansion of the concrete and crack width are also included. The proposed scheme is comprised of four major components: (1) imaging geometry modeling for camera calibration; (2) initialization and skeletonization of cracks using the developed graphical user interface; (3) automatic crack tracing and width determination; and (4) multitemporal image processing and analysis. The experimental results indicate that the consistency of crack widths between the automatic extraction method and the manual measurement method could reach $0.05\mathrm{mm}$ or better.

This paper presents a methodology used to assess and select areas for landfills implantation in the city of Cachoeiro de Itapemirim–ES (Espírito Santo State), Brazil, using multicriteria analysis and geographical information systems (GIS). Fifteen areas between 20 and $200\mathrm{ha}$ were found that presented suitability greater than 220 (score limit). The present landfill is in an area with null suitability (the worst possible) and distant from the areas with suitability over 220. The results showed that GIS was a useful and agile tool in integrating spatial information for decision making in the assessment and selection process of areas suitable for landfill implantation.

Time aloft and distance traveled in free flight with a paraglider are determined by three factors: weather conditions, pilot skill, and paraglider performance. The latter factor can be represented in a performance curve. To construct an accurate performance curve, a surveying engineering approach was applied. Sensors (a variometer and a wind speed indicator) were first calibrated by Global Positioning System receivers. A test flight was then carried out with a paraglider which was launched to an altitude of $750\mathrm{m}$ using a stationary winch. After release, the variometer and wind speed indicator logged vertical velocity and horizontal velocity, respectively, for different angles of attack of the paraglider airfoil. This data, corrected for atmospheric conditions, was analyzed, via least-squares adjustment mathematical models, to determine an accurate performance curve.