Journal of Surveying Engineering

Real-time determination of orthometric heights at cm level accuracy can be achieved in Dubai, U.A.E., using a single geodetic-grade global positioning satellite (GPS) receiver. This process requires that the rover receiver uses on-line measurement corrections from multiple reference stations real-time kinematic (RTK) networks, and geoid heights from a precise gravimetric geoid model. The Dubai RTK network consists of five active reference stations and can provide ellipsoidal heights with external accuracy less than 4 cm and a precision of 3 cm. The Dubai geoid model was recently developed integrating a comprehensive set of gravity, GPS, leveling, and digital elevation data to fit GPS/leveling at the 3–5 cm level RMS. To evaluate this technique, a field test on 41 benchmarks of the Dubai second-order leveling network was performed. In this test, orthometric heights derived from the presented method using a single GPS receiver were compared to their precise values determined by spirit leveling. The height differences were analyzed and statistically examined. Results show that orthometric heights determined from the GPS RTK network and geoid data can be accurate to 2–5 cm with no significant systematic errors. The method can thus be considered a good alternative to traditional leveling, particularly for third-order leveling in large areas.

In terms of computer algebra systems, an inverse problem of a meridian arc is discussed in two somewhat different ways in this paper. One is the conventional power series method and the other is a Hermite interpolation. The research in the paper shows that the derived new solutions are concise in form and high in accuracy. The paper also shows that a computer algebra system is a powerful tool to solve some mathematical derivations in geodesy, surveying, and cartography.

In practice, the coordinates necessary in geometric rectification are usually derived from medium scale maps such as $1:\mathrm{50,000}$ or $1:\mathrm{25,000}$ scale topographic maps. However, the total positional error of any point on these maps may exceed 1.0 mm due to pointing uncertainty, position shift, and exaggeration from cartographic generalization, paper shrinkage, etc. As spatial resolution of satellite imagery such as Landsat 7 panchromatic, ASTER VNIR, Spot 5 are now in the range of 5–15 m, ground control point (GCP) coordinates derived from medium scale maps are no longer acceptable since the magnitude of positional error may be up to several pixels. Larger scale maps may be used, but their coverage is limited to urban and high-density areas. This problem may be alleviated by adopting differential global positioning system (DGPS) techniques which can provide coordinates of up to 1 m accuracy. However, the technique is effective only for short baselines because the unmodeled errors are directly proportional to the baseline length. The need for at least two GPS receivers to operate simultaneously during data acquisition renders the technique less than desirable for most remote sensing applications. Developing a GPS technique that not only requires the operation of a single GPS receiver, but also provides accurate positioning results suitable for GCP establishment of medium and high resolution satellite imagery is the focus of this research. Interest in single receiver positioning has been rekindled by the recent availability of postmission satellite clock and ephemeris information generated by various data analysis centers, as byproducts of the data processing carried out under the auspices of the International GPS Service. This paper describes how postmission information and advanced data processing techniques are introduced into the precise point positioning software to improve the positioning accuracy. The results presented in this paper clearly demonstrate that an accuracy of better than 1 m in horizontal components can be achieved over a 15 min observation period using a dual-frequency GPS receiver.

A long-range geoid testing procedure is presented using a geometrical geoid profile, which extends in an approximate north–south direction between the Mediterranean and the Black Sea. Along the first-order leveling line of the Turkish National Vertical Control Network (TNVCN), 47 leveling benchmarks at $20–25\mathrm{km}$ intervals were selected as global positioning satellite (GPS)-leveling control points with known Helmert orthometric heights. The geometrical geoid profile computed from GPS-leveling data was compared with the national Turkish Geoids 1991 (TG91) and 1999A (TG99A), and global geoids OSU91A and EGM96. In absolute geoid testing, it is verified that TG91 has a tilt and bias with respect to the GPS-leveling geoid. TG99A, which has no tilt and bias, displays the root mean square agreement of $\pm 12\mathrm{cm}$ in the north–south direction. In relative geoid testing, it is understood that TG91 can only be used at $25\mathrm{km}$ or shorter baseline lengths, whereas TG99A can be used over all baseline lengths with an accuracy that is equal to the tolerance value for the second-order leveling control.

One of the possible uses of the global positioning satellite permanent stations is to use them as a datum reference when a new base station is established in a geodetic or surveying project. However, the actual procedure is not always obvious. Combining a number of permanent stations in the process involves important decisions that the analyst must make, which can alternate the results dramatically. Important network design aspects that must be addressed are, for example, how many permanent stations should be involved in the process; how long should the session duration be; how should one constrain the permanent stations in the adjustment procedure; and so forth. This paper suggests an algorithm based on multibaseline processing, minimum constraints, and free net adjustment concepts, in order to produce a base station with reliable coordinates and realistic accuracy, while using one or more permanent stations. In order to demonstrate the algorithm and to support the conclusions, it presents numerical examples from the Permanent Stations Array in the State of Israel, processed at the Technion—Israel Institute of Technology, using GAMIT software.

In this study, the evaluation of the surface movements that took place after the completion of an earth fill dam constructed by staged construction have been evaluated by means of geodetic and geotechnical methods. Horizontal and vertical displacement measurements which were recorded between the years of 1987–1991 and 1991–1996 have been analyzed geodetically by using the Karlsruhe method. In both measurement periods, significant horizontal and vertical movements were found from adjustments and analyses of the measurements. The behavior of the dam and its foundation layers were analyzed by utilizing finite element method in two-dimensional plane-strain conditions to determine the horizontal and vertical surface movements. The results of geodetic measurements were compared with the results of the numerical analysis, and it is observed that there is a good agreement between the field measurements and computed values.

Maintaining the nation’s roads and highways is a critical national infrastructure activity. To do so requires that accurate inventories of roadway features as well as the roadway network itself be maintained. This paper addresses the accuracy of road network mileages, that is, the lengths of various road segments and routes. A study was conducted using Geographic Information Systems to determine the accuracy of using national elevation data (NED) to calculate these lengths. The advantage of doing so is that, if successful, costly and time consuming field studies could be eliminated or reduced. This savings could positively impact all State Departments of Transportation. The scope of the study includes interstate roads as well as all other road types including secondary roads. The primary contribution of the paper is its finding that using NED data provides significant advantages over field studies and provides a very acceptable accuracy level. It also identifies areas of questionable accuracy and indicates why. Additionally, the paper provides some insight into secondary road data which is an often neglected area.