Journal of Surveying Engineering

A linear transformation, including a similarity model and an affine model, plays an important role in reference frame transformation problems. It establishes geometric relations between different reference frames by adopting physically interpretable parameters, and allows one to integrate positional coordinates across various systems. In this study, an analytical noniterative approach for solving the indirect problem (i.e., parameter estimation) of a linear transformation model is proposed. It gives a closed-form solution for the transformation without any prerequisite on the magnitude of parameters. Consequently, neither good initial values nor iterations are required during the parameter estimation process. Through numerical examples, it is illustrated that the proposed approach is capable of giving accurate parameter estimates as a classic least-squares technique does, but with much higher computational efficiency. In a reference frame transformation problem of 1,000 control points, the proposed approach takes less than 0.1 s to produce an accurate solution, while an ordinary least-squares approach takes 10–17 s to finish the same analysis. With the above advantages, this approach would especially benefit the cases in which a real-time application or large network is involved in an analysis.

Global Positioning System (GPS) is widely used for monitoring some natural phenomena and man-made structures. The detection of the deformation epoch in real time is of great importance in these applications. This study is concerned with designing algorithms to detect the deformation epoch in order to improve the quality of GPS measurements for the real-time deformation applications. In this regard, the multiple Kalman filters model based on the idea of model selection is proposed to improve the reliability of the detection of the deformation epoch. For the model selection, the proposed model makes use of the statistical criterion comparison in each case instead of the hypothesis test. The model with the lower value of the statistical criterion is to be preferred. According to the statistical criterion, the optimal Kalman filter model can be selected to describe the time series and to identify the deformation epoch at each epoch. The simulated data and the GPS kinematic time series are used to verify the effectiveness of the multiple Kalman filters model.

Reflectorless distance measurement provides the ability to easily make quick measurements saving time and labor for surveyors. The precision and accuracy of these types of measurements are under discussion because of the variety of parameters that can affect these measurements that are not well-understood. This paper attempts to answer some of the questions that have arisen about the credibility of reflectorless distance measurements ranging up to 50 m. An experiment was carried out using 26 different materials as the reflecting surface (these materials were also of differing colors). Additionally, the experiment used three different angles of incidence of the incoming electromagnetic energy with three different types of reflectorless total stations over a variety of ranges. A further experiment was conducted with an additional total station using 11 different materials at different ranges. To properly evaluate the results, a special supporting base was manufactured for holding the reflecting surface to ensure accuracy in the evaluation. The results are presented in tables and the conclusions that are derived indicate that further investigation is needed, especially at longer distances, as the parameters that influence reflectorless distance measurement in those situations are many more, and more important than at short ranges.

A new geodetic method for accurate determination of nearshore wave characteristics is proposed. This method is based on a robotic total station set on stable position on the coast and aiming at a passive reflector mounted on a buoy, usually at a distance of a few hundred meters. This method permits the identification of the changing three-dimensional coordinates of the reflector/buoy in a selected, fixed coordinate system independent of the buoy with centimeter accuracy, and a rate of up to 6 Hz, and it can even determine very precisely waveforms, including those with steep sides. The effectiveness of the method is demonstrated on the basis of results of two cases studies. While this method provides exceptional quality results for small waves, it can also be used for large waves as well, and especially to calibrate other wave measurement techniques. Techniques to avoid clipping effects usually affecting the wave measurements and the possibility to measure the wave and current direction are also discussed.