Journal of Surveying Engineering

In order to combat the influences of both outlier and multicollinearity on geodetic adjustments, a new robust-biased estimation method is proposed by combining outlier identification with biased estimation. The estimation scheme is roughly divided into two steps. First, quasi-accurate detection of gross error (QUAD) is used to detect outliers and correct observations. Then the “clean” observations and biased estimations are used to obtain more accurate estimates of unknown parameters. Several selection schemes of the biased parameters included in the biased estimators based on QUAD are given in detail. A numerical example illustrates that the new robust-biased estimation method not only can resist the bad influence of outlier and effectively overcome the difficulty caused by multicollinearity simultaneously, but also is far more accurate than least-squares estimation, biased estimation, robust estimation, and generalized shrunken type-robust estimation.

This paper describes an automatic approach in architectural photogrammetry for the documentation and analysis of historic facades. Multispectral close-range images were taken and evaluated for identification of masonry wall materials. Digital image processing and close-range photogrammetric techniques were used to identify, nondestructively recognize, and map the materials and damages of a historic facade. Two supervised classification algorithms were analyzed: Maximum likelihood and minimum distance. Although the maximum likelihood was somewhat slower, it provides much higher classification accuracy than the minimum distance classifier. Additional to the statistical data, thematic images were obtained semiautomatically for visualization, management, and decision-making purposes.

In this paper, global positioning system (GPS) data collected by seven permanent GPS stations of Southern California Integrated GPS Network during the launch of the long-range Minuteman II missile from Vandenberg Air Force Base on July 8, 2000 is processed. By manipulating and passing the total electron content through a high-pass filter, the energy released by the missile launch was detected. After that, the basic concept of positioning used in GPS is applied to the problem to pinpoint the position of the missile launch pad. This is done by the implementation of the concept of subionospheric points that serve analogously to GPS satellites. The simulation of the analysis with prior data proves that the launch pad can indeed be positioned with this algorithm. However, real-life analysis without prior data highlights the existence of three problems that need to be overcome to pinpoint that pad.

Layout is one of the most important missions of the surveying engineer, which aims to carry out the designed horizontal and vertical geometries of an engineering structure by satisfying the required accuracies. It is necessary to satisfy the required accuracies through the “achieved point standard deviation” which is defined by the product of the errors derived from known point coordinates and the layout measurements. In order to satisfy the required accuracy, the achieved accuracy should be smaller than the required one. The mission of the surveying engineer is planning the layout process by taking into consideration the required and the achieved standard deviations. In this paper, the planning process concerning the measurement error components is explained. The issues regarding the network design, the measurements, and the selection of the proper instruments for the layout are explained to make optimal decisions. The given decision making methods in this study are rather valuable in the special applications which require high accuracy.

A computer program has been developed for the reduction of trilateration data. The program is general in that it will handle any control figure that a user might specify. Data validation is a key feature of the program. Input data from surveys are extensively checked for errors, and warning messages are displayed on the screen when an error is encountered. As a further aid in diagnosing errors, the program allows the user to print out intermediate results so that they may be examined for discrepancies. Least-squares adjustment of coordinates is provided.

This work presents a tool for supporting the management and monitoring of water resources. This tool is a geographical information system, modeled and structured to be applied in watersheds, facilitating diagnosis and helping decision making through the correlation of environmental and social economic variables