Geo-spatial Information Science

To overcome the shortcomings of the traditional multibeam survey and data processing, a new method is presented for the precise determination of the instantaneous height at the multibeam transducer by the blend of GPS height and heave signals. Before signal blend, GPS height and heave signals need to be corrected first to the transducer center by attitude correction. Second, the GPS height needs to be checked and modified by heave check and modification itself. Butterworth and FFT (fast Fourier transformation) were used in the signal blend. Finally, FFT is thought to be appropriate in signal processing. The new method efficiently overcomes the shortcomings of the traditional method, and this is proven well by the MBS (multibeam bathymetric system) experiment.

In the field of converting simulation surveying and traditional close range photogrammetry, it has been developed so far to survey objects by commercial digital camera and this technique is applied widely in every part of production. In order to get three-dimensional information of objects, commercial digital camera must be examined. For a long time, digital camera has been examined by DLT. Then there must be a high-precision control field. For realizing surveying without control points, a method for self-calibration is proposed.

The coastal lowlands in northern Jiangsu Province, China, is characterized by low relief and low water surface gradient in streams. The flooding stages are commonly lower than the high-tide level and the tidal range is relatively small. All these factors prohibit rapid discharge of floodwater and make the flood regimes here extremely sensitive to the sea level rise. The 1991 Plum Rain was examined, when precipitation was significantly higher than normal. The one-dimensional open-channel non-conservative flow model was used to simulate the stream flow in the channel network of studied area. GIS technology was used to delineate the maximum in undated area by analyzing the DEMs.

Data obtained via airborne position and orientation system (POS) is in WGS 84 global geocentric reference frame, while the national coordinate reference system for topographic mapping in China is generally Gauss-Kruger projection coordinate system. Therefore, data obtained via a POS must be transformed to national coordinate system. Owing to the effects of earth curvature and meridian deviation, there are some errors in the process of angle transformation from roll, pitch, and heading (Φ,Θ,Ψ) obtained directly via a POS to the attitude angles of images (φ,ω,κ) needed in photogrammetry. On the basis of effect theories of earth curvature and meridian deviation on exterior orientation angular elements of images, a method using a compensation matrix to correct the transformation errors from attitude angles obtained via the POS to exterior orientation angular elements of images is proposed in this paper. Moreover, the rigorous formula of the compensation matrix is deduced. Two sets of actual data obtained via a POS AV 510, which are different in scale and terrain, are selected and used to perform experiments. The empirical results not only indicate that the compensation matrix proposed in this paper is correct and practical but also show that transformation accuracy of exterior orientation angular elements obtained via the POS based on compensation matrix is relevant to the selection of vertical axis (a projection of central meridian) of Gauss-Kruger projection coordinate system; the proper vertical axis should be the Gauss-Kruger projection of the central meridian of projection zone in which the survey area locates. However, the transformation accuracy of exterior orientation angular elements is irrelevant to the choice of origin of coordinate system; it is appropriate that the origin of coordinate system locates at the center point of the survey area. Moreover, transformation accuracy of exterior orientation angular elements achieved based on the compensation matrix deduced in this paper is higher than that obtained via the existing POS processing software.

Acquisition and registration of terrestrial 3D laser scans is a fundamental task in mapping and modeling of cities in three dimensions. To automate this task marker-free registration methods are required. Based on the existence of skyline features, this paper proposes a novel method. The skyline features are extracted from panoramic 3D scans and encoded as strings enabling the use of string matching for merging the scans. Initial results of the proposed method in the old city center of Bremen are presented.

Close-range photogrammetry is to determine the shape and size of the object, instead of it's absolute position. Therefore, at first, any translation and rotation of the photogrammetric model of the object caused by whole geodesic, photographic and photogrammetric procedures in close-range photogrammetry could not be considered. However, it is necessary to analyze all the reasons which cause the deformations of the shape and size and to present their corresponding theories and equations. This situation, of course, is very different from the conventional topophotogrammetry. In this paper some specific characters of limit errors in close-range photogrammetry are presented in detail, including limit errors for calibration of interior elements for close-range cameras, the limit errors of relative and absolute orientations in close-range cameras, the limit errors of relative and absolute orientations in close-range photogrammetric procedures, and the limit errors of control works in close-range photogrammetry. A theoretical equation of calibration accuracy for close-range camerais given. Relating to the three examples in this paper, their theoretical accuracy requirement of interior elements of camera change in the scope of ±(0.005–0.350) mm. This discussion permits us to reduce accuracy requirement in calibration for an object with small relief, but the camera platform is located in violent vibration environment. Another theoretical equation of relative RMS of base lines (m S/S) and the equation RMS of start direction are also presented. It is proved that them S/S could be equal to the relative RMS ofm ΔX/ΔX. It is also proved that the permitting RMS of start direction is much bigger than the traditionally used one. Some useful equations of limit errors in close-range photogrammetry are presented as well. Suggestions mentioned above are perhaps beneficial for increasing efficiency, for reducing production cost.

Mineral resource potential mapping is a complex analytical process, which requires the consideration and the integration of a number of spatial evidences like geological, geomorphological, and wall rock alteration. The aim of this paper is to establish mineral exploration model for copper, lead, and zinc in Lanping basin area using the capability of analytical tools of Geographic Information System (GIS) and remote sensing data to generate maps showing favorable mineralized area. The geo-exploration dataset used for the research includes copper, lead, and zinc deposits, geological maps, topographic maps, structural maps, and ETM+ imagery. Geological features indicative of potential copper, lead, and zinc were extracted from the datasets input in the predictive model. The method of weights of evidence modeling is a probability-based technique for generating mineral potential maps using the spatial distribution of indicative features with respect to the known mineral occurrences. The method of weights of evidence probabilistic modeling provides a quantitative method for delineating areas with potential of copper, lead, and zinc mineral deposits in the Lanping Basin area. weights (W+, W−) and contrast (C=(W+)-(W−)) calculations guide the data-driven modeling. The four most important spatial features for exploration guide for copper, lead, and zinc mineralization hosted in the Lanping Basin area are alteration zones, faults, host rocks, and lineaments. The host rocks and deep faults have the strongest spatial association with the known copper, lead, and zinc deposits. The hydrothermal alteration zones have the moderate spatial association with the copper, lead, and zinc deposits. The predicted high-favorability zones do not show the strong affinity with lineaments. The distribution of 22 (copper, lead, and zinc) occurrences in the Lanping Basin was examined in terms of spatial association with various geological phenomena. The analysis of these relationships using GIS and weights of evidence modeling has predicted areas of high and moderate mineral potential, where a little or no mining activities exist.

Because of quick development of cities, the update of urban GIS data is very important. Change detection is the base of automatic or semi-automatic data update. One way of change detections in urban area is based on old and new aerial images acquired in different durations. The corresponding theory and experiments are introduced and analyzed in this paper. The main procedure includes four stages. The new and old images have to be registered firstly. Then image matching, based on the maximum correlation coefficient, is performed between registered images after the low contrast areas have been removed. The regions with low matching quality are extracted as candidate changed areas. Thirdly, the Gaussian-Laplacian operator is used to detect edges in candidate changed areas on both the registered images, and the straight lines are detected by Hough transformation. Finally, the changed houses and roads can be detected on the basis of straight line matching in candidate changed areas between registered images. Some experimental results show that the method introduced in this paper is effective.

On the basis of a sinusoidal model of the disturbed horizontal acceleration, the spectrum characteristics of misaligned angle and horizontal acceleration correction are analyzed. In an airborne gravimetry test, the misaligned angle of platform and horizontal acceleration correction are calculated. They are 5′ and 3 mGal, respectively, when the flight is stable.