Applied Mechanics and Materials Vols. 353-356

Abstract: Correct resolution of ambiguities for GNSS reference network is prerequisite for generation of corrections for network RTK. Due to the presence of atmospheric delay in the double-differenced observations, the convergence time of ambiguity is about a dozen minutes and even dozens of minutes for medium and long baselines. And in the case of loss-of-lock or new rising satellites, the integer ambiguities have to be redetermined over and over again. But for the application of GNSS network RTK, the resolution of ambiguity needs to be determined real time as possible. Atmospheric delays of previous epochs are used to predict atmospheric delays of following epochs, and then wide and narrow lane combination of carrier-phase observations as well as ionosphere-free combination is used to resolve ambiguities with single epoch. Our test results show that the precision of predicted double-differenced tropospheric and ionospheric delays is about 2-3 cm using temporal-and spatial-correlation exponent model, and the success rates of L₁ ambiguities resolution with single epoch reach above 90% for medium and long distance GNSS reference station network.

Abstract: The paper introduces the Jacobi algorithm, and the Jacobi algorithm solution of linear intersection. A numerical cased is illustrated to validate the approach. The result shows the Jacobi algorithm solution is approximately equal to least squares (LS) solution, and needs no initial parameter value, and iteration. Thus, it is very important for the nonlinear adjustment, epically for the case that initial parameter value is unknown and hard to be obtained.

Abstract: DORIS is a kind of advanced space-geodetic techniques applied in satellite orbit tracking and measuring. As the first ocean dynamic environmental satellite in China, the HY-2 satellite is equipped with the Doppler orbitography and radiopositioning integrated by satellite (DORIS) tracking system for the precise orbit determination. In particular, the investigation of our work has focused on accuracy analysis of orbit determination using simulated DORIS data given different observation noises, besides the relationship is investigated between accuracy and computation time and the number of ground beacons evenly distributed around the world. Experiment results show that observation noises can affect the accuracy of orbit determination directly, and the number of DORIS ground beacons decides the accuracy and computation time of obit determination in the condition of ground beacons are evenly distributed around the world, therefore, during the process of obit determination, we should optimize the ground beacon station distribution to achieve the best accuracy of obit determination using DORIS tracking data.

Abstract: The pier construction measurement is one of the most decisive steps to ensure the quality of bridge construction, and plays an important influence in the bridge's safety and service life. This paper makes an analysis of the implementation method of pier bearing platform construction measurement of Chongqi Bridge connecting Shanghai with Suzhou, and provides a reference for similar projects.

Abstract: By using all 103 days GPS data of IGS in china, from year 2000 to 2005, the baseline is solved with GSMIT software. With One day's baseline solution as the input data, based on the mathematical floating model of station, the floating velocity of station is solved and the crustal movement is gotten; then, according to Euler theorem of plate movement, the Euler vectors of Chinese mainland is obtained; furthermore, the floating velocity of the station area in Eurasian plate is acquired. The results show that, in ITRF2000 framework, the station floating velocity is similar with what announced by IGS and so does the Euler vector, which shows that the continental shelf of China has an accelerated tendency to eastward movement.

Abstract: The traditional photogrammetric space similar transformation is used for Unmanned Aerial Vehicle (UAV) photograph digital positioning with the quite precise initial value. The new method based on the unit quaternions is presented. The rotation parameters are solved without iterative calculating and initial value. The absolute orientation is still carried out under the condition of the large angle photograph and the uneven ground control point, in which the non-linear angle parameters calculation is substituted by direct calculation. The direct calculating improves the reliability of the absolute orientation. The experiment result shows that the method is practicable and available.

Abstract: Ill-conditioned problems are widely existed in Geodesy. To resolve this problem, many experts and scholars both at home and abroad are devoted to the research of the ill-conditioned problems. And they offer the methods to dealing with the ill-conditioned problems. There are ridge estimation, generalized ridge estimation, principle components estimation, Tikhonov regularization, singular value decomposition and virtual observational approach. This text mainly generalizes the basic principle of these methods, and simply argues the development of the ill-conditioned problems.

Abstract: The study of 3D laser scanning technology in Category Conservation is one of the hot researches in recent years. Through the high-speed laser scanning, catching the 3D data of an object in large-scale with high efficiency, high accuracy and excellent resolution, is a new way in 3D reconstruction and image data acquisition. The method has achieved good results through the experiment.

Abstract: Compared with the traditional compasses, the GPS compass had many advantages, such as small volume, high precision, fast location, easy installation, low price and so on. On the paper the development status of GPS compass were introduced, then the system architecture and attitude measurement methods of the GPS compass were designed and analyzed, finally the conclusions of attitude measurements on GPS compass and its development tendency were discussed.

Abstract: In this paper landslide susceptibility mapping and model performance assessment was conducted using three models, logistic regression, GAM, and SVM, in a study area in Shenzhen, China. Ten factors, slope angle, aspect, elevation, plan and profile curvature of the slope, lithology, NDVI, building density, the distance to the river, and the distance to the fault were selected as influencing factors for the landslide occurrences. All three models were trained and the resulting susceptibility maps were created. The performances of the three models were then assessed by AUC values through a 10-fold cross-validation. It could be concluded that in the study area GAM had the best overall performance among the three models, while SVM was better than logistic regression. Based on the derived DPR values, the optimum thresholds between stable areas and risky areas for all three models were also determined.