Simulating real virtual ocean environment is necessary for the research of interaction simulation of underwater gravity aided inertial navigation system. One of the key techniques of realizing virtual ocean environment is modeling and simulating three-dimensional ocean waves. Numerical simulation of three-dimensional ocean waves in the case of different wind speeds is realized using MATLAB based on directional spectrum composed of Pierson-Moscowitz frequency spectrum and directional spreading function. Experiments show that the simulation speed is fast and the simulation results are vivid if suitable simulation frequency band, interval of wave frequency and interval of direction angle are selected. The simulation can provide some technological supports for interaction simulation of gravity aided navigation system for underwater vehicles.
In this paper, the implementing method of updating the coal mining area’s DEM by mining subsidence forecast data is introduced. The data file of mining area’s elevation points can be generated by extracting from the digital topographic map of coal mining area, and after the interpolation and encryption of extracting mining area’s elevation points, the data file of the mining area’s collapse can be obtained by subtracting the values of the subsidence forecast from the elevation values of the mining area’s elevation pionts. According to the data file of the mining area’s collapse, DEM of the mining area’s collapse can be generated, and the corresponding contour map can be also generated. This has important significance for the environmental management and disaster prevention engineering design of coal mining area.
Using the ordinary digital camera to obtain the single image of the ancient building there are three sets of parallel lines perpendicular to each other, the model has been established to solver 3D relative coordinates of the ancient building according to the pixel coordinates of the ancient building. As long as a basic length of ancient building is measured, using the calculated 3D relative coordinates, the real structure size of the ancient building will be fully restored, and so the elevation drawing of the ancient building will be also drawn. The method has an important practical significance for the protection of ancient building.
Integer ambiguity resolution is a prerequisite for GPS reference station network. Due to the presence of distance errors in the double-differenced data (principally atmospheric delays), the convergence time of ambiguity in medium and long distance GPS reference station network is about a dozen minutes and even dozens of minutes. And in the case of loss-of-lock, cycle-slips or new rising satellites, the integer ambiguity value have to be redetermined over and over again. But for the application of GPS network RTK, the resolution of ambiguity needs to be determined real time as possible. This paper described techniques to predict atmospheric biases using exponent model and AR model from derived the atmospheric delays by previous epochs, which is helpful for rapid solution of ambiguity and generation of error correction in the GPS reference station network. Experiment shows that the precision of predicted atmospheric delays is about 2-3 cm using temporal- and spatial-correlation exponent model and AR model in medium and long distance GPS reference station network.
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