Study Of Airborne Digital Map Technique And Its Application

In the dissertation, the key realization and application techniques of airborne digital map system are studied, and in the end system simulation is also presented.The structure of airborne system is firstly discussed and then key techniques include digital map generation, storage structure, format transform, real-time terrain data update and management, airborne display etc, are studied profoundly. In this paper, full digital automatic photogrammetry method and scanning contours method to create large-scale region terrain data are presented. DMA DIED and USGS DEM format are deeply analyzed, and a new digital terrain elevation data storage format is presented. A TIN generation method is developed and can used for accelerating the 3D perspective and texture mapping display. A new effective algorithm for massive digital map data dynamic update and management, nine-grid method, is offered. Airborne digital map display, as a very important part, is studied deeply and some display schemes are offered.In order to compress digital map data as soon as possible, in this paper, a wavelet-based digital map data compression algorithm, according to the characteristic of elevation data, is presented. And some relevant key techniques include choice of wavelet, uniform quantizer with dead-zone, adaptive arithmetic coding, bit allocation and compression file structure are also emphatically studied. For this compression algorithm, how to split a quota of RMS error among all the bands so as to minimize the overall system bit rates is very important. In this paper, we propose an efficient solution to solve this optimal error allocation problem, which is based on a little-known version of Lagrange-multiplier method. Finally, compression and decompression test for different kinds of digital maps are carried out. Test results show that this technique can achieve higher compression ratio with the same given quota of RMS error compared to other compression algorithms.Threat avoidance technique is the key to integrated TF/TA2 system. For the special requirement of threat avoidance, this paper presents a fast method based on terrain visibility index to calculate danger index of each terrain grid, which solve the quantity problem of threat information on the digital map grid. Allowing for these problems that route planning in a large-scale mission area using dynamic programming usually requires excessive execution time and memory, while the gradient method usually obtains the local instead of global optimization due to the complexity of terrain surface, a genetic algorithmis adopted to do the threat route planning. Simulation results show that the optimal trajectory can avoid threat effectively and pass precisely the start and target point, can enhance effectively the aircraft's survival probability and total mission effectiveness in the flight mission.Using terrain contour matching technique, it is possible for aircraft to have a low-altitude penetration flight by no means of GPS. In this paper, terrain contour matching technique is studied, and a set of hardware and software design and realization scheme is presented. Furthermore, in order to increase the algorithm precision and real time performance, traditional terrain correlation algorithm is also unproved. And a new scheme, which terrain matching and INS error fixing are processed at some intervals according to the pre-defined matching points, is presented. In the end, a direct simulation is designed and finished. The research result will have an essential effect on the development of cruise missile in our country.