Due to the limit of traditional UAV navigation control, this paper puts forward a kind of navigation control system that is based on the strategy of multi-model variable structure intelligent control.

针对传统无人机导航控制的局限性，提出基于多模变结构智能控制策略的导航控制系统。

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The upper-limit of the positioning dilution of precision(PDOP) is an important index to design of a navigation constellation and evaluation of its performance.

定位精度因子（PDOP）上限取值是导航星座设计及其性能评价的基本依据。

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This problem is augmented by the fact that there is no limit to the number of entries that can be stored in the back and forward stacks of navigation history.

这个问题会不断扩大，因为并没有限制在巡览记录的向后及向前堆叠中，能够储存多少项目。

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Ovi Maps beta adds visibility to subways, trams and trains in 85 cities around the world, real-time traffic, safety alerts in or out of navigation mode, visibility to parking and petrol stations, and speed limit warnings.

ENGADGET: Nokia announces new C6 and C7 Symbian^3 handsets with 8 megapixel cameras, 720p video