面向瓦片金字塔的层深确定与投影变换方法

为了提高瓦片金字塔变换效率，结合数字地球的视域模型，建立一个15参数的四次多项式投影变换方法，从理论上探讨瓦片大小选择的影响因素，给出瓦片大小和瓦片金字塔层深的优化方法，并且采用JOGL构建一个基础数字地球环境BDE2对算法进行测试。分析与实验结果显示：该算法构建的像素精度为10m的瓦片金字塔层深仅为10，投影变换误差未超过5×10-5，且算法复杂度低、拼接紧密、清晰度高、失真小，能够有效地避免变换后影像的拼接裂缝和特征失真。

Layer depth determination and projection transformation method oriented to tile-pyramid

In order to improve the transformation efficiency of tile-pyramid image, a 15-parameter projection transformation method was established by quartic polynomial based on the view model of digital earth. The influencing factors for selecting the size of tile image were discussed theoretically, and an optimization method to determine the size and depth of tile-pyramid was given. To test this algorithm, a basic digital earth environment BDE2 was constructed by adopting JOGL. The analysis and experimental results show that tile-pyramid in 10m pixel accuracy constructed by this algorithm only has 10 layers and less than 5×10-5 average error; meanwhile, the proposed algrithm has low complexity, close stitching, high definition and low distortion, and can effectively avoid stitch cracks and characteristics distortion after the image is transformed.