在地图等积投影中，椭球面梯形面积的正、反算方法和精度是关键。

In order to satisfy the requirement of high precision in map equiareal projection, the precise forward and inversion formulas of ellipsoid trapezoid area are studied out according to the basic theory.

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投影网格的目的是用存在于投影空间的网格代替传统的存在于世界空间的规则矩形网格或梯形网格，使网格采样过程符合人眼视线规律的自然属性。

The projective grid, whose sampler takes the view rule of human eyes into account, is designed to use the grid in projective-space to take the place of the traditional grid in world-space.

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投影网格的目的是用存在于投影空间的网格代替传统的存在于世界空间的规则矩形网格或梯形网格，使网格采样过程符合人眼视线规律的自然属性。

The projective grid, whose sampler takes the view rule of human eyes into account, is designed to use the grid in projective-space to take the place of the traditional grid in world-space.

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