m_map中的不同投影m_proj

常用的平面图有两种：

1.Equidistant Cylindrical

     Thisprojection is neither equal-area nor conformal. It consists ofequally spaced latitude and longitude lines, and is very often usedfor quick plotting of data. It is included here simply so that suchmaps can take advantage of the grid generation routines. Also knownas the Plate Carree. Properties are the same as for the Mercator,above.

2.

• Miller Cylindrical

• This projection is neither equal-area norconformal, but "looks nice" for world maps. Properties are the sameas for the Mercator, above.

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