In many practical applications, the position of a target is usually found in polar coordinates or sphere coordinates, not in Cartesian coordinates.
在许多实际情况中，目标测量值通常在极坐标或球坐标中得到，而不是在笛卡尔坐标中得到。
2
The development of spectral method on elliptical and hyperbolic problems is summarized, and spectral method under sphere coordinates and polar coordinates is touched too.