影像重投影是将一个影像从一个坐标系投影到另一个坐标系的过程。这通常涉及到将像素从一个平面坐标系变换到另一个平面坐标系。这可以用于许多应用中，例如建立数字高程模型（DEM）和地图制图。影像重投影通常需要进行数学计算，包括转换矩阵和插值算法，以确保像素值的准确性和精度。
这次我们将对哨兵2好数据中20m分辨率的波段，重采样到10m分辨率中，然后同一参与计算。
函数：
projection()
Returns the default projection of an Image. Throws an error if the bands of the image don't all have the same projection.
Arguments:
this:image (Image):
The image from which to get the projection.
Returns: Projection
resample(mode)
An algorithm that returns an image identical to its argument, but which uses bilinear or bicubic interpolation (rather than the default nearest-neighbor) to compute pixels in projections other than its native projection or other levels of the same image pyramid.
This relies on the input image's de