Google Earth Engine（GEE）——GEE自带的归一化指数计算工具介绍
作者：互联网
上一篇当中有介绍直接通过波段运算，但是更好的方式是通过内置的算法来实现，这样适配性问题会更好一些
normalizedDifference(bandNames)
Computes the normalized difference between two bands. If the bands to use are not specified, uses the first two bands. The normalized difference is computed as (first − second) / (first + second). Note that negative input values are forced to 0 so that the result is confined to the range (-1, 1).计算两个波段之间的归一化差异。如果没有指定要使用的频段，则使用前两个频段。归一化差值的计算方法是（第一-第二）/（第一+第二）。注意，负的输入值被强制为0，这样结果就被限制在（-1，1）的范围内。
Arguments:
this:input (Image):
The input image.
bandNames (List, default: null):
A list of names specifying the bands to use. If not specified, the first and second bands are used.
Returns: Image
Map.setOptions("SATELLITE");
var image 标签：Engine,bands,specified,second,GEE,归一化,input,first 来源： https://blog.csdn.net/qq_31988139/article/details/121125631