在 Google Earth Engine 中构建图像波段的数学方程式

Question

I am struggling with an equation, getting some syntax error in it, The equation is following: formula: (K2 / ln ((K1/TOA_band10)+1)) - 273.15

I am trying to do operation on image bands, but not being able to construct the right code. I have used this instead:

var BT = band_10.expression((1329.2405*1.0/((799.0284*1.0/TOA_B10)+1).log10())-273.15)

But it did not work.

A general hint about constructing an equation in earth engine - javascript.

Answer 1

You're in the right direction. You have to include the map property of expression() . It defines the variables you can use inside your expression. Then with some minor tweaks to the actual expression, it works fine:

var BT = ee.Image().expression(
  '(K2 / log((K1 / TOA_band10) + 1)) - 273.15',
  {
    K1: 799.02841,
    K2: 1329.24051,
    TOA_band10: someImage
  }
)

https://code.earthengine.google.com/e5cf09e87ddf51ec27a00b8ed4695ce4