Geospatial best fit - Histogram against continous measured data?

#1
Hi,

I have some remote sensing images from which I extracted the pixel values as histogramms:

Pixel value respectively classes 1 - 255

example:

Picture 1: NDVI
Value-Count
1-3565
2-0
3-0
4-564
5-665
6-0
7-0
8-3
.
.
.
255-123

Picture 2: Near Infrared
Value-Count
1-0
2-2236
3-12
4-123
5-26
6-2220
7-30
8-0
.
.
.
255-156

and I have some ground measured, continous data:

Plant height in cm
254
211.5
243.5
250.5
220.6
231.8
268.8
256.5
232.6
258.4
221.8
245.4
250.3
248.9
237.6
237.7
200.8
240.7


Which statistical test do I need in order to explain, which Index (=Histogramm of pixelvalues) best explains (or fits) the measured data (plant height in cm)?

I am working with R.

I would be really thankful and can offer you a coffe in the cryptocurrency of your choice for helpful suggestions.

Cheers
Tommy