I'm working with a mapir nir + red camera meaning that its blue band captures nir light and its red captures red normally.

I understand that NDVI is calculated using reflectance values. My question is how do I convert 8 bit RGB into reflectance values so that I'm able to calculate each NDVI value.
Also, does converting an image to grayscale mean its reflectance?

  • You are working with a photo camera with a normal sensor (I suppose), maybe without the ir filter. Reflectance is calculated with radiance from a spectral sensor, they are not the same – aldo_tapia Nov 14 '18 at 10:46
  • You can calculate NDVI from DN values of any bit depth., it is not necessary to convert to radiance or reflectance. This is only considered necessary when using sensor data and comparing images through time. – Jeffrey Evans Jan 12 at 1:16

Please go through this page:


This clearly tells you how to convert a DN value to reflectance. The important point to consider are multiplicative and additive re-scaling factor. As you'll clearly see, either these values are known to you (through metadata) or need to be calculated through more esoteric methods. It seems maybe the values are with OEM. If not, then there is no immediate way to convert DN values to reflectance.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.