Estimate soil sealing with NDVI


i try to estimate the soil sealing percentage of Frankfurt am Main. A Region with Rivers, Urban Areas, Crops, Forest and Soil. I create the NDVI of a Sentinal 2 Image in the Vegetation Period to get strong reflectance on Green Vegetation. It worked verry well except the fields where no crop is growing. The soil there have nearly the same values like the streets and houses.

Maybe you have an idea to solve this Problem? Another Index i can use? Or should i use a supervised classification instead? Any Experience with this sealing topic ;)? Thank you for you help!

Best regards

This should be a suitable application for the spectral unmixing module. You collect reference spectra (3-4 classes at best, including sealed soil), format them as a table and give them to the operator. Output is a band containing the fraction of each pixel containing each class.
Have a look at the help menu, it is well documented. Additionally, you will find some examples in this forum using the search function.