This chapter first reviews recent pilot studies covering limited areas often with exposed bare soils. Then we focus on the challenges for large-scale application of spectral mapping when the soil and parent material are heterogeneous and surface conditions are unknown. In order to deal with these constraints we discuss i) calibration of spectral models based on large spectral libraries, ii) surface conditions that disturb the soil signal, and iii) time series of images in order to delimit cropland fields and increase the extent of bare soil that can be mapped. Finally, a case study deals with a SOC prediction map derived from the spectra of a Sentinel-2 image and calibrated using the LUCAS spectral library.