Verification of remote sensing data is essential to calibrate methods and ensure acceptable levels of accuracy. For this research project the Terra-I remote sensing data was validated using government statistics on cocoa production and knowledge of CIAT colleagues. However field verification is normally the preferred and most accurate (though generally most expensive) validation technique.
The below link is to an informative blog post about a field verification exercise carried out for Terra-I data in the Peruvian Amazon. The data to be validated included over 25,000 ha of land cover loss from between 2004 and April 2015. The verification exercise used Terra-I data for 2013, 2014 and 2015 to define 65 sampling points and then using three buffer zones, randomly selected pixels for field validation.
http://www.terra-i.org/news/news/Validating-Terra-i-in-the-Peruvian-Amazon.html