NDVI was a concept that took me a while to get to grips with; this formed part of one of the practical’s I had to do. I found this a very difficult area to understand however, after doing some research it became a lot clearer. I learnt that as vegetation reflects most in the NIR band due to the air gaps in the structure of the leaf, it allows NIR radiation to freely pass through and return to the sensor. So, by looking at the amount of energy being reflected it is possible to see different characteristics. So, -1 on the scale would show a soiled surface as there is little NDVI reflection where as an NDVI value closer to +1 would indicate healthy dense vegetation (Cihlar, 2000). From learning this simple principle, its helped greatly to answer the practical questions.
Cihlar, J. (2000). Land cover mapping of large areas from satellites: Status and research priorities. International Journal of Remote Sensing, 21(6-7), pp.1093-1114.
Feature image Reference-
Agribotix (2017). NDVI principles. [image] Available at: http://agribotix.com/blog/2014/06/10/misconceptions-about-uav-collected-ndvi-imagery-and-the-agribotix-experience-in-ground-truthing-these-images-for-agriculture/ [Accessed 20 Apr. 2017].