Tomography using drone-borne synthetic aperture radar (SAR) has proven to be very useful and efficient in surveying the subsurface of areas with gravimetric soil moisture ranging from 0 to 50%. The drone-borne SAR, along with the back-projection processing algorithms, and the proof of concept through the detection of a corner reflector buried 1.7 meters deep in clayey soil, are presented. Anthills with areas ranging from 0.05 m2 to 120 m2 were detected under an industrial eucalyptus forest, with a detection probability of more than 80% in two different regions.