I can't get a dialling tone https://www.friendsofbus142.com/stmap_37whvkrr.html?cialis.lidocaine.amantadine para que sirve la pastilla ibuprofeno de 800 mg The term is actually a scientific concept defined by NASA as part of the calibration process of satellite imagery. When NASA measures something with a satellite, an employee on the ground takes the same measurement. That human measurement is known as “ground truth.” If the results differ, the "ground truth" has greater credibility than the satellite does.