According to several project evaluations, you should normally obtain a deviation of less than 2%, sometimes even less than 1%. This is, of course, depending on local formation, equipment set-up and driller’s skills. Top hammer drilling normally starts deviating after 15 meters. Drilling with air-powered equipment often gives a major deviation after some dozens of meters. Compared to diamond core drilling, the Wassara technology gives same accuracy. Although, the diamond core drilling is much slower.