A mobile plant for orienting a tool with respect to a hole is provided. The plant includes an arm assembly for supporting a tool wherein the tool is adapted to be lowered into the hole. The plant also includes a primary sensor for sensing the geographical location of the tool, and a secondary sensor for sensing the location and/or orientation of the hole. In use, the plant adjusts the position of the tool supported by the arm assembly based on the geographical location sensed by the primary sensor and the location and/or orientation sensed by the secondary sensor, in order to align the tool supported by the arm assembly with the hole.