The Tilli Portable Tiltmeter consists of a rugged stainless steel frame with aluminium sensor housing containing the MEMS technology inclinometer. The surfaces of the frame are machined to allow an accurate positioning of the tiltmeter during measurements. Measurements can be done on horizontal or vertical surfaces. Readings in two orthogonal directions can be obtained rotating the instrument of 90° only on the horizontal surface. Coniugated measurements (180 degree rotation) eliminate instrumental and mounting offset.