A method of determining the place and location of a pelvis of a person sitting on a seat or sitting or lying on a lounger or a support, wherein the method comprises the following steps: a) detecting sitting pressures/contact pressures exerted on the seat , the lounger or the support by the ischial tuberosities and the coccyx of the person sitting essentially upright or by the iliac crests and the pubic bone of the person lying in a prone position by means of a surface sensor arranged on the seat , the lounger or the support; b) determining, by a computer unit , a first position (P 1 ) on the surface sensor at which a first peak sitting pressure/peak contact pressure exerted by a first ischial tuberosity/iliac crest of the person is reached; c) determining, by the computer unit , a second position (P 2 ) on the surface sensor at which a second peak sitting pressure/peak contact pressure exerted by a second ischial tuberosity/iliac crest of the person is reached, the second position (P 2 ) being within a predetermined distance range A from the first position (P 1 ); d) determining, by the computer unit , a distance B between the first position (P 1 ) and the second position (P 2 ); e) determining, by the computer unit , a third position (P 3 ) on the surface sensor at which a third peak sitting pressure/peak contact pressure exerted by the coccyx/pubic bone of the person is reached, the third position (P 3 ) being between the first position (P 1 ) and the second position (P 2 ), and the third position (P 3 ) being substantially on their common connecting line (C) or within a predetermined distance range on a line (D) running essentially perpendicularly to the connecting line (C); f) limiting, by the computer unit , an area (E) of the surface sensor which detects sitting and contact pressures; and g) evaluating, by the computer unit , the sitting and contact pressures of the person's pelvis in the restricted area (E) detecting sitting and contact pressures, characterized in that, for narrowing down the area (E) detecting sitting and contact pressures, the computer unit runs an iterative algorithm which depicts the Mandelbrot set . a) detecting sitting pressures/contact pressures exerted on the seat , the lounger or the support by the ischial tuberosities and the coccyx of the person sitting essentially upright or by the iliac crests and the pubic bone of the person lying in a prone position by means of a surface sensor arranged on the seat , the lounger or the support; b) determining, by a computer unit , a first position (P 1 ) on the surface sensor at which a first peak sitting pressure/peak contact pressure exerted by a first ischial tuberosity/iliac crest of the person is reached; c) determining, by the computer unit , a second position (P 2 ) on the surface sensor at which a second peak sitting pressure/peak contact pressure exerted by a second ischial tuberosity/iliac crest of the person is reached, the second position (P 2 ) being within a predetermined distance range A from the first position (P 1 ); d) determining, by the computer unit , a distance B between the first position (P 1 ) and the second position (P 2 ); e) determining, by the computer unit , a third position (P 3 ) on the surface sensor at which a third peak sitting pressure/peak contact pressure exerted by the coccyx/pubic bone of the person is reached, the third position (P 3 ) being between the first position (P 1 ) and the second position (P 2 ), and the third position (P 3 ) being substantially on their common connecting line (C) or within a predetermined distance range on a line (D) running essentially perpendicularly to the connecting line (C); f) limiting, by the computer unit , an area (E) of the surface sensor which detects sitting and contact pressures; and g) evaluating, by the computer unit , the sitting and contact pressures of the person's pelvis in the restricted area (E) detecting sitting and contact pressures, <EOS>