Indoor rotation sensor and directional sensor for determining the heading angle of portable device

A method for determining a heading angle of a portable electronic device in an indoor environment comprising:

• providing an orientation model describing how rotational movement is integrated to orientation;
• receiving rotational movement information from a rotational sensor of the portable electronic device, the rotational movement information being indicative of rotational movement of the portable electronic device;
• determining a first heading angle of the portable electronic device at the processor based on the received rotational movement information and the orientation model and then computing the orientation around the downward direction of the portable electronic device to form the first heading angle;
• receiving first direction information from a first direction sensor of the portable electronic device;
• receiving second direction information from a second direction sensor, wherein the second direction information is indicative of a direction of movement of the portable electronic device;
• using the processor of the portable electronic device, identifying an outlier that is one of said first and second direction information, the outlier comprising information that is inaccurate due to an occurrence of a disturbance;
• and
• computing a correction to the heading angle at the processor of the portable electronic device by comparing the heading angle to the first and second direction information and considering the outlier.