An indoor transmitter is capable of programmably changing a format of a transmitter signal. A process to be performed by a position information providing apparatus comprises the step of acquiring a received positioning signal, and the step of identifying an emission source of the positioning signal, wherein, if the emission source of the positioning signal is an outdoor source, the process further comprises the step of acquiring a navigation message included in the positioning signal, and the step of performing a processing for calculating a position based on the signal, or, if the emission source of the positioning sign is an indoor source, the process further comprises the step of acquiring message data from the positioning signal, the step of acquiring coordinate values from the data, and the step of displaying position information based on the coordinate values.