A device for estimating a current orientation of a mobile terminal device at a current geographical position, wherein, at the current geographical position, a current measurement package may be determined which has a transmitter identification and an electromagnetic signal characteristic of a radio transmitter which may be received at the current geographical position with the current orientation of the mobile terminal device at a current measurement time, with a determiner for determining an accordance measure between the current measurement package and a reference measurement package, which has a transmitter identification, a reference orientation and an electromagnetic signal characteristic of a reference radio transmitter which was receivable at a geographical reference position allocated to the reference measurement package with the reference orientation at a reference time lying before the current measurement time, a selector for selecting at least one reference measurement package which has an accordance measure, and a determiner for determining an estimate for the current orientation of the mobile terminal device based on the reference orientation of the at least one selected reference measurement package.