There is provided a method of detecting erroneous measurements of the position of a device, the device comprising position measurement means, the method comprising determining the state of motion of a user of the device from a plurality of possible states predicting the position of the device using a plurality of models and the determined state of motion of the user, each model corresponding to a respective one of the plurality of possible states measuring the position of the device using the position measurement means comparing the predicted position of the device to the measured position of the device and determining whether the measured position of the device is erroneous based on the result of the step of comparing.
