Method, hardware, device, computer program, and apparatus for positioning mobile devices in unmapped locations based on motion sensor and radio frequency measurements are described. A reference radio signal is received from a transmitter with an unknown absolute position and a reference range measurement is calculated. Mobile device motion sensor data is used to estimate a relative position of the mobile device. A sample radio signal is received from a transmitter with an unknown absolute position and a sample range measurement is calculated. The reference range measurement and the sample range measurement are compared. The estimated motion sensor based position is adjusted according to the result of the comparison.