A method comprising: determining, by a mobile computing device and based on first motion data generated by a motion sensor of a mobile computing device, that a user associated with the mobile computing device is riding in a vehicle; after determining that the user associated with the mobile computing device is riding in the vehicle; determining, by the mobile computing device and based on second motion data generated by the motion sensor of the mobile computing device, that a change in an angle of the mobile computing device relative to gravity satisfies a threshold amount of change; responsive to determining that the change in the angle satisfies the threshold amount of change, initiating, at a first position of the mobile computing device, storage of third motion data generated by the motion sensor, wherein the first position is a reference position; responsive to determining that the change in the angle of the mobile computing device relative to gravity satisfies the threshold amount of change, determining, by the mobile computing device and based on the third motion data, that the user of the mobile computing device is traveling on foot, wherein the reference position corresponds to a location at which the user exited the vehicle; determining, by the mobile computing device and based on an external signal, a second position of the mobile computing device, wherein the second position is a current position of the mobile computing device that is different from the reference position; responsive to determining the second position of the mobile computing device, determining, by the mobile computing device, based on the third motion data and the current position, the reference position of the mobile computing device; storing, by the mobile computing device, an indication of the determined reference position as the location at which the user exited the vehicle; retrieving, by the mobile computing device, a position history of the mobile computing device, the position history including a plurality of previously determined reference positions of the mobile computing device, wherein the reference position of the mobile computing device is included in the plurality of previously determined reference positions; determining, by the mobile computing device, a subset of the plurality of previously determined reference positions located within a threshold distance from the current position of the mobile computing device; and outputting, by the mobile computing device and for display, a graphical indication of one or more of the subset of the plurality of previously determined reference positions. determining, by a mobile computing device and based on first motion data generated by a motion sensor of a mobile computing device, that a user associated with the mobile computing device is riding in a vehicle; after determining that the user associated with the mobile computing device is riding in the vehicle; determining, by the mobile computing device and based on second motion data generated by the motion sensor of the mobile computing device, that a change in an angle of the mobile computing device relative to gravity satisfies a threshold amount of change; responsive to determining that the change in the angle satisfies the threshold amount of change, initiating, at a first position of the mobile computing device, storage of third motion data generated by the motion sensor, wherein the first position is a reference position; responsive to determining that the change in the angle of the mobile computing device relative to gravity satisfies the threshold amount of change, determining, by the mobile computing device and based on the third motion data, that the user of the mobile computing device is traveling on foot, wherein the reference position corresponds to a location at which the user exited the vehicle; determining, by the mobile computing device and based on an external signal, a second position of the mobile computing device, wherein the second position is a current position of the mobile computing device that is different from the reference position; responsive to determining the second position of the mobile computing device, determining, by the mobile computing device, based on the third motion data and the current position, the reference position of the mobile computing device; storing, by the mobile computing device, an indication of the determined reference position as the location at which the user exited the vehicle; retrieving, by the mobile computing device, a position history of the mobile computing device, the position history including a plurality of previously determined reference positions of the mobile computing device, wherein the reference position of the mobile computing device is included in the plurality of previously determined reference positions; determining, by the mobile computing device, a subset of the plurality of previously determined reference positions located within a threshold distance from the current position of the mobile computing device; and outputting, by the mobile computing device and for display, a graphical indication of one or more of the subset of the plurality of previously determined reference positions.