Any iPhone apps for fine-resolution mapping?
Clearly, there aren't any popular apps that replicate an Inertial Navigation System which is what you describe.

The wikipedia article I link above illustrates that the integration errors that crop up from this sort of apparatus build up over time and errors of hundreds of meters are possible after only an hour of operation.



GPS would be far more accurate than inertial calculations given the limitations and lack of precise calibration of the gyroscope sensors within an iOS device. They are designed to detect gross movements (10-25 degrees) and other tools like laser or echo location would be needed to measure a path over a 50 meter span more accurately than GPS will allow.