A portable unit for detecting a position with respect to a reference, particularly for substantially shielded environments, comprising a power supply element, further comprising a control and processing processor, a device for three-dimensional orientation with respect to geographical references, at least one accelerometer, a screen, a memory component and respective data input and output interfaces, said processor being adapted to be preset by the user by means of said input interface and being adapted to process instantaneously data supplied during use by said orientation device and by said at least one accelerometer, displaying said processing on the screen and storing said processing in the memory component.