The purpose of navigation is to ascertain the present position and to determine the speed, direction, etc.
After World War II electronic aids to navigation developed very rapidly and, to a great extent, replaced more traditional tools.
Electronic speed and depth finders have totally replaced their older counterparts.
As technologies are developed, designers and engineers have also turned their attention to minority groups like people that are visually impaired.
In this case, Electronic Travel Aid are developed to target the needs of visual impaired individuals for obstacle identification as well as navigation of the surrounding to enhance mobility.