Measurement of the length of pedestrian crossings - a navigational aid for blind people

This paper describes a fast as well as simple method for measurement of the length of pedestrian crossings using a single camera for the purpose of a travel aid for blind people. In a crossing, the usual black road surface is painted with constant width periodic white lines. In Japan, this width is 45 cm. The crossing region as well as its length is detected using this concept. At first, the crossing direction is determined from the power spectrum using fast Fourier transform. The periodic white and black bands are detected using integration along the crossing direction and differentiation of the integral data perpendicular to the crossing direction. Then the crossing length is calculated using the number of white and black bands in the crossing region. Experiment is performed using real road scenes with pedestrian crossing. The technique is successful in measuring the length of the crossing with high accuracy if the image resolution is good and the white paintings on the crossing are fine.