Table 4.

Comparison with navigation systems developed in the last decade for visually impaired people.

References	Year	System	Cost	Accuracy	Testing				Limitations
					Indoor/outdoor	Tested by	Test	Feedback
[23]	2003	NavBelt and the GuideCane	High	Good	Both	Blindfolded	Obstacle avoidance and natural walking	Binaural feedback system and haptic feedback	Ultrasonic sensor cannot detect all objects under all conditions, NavBelt is slow but GuideCane is fast; however, a number of sensors need more power.
[24]	2007	Ultrasonic sensor	Medium	Low	Indoor	Blindfolded	Task completion	Vibrotactile	Needs some surface for producing distance output; sound waves get absorbed in some surfaces like sponge, cloth, skin, and so forth.
[25]	2011	Hybrid ultrasonic, camera, and eBox	Medium	Indoor		Blindfolded	Obstacle avoidance and recognition	Voice	Not tested in outdoors, difficult to manage multiple sensors. Ultrasonic sensor has limitations of giving false data for some surfaces discussed before.
[27]	2012	Wearable Navigation System using SLAM	Medium	Medium	Both	Blindfolded	Path following	Verbal feedback	Complex computation for SLAM using landmarks.
[28]	2012	Electronic cane	High	Good	Indoor	Blindfolded	Obstacle avoidance	Verbal feedback	Five sensors are integrated to gather obstacles' data; therefore, malfunctioning of any one of them can cause system failure.
[29]	2013	Smartphone based navigation assistance	Low	Medium	Outdoors	Blindfolded	Obstacle avoidance	Verbal feedback	Training data is required and robust obstacle detection is required.
[26]	2013	Hybrid, Infrared, and ultrasonic	Low	Both		Blindfolded	Obstacle avoidance	Vibrations	Infrared sensor is unable to work under strong sunlight; similarly, ultrasonic sensors get effected by loud environmental noises such as hissing sound produced by air houses.
[30]	2015	Robot Guide	High	Medium	Indoor	Blind	Natural walking	Verbal feedback	A big robot that needs space for its own movement can only walk on smooth surfaces.
[8]	2015	Infrared sensor	Low	Low	Indoor	Blindfolded	Travel time	Melodies	Infrared sensor alone is not reliable because of its blindness under strong light and rough surfaces.
Our system	2015	Combined vision techniques and depth map from Kinect	Low	Good	Both	Blind and blindfolded	Obstacle avoidance and walking in natural environment	Verbal feedback	Infrared sensor is unable to work under strong sunlight.