1. Dep-t of Defence, Global positioning system standard positioning service performance standard, 4-th edition (2008). http://www.gps.gov/technical/ps/2008-SPS-performance-standard.pdf Accessed 1 Oct 2016.
2. N Fallah, I Apostolopoulos, K Bekris, E Folmer, in Proceedings of the SIGCHI Conference on Human Factors in Computing Systems. CHI ’12. The user as a sensor: navigating users with visual impairments in indoor spaces using tactile landmarks (ACMNew York, 2012), pp. 425–432.
3. KM Varpe, MP Wankhade, Visually impaired assistive system. Int. J. Comput. Appl. 77(16), 5–10 (2013).
4. N Li, B Becerik-Gerber, Performance-based evaluation of RFID-based indoor location sensing solutions for the built environment. Adv. Eng. Inform.25(3), 535–546 (2011).
5. SM Jonas, E Sirazitdinova, J Lensen, D Kochanov, H Mayzek, T de Heus, R Houben, H Slijp, TM Deserno, Imago: image-guided navigation for visually impaired people. JAISE. 7(5), 679–692 (2015).