...Due to GPS vulnerabilities...... GPS is vulnerable to jamming or spoofing. GPS is now so interwoven into things we take for granted that---shut-down GPS and you can bring an entire city to a standstill. Read the article:
Why GPS is more vulnerable than ever
http://www.csmonitor.com/World/Passcode/2016/0510/Why-GPS-is-more-vulnerable-than-ever
Why GPS is more vulnerable than ever
http://www.csmonitor.com/World/Passcode/2016/0510/Why-GPS-is-more-vulnerable-than-ever