This is an article on making a network attached Stratum 1 NTP Server using a Raspberry Pi+ Model 2 or 3 and the Uputronics Raspberry Pi+ GPS Expansion Board. If you need a standalone ready to go solution or need more performance please consider the LeoNTP Networked Time server unit which is available hereThis solution will not give you a standalone off grid NTP server. NTP isn’t designed to work off grid using just the NMEA derived time and PPS to discipline it. You need an external server and then use PPS to discipline it.