SERTEL T-GPS-300, Operation Manual

Page: 7 / 132

1
01 INTRODUCTION
:
Global Positioning System is an absolute system to provide continuously the
following to unlimited users.
3 dimensional Position Fixing (Latitude; Longitude & Altitude).
Velocity ( Speed/Course ) measurement by detecting the Doppler shift in the radio
signals emitted by GPS Satellites.
Time Reference generation, utilizing the fact that the system is operated on a common
precise time base.
GPS provides continuous worldwide coverage, 24 hours a day under
Weather conditions
Satellites distributed in 6 orbital planes (4 in each plane) spaced around the
equator, pass over the earth at an altitude of approximately 20,000 kilometers.
Each satellite has an orbital period of 12 side real hours (11 Hrs. and 58 Mnts. of civil
time). A single satellite will orbit the earth twice a day, tracing the exact foot print
path; but passing 4 minutes earlier than the day before. This ensures that at least 4
satellites will be in view at any time above any point on earth. Each GPS satellite
bears an ultimate precision clock utilizing Rubidium-Cesium oscillation whose accuracy
is comparable to Inter national Atomic Time.
GPS Receiver collects the data from GPS Satellites and out puts a time base
pulse (1PPS) every second in precise synchronisation with UTC/IST. Each 1PPS Pulse
is accompanied by a Serial Data packet output ( A real time data comprising of Year,
Month, Date, Hour, Minute and Second), which is a time stamp for that pulse. This
output is utilised by Master Clock to synchronise its time with UTC/IST with a
maximum uncertainity of 1 micro second and generate various outputs to
synchronise any number of digital clock /microprocessor based systems.
GPS system is sponsored and operated by US Department of Defence. Civilian
access to the system is guaranteed through an agreement between US DOD and US
DOT (Dept. of Transportation) and is subject to US Govt. Selective Availability
(SA) policy
The Global Positioning system (GPS) is operated by the U.S.DOT and is subject
to U.S. Government selective availability (SA) Policy. SERTEL is not liable for the
degradation by SA Users are expected to be familiar with system and make . Full
use of it with their own responsibility.
SERTEL Electronics Pvt. Ltd reserves the right to make changes to our products any
specifications without notice.