Meinberg LANTIME M600 Technical Information download pdf (Page 16)

The high precision orbit parameters of a satellite are called ephemeris parameters

whereas a reduced precision subset of the ephemeris parameters is called a satellite’s

almanac. While ephemeris parameters must be evaluated to compute the receiver’s

position and clock offset, almanac parameters are used to check which satellites are in

view from a given receiver position at a given time. Each satellite transmits its own

set of ephemeris parameters and almanac parameters of all existing satellites.

GPS170 Features

The hardware of GPS170 is a 100 mm x 160 mm microprocessor board. The front

panel integrates a 2 x 40 character LC display, two LED indicators and 5 push

buttons. The receiver is connected to the antenna/converter unit by a 50 Ω coaxial

cable (refer to "Mounting the Antenna"). Feeding the antenna/converter occurs DC

insulated via the antenna cable. Optionally an antenna splitter for up to four receivers

connected to one antenna is available.

The navigation message coming in from the satellites is decoded by GPS170´s

microprocessor in order to track the GPS system time with an accuracy of better than

500 ns or 250 ns (OCXO). Compensation of the RF signal’s propagation delay is

done by automatic determination of the receiver’s position on the globe. A correction

value computed from the satellites´ navigation messages increases the accuracy of the

board’s TCXO or OCXO to 10

-9

and automatically compensates the oscillators aging.

The last recent value is restored from the battery buffered memory at power-up.

Time Zone and Daylight Saving

GPS system time differs from the universal time scale (UTC) by the number of leap

seconds which have been inserted into the UTC time scale after GPS had been

initiated in 1980. The current number of leap seconds is part of the navigation

message supplied by the satellites, so GPS170´s internal real time is based on UTC.

Conversion to local time including handling of daylight saving year by year can be

done by the receiver’s microprocessor if the corresponding parameters are set up by

the GPS Monitor (included Windows software).

Internally LANTIME always runs on UTC based time. NTP calculates this UTC time

from the GPS receivers local time. The time zone of LANTIME is fixed to UTC.

However, the time monitored on the LC display is the GPS receiver's local time.

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Meinberg LANTIME M600 Technical Information Page 16