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ALAS5 Hardware Interface Overview
3 GNSS Interface
32
ALAS5_HIO_v00.030a 2019-04-01
Confidential / Preliminary
Page 32 of 50
3 GNSS Interface
ALAS5 integrates a GNSS receiver that offers the full performance of GPS/GLONASS technol-
ogy. The GNSS receiver is able to continuously track all satellites in view, thus providing accu-
rate satellite position data.
The integrated GNSS receiver supports the NMEA protocol via USB or ASC0 interface. NMEA
is a combined electrical and data specification for communication between various (marine)
electronic devices including GNSS receivers. It has been defined and controlled by the US
based National Marine Electronics Association. For more information on the NMEA Standard
please refer to http://www.nmea.org.
Depending on the receiver’s knowledge of last position, current time and ephemeris data, the
receiver’s startup time (i.e., TTFF = Time-To-First-Fix) may vary: If the receiver has no knowl-
edge of its last position or time, a startup takes considerably longer than if the receiver has still
knowledge of its last position, time and almanac or has still access to valid ephemeris data and
the precise time.
By default, the GNSS receiver is switched off. It has to be switched on and configured.
Dead Reckoning Sync Line:
Dead reckoning solutions are used in (automotive) platforms to determine the (vehicles) loca-
tion even when there is no GPS signal available (e.g. in tunnels, basement garages or even
between high buildings in cities).
In addition to dead reckoning related NMEA sentences, ALAS5 provides a dead reckoning syn-
chronization line (DR_SYNC line) to be employed in external dead reckoning applications.
DR_SYNC is derived from the GNSS signal clock as 1 pulse per second (1PPS) signal. The
DR_SYNC signal is provided as long as synchronized with the GNSS satellite clock, and con-
tinues after GNSS signal loss.
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