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4 Operation
4.5 SPECIAL DATA INPUT COMMANDS
These entries are data messages that are generated by one MiLLennium-GLONASS GPSCard and sent to another
GPSCard or generated by a MiLLennium-GLONASS GPSCard and saved for later use by that MiLLennium-
GLONASS GPSCard (eg. $CALA). For example, consider a special configuration in which a MiLLennium-
GLONASS GPSCard #1 is able to send these data messages to a MiLLennium-GLONASS GPSCard #2 via a serial
port. For MiLLennium-GLONASS GPSCard #1, this is no different than sending these data messages to a file or
a screen. Each of these data messages has a special header which is interpreted by MiLLennium-GLONASS
GPSCard #2 to mean that the data in that message is to be used as an update of its own GLONASS parameters such
as time, position, velocity, acceleration or knowledge of satellite ephemeris.
In this general category also belong the RTCM data messages ($RTCMA, $RTCM3A, $RTCM9A, $RTCM16A,
$RTCM31, $RTCM34 and $RTCM59A). These are described in further detail in Chapter 4, Message Formats,
Page 33.
The injection of special command data can take place via COM1 or COM2. Remember, the source of these special
data commands are valid NovAtel ASCII data logs.
The special data input commands fall into three categories: Almanac Data, Differential Corrections and
Calibration Data. Listed below are input commands relevant to GLONASS. To see input commands that work
with GPS only, such as $REPA/B and $PVAA/B, please refer to the MiLLennium Command Descriptions Manual.
4.5.1 ALMANAC DATA
The MiLLennium-GLONASS GPSCard is capable of receiving and using both the GLONASS almanac and the
GPS almanac. The GLONASS almanac is stored in the log GALA (see Page 89) and the GPS almanac is stored in
the log ALMA (see Page 31). Please see the following sections for an explanation of both almanacs.
4.5.1.1 GPS Almanac VS GLONASS Almanac
The GPSCard's standard features include GPS and GLONASS almanac data collection. Following a cold-start
power-on or system reset, the GPSCard will begin a sky search. Once a valid satellite is acquired, the GPSCard
will begin downloading and decoding the almanac information. For a GPS satellite this process will take 12.5
minutes following a cold-start or reset (assuming there are no problems with satellite visibility or the antenna
system). It is noted that Ionospheric Correction Data and UTC data are also collected at the same time as almanac
data and will also be available following the 12.5 minutes collection period. The GLONASS almanac takes at least
5 minutes to download.
GPSCards with the SAVECONFIG option will automatically save almanacs in their non-volatile memory. They
will also automatically load the last saved almanac following a cold start or a reset. The card will save an almanac
and ionospheric and UTC data received from a satellite if there is no current data in non-volatile memory (NVM),
or if the GPS week number of the received data is newer than the week number of the data in NVM. The save will
occur for GPS almanacs from 12.5 - 25 minutes since the last reset, while for GLONASS satellites the save will
occur between 5 and 7.5 minutes afterwards. To check if almanac data is saved in the NVM of the GPSCard, check
Bit 16 for GPS and Bit 28 for GLONASS in the receiver status word. See Table H.2, Page 96, for more information.
There are no specific NovAtel log option commands to independently specify output of ionospheric or UTC
parameters. These parameters will always output following the GPS almanac $ALMA log and will be identified
by a $IONA and $UTCA header respectively. See Chapter 4, Page 31 for more information on the ALMA output
log command option. The GLONASS almanac is output as a $GALA log and is not followed by the ionospheric
($IONA) or UTC ($UTCA) information. See Chapter 4 (Page 32) and Appendix H (Page 89) for more information
on the $GALA log command option.
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GPS/GLONASS Receiver User Manual Rev 1
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