u-blox 6

5.4 Receiver Default Configuration
Permanent Configurations can be reset to Default Configurations through a UBX-CFG-CFG/clear message. The
receiver's Default Configuration is determined at system startup. Refer to specific product data sheet for further
details.
6 NMEA Protocol Configuration
The NMEA protocol on u-blox receivers can be configured to the need of customer applications using
CFG-NMEA. As default all invalid positions out of the defined accuracy range are not reported.
There are two NMEA standards supported. The default NMEA protocol version is 2.3. Alternatively also
Specification version 2.1 can be enabled (for details on how this affect the output refer to section Position Fix
Flags in NMEA Mode ).
NMEA filtering flags
Parameter
Position filtering
Masked position
filtering
Time filtering
Date filtering
SBAS filtering
Track filtering
Description
If disabled, invalid or old position output is being communicated, but the valid flag
indicates that the data is not current.
If disabled, Masked position data is still being output, but the valid flag will indicate that
the defined accuracy range has been exceeded.
If disabled, the receiver's best knowledge of time is output, even though it might be
wrong.
If disabled, the receiver's best knowledge of date is output, even though it might be
wrong.
If enabled, SBAS satellites are reported according to the NMEA standard.
If disabled, an unfiltered course over ground (COG) output is being output.
NMEA flags
Parameter
Compatibility Mode
Consideration Mode
Description
Some NMEA applications only work with a fixed number of digits behind the decimal
comma. Therefore u-blox receivers offer a compatibility mode to communicate with the
most popular map applications.
u-blox receivers use a sophisticated signal quality detection scheme, in order to produce
the best possible position output. This algorithm considers all SV measurements, and
eventually decides to only use a subset thereof, if it improves the overall position
accuracy. If Consideration mode is enabled, all Satellites, which were considered for
navigation, are being communicated as being used for the position determination. If
Consideration Mode is disabled, only those satellites are marked as being used, which
after the consideration step remained in the position output.
7 Forcing a Receiver Reset
Typically, in GPS receivers, one distinguishes between Cold, Warm, and Hot starts, depending on the type of
valid information the receiver has at the time of the restart.
• Cold start In this mode, the receiver has no information from the last position (e.g. time, velocity, frequency
etc.) at startup. Therefore, the receiver must search the full time and frequency space, and all possible
satellite numbers. If a satellite signal is found, it is tracked to decode the ephemeris (18-36 seconds under
strong signal conditions), whereas the other channels continue to search satellites. Once there is a sufficient
number of satellites with valid ephemeris, the receiver can calculate position- and velocity data. Please note
that some competitors call this startup mode Factory Startup.
GPS.G6-SW-10018-A Public Release Page 16 of 201