u-blox 6

accuracy. As the position error translates into a time error when using Time Mode (see above), one should
carefully evaluate the time accuracy requirements and the choose an appropriate position accuracy
requirement.
Survey-in ends, when both requirements are met. After Survey-in has finished successfully, the receiver will
automatically enter fixed position Time Mode. The Survey-in status can queried using the UBX-TIM-SVIN
message.
The "Standard Deviation" parameter defines uncertainty of the manually provided "True Position"
set of parameters. This uncertainty directly affects the accuracy of the timepulse. This is to prevent
an error that would otherwise be present in the timepulse because of the initially inaccurate
position (assumed to be correct by the receiver) without users being aware of it. The "3D accuracy"
parameter in "Fixed Position" as well as the "Position accuracy limit" in "Survey-in" affect the
produced time information and the timepulse in the same way. Please note that the availability of
the position accuracy does not mitigate the error in the timepulse but only accounts for it when
calculating the resulting time accuracy.
11 Timepulse
u-blox GPS receivers include a Timepulse function providing clock pulses with configurable duration and
frequency. The UBX-TIM-TP message provides time information for the next pulse, time source and the
quantization error of the output pin.
11.1 Recommendations
• For best timepulse performance it is recommended to disable the SBAS subsystem.
• When using Timepulse for Precision Timing applications it is recommended to calibrate the RF signal delay
against a reference-timing source.
• Care needs to be given to the Cable Delay settings in the receiver configuration.
• In order to get the best timing accuracy with the antenna, a fixed and accurate position is needed. Once the
receiver is in timing mode, the dynamic model does not influence the timing accuracy.
GPS.G6-SW-10018-A Public Release Page 26 of 201