Leica GR30 - Background Information on External Oscillators; SBAS Note

6: Context sensitive help
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the external oscillator and switch to the external oscillator when available. If the
external oscillator is still not available when this button is pressed, a message will be
shown in the event log and the receiver will continue to use the internal oscillator.
This is a single fallback after 5 minutes without automatic return
to external oscillator.
The fallback to internal oscillator will also occur when the
antenna is disconnected for more than 5 minutes.
Frequency
Select the frequency at which the external oscillator is set to work.
Process noise element h
0
, h
-
1
and h
-2
Only available when using an H-maser external oscillator.
Set the values for the 3 process noise elements of the linear portion of the clock model.
There are the h
0
, h
-1
and h
-2
elements of the power law spectral density model used to
describe the frequency noise characteristics of an oscillator.
Restore default values
Press to restore the default values.
The restore default button fills all fields with the default values
and stores these values. Pressing the save button is not
necessary. When accepting the confirmation message, all
settings on this page are overwritten with the default settings.
Initialize measurement
engine
This button redirects you to the Tools page where you can re-initialize the
measurement engine. Then all ephemeris and almanac data will be deleted and the
position computation will be restarted.
SBAS note
For SBAS logging, the following behaviour will be seen:
Event log shows a complete loss of lock message when no SBAS data is tracked.
MDB and RINEX logging will always log the current SBAS observations when activated.
NMEA position output shows the following
Description
SBAS is off
Navigated position.
SBAS use for DGPS is on
Differential code position.
SBAS use for DGPS satellite is lost
Last position before SBAS data was lost for 60s then reset to navigated position.
SBAS use for DGPS satellite
become available
Differential code position.
Background information on external oscillators
An unsteered oscillator can be approximated by a three-state clock model, with two states representing the range bias and range bias
rate, and a third state assumed to be a Gauss-Markov (GM) process representing the range bias error generated from satellite clock
dither. The third state is included because the Kalman filter assumes an (unmodeled) white input error. The significant correlated errors
produced by satellite clock dither are obviously not white and the Markov process is an attempt to handle this kind of short term
variation.