Sokkia Axis 3, Operation Manual

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Axis
3
Operation Chapter 4
Axis
3™
31
In Manual Tune Mode, you can specify the frequency or select
the beacon by name from the built-in global listing.
4.4.1 Using ABS Mode
Using ABS, the Axis
3
receiver selects and tunes to the most
appropriate beacon without operator intervention. The Axis
3
operates in ABS mode by default and uses its two independent
channels to identify and lock to DGPS beacons without
interrupting the continuous flow of RTCM data to your GPS
receiver.
ABS mode is ideal for navigation applications over
considerable areas, eliminating the need for operator
intervention when switching from one beacon coverage zone to
another.
4.4.1.1 ABS Global Search
When powered for the first time, the Axis
3
receiver initiates a
Global Search, examining each available DGPS beacon
frequency, and recording Signal Strength (SS) measurements.
The receiver uses these measured values to compute an average
SS, and noise floor to sort the frequencies in descending order
of SS. The two channels cooperatively examine the frequencies
with the highest SS measurements above the computed noise
floor to determine the station providing the strongest RTCM
signal. The receiver’s primary channel locks to the first
identified DGPS broadcast, while the second channel continues
searching in the background for superior beacon signals. If no
signal is available, the Axis
3
receiver will initiate a fresh Global
Search, continuing this cycle until it finds a valid beacon.
4.4.1.2 ABS Background Search
During the Background Search, the second channel examines
all frequencies at both the 100 and 200 bps Minimum Shift
Keying (MKS) bit rates to identify beacons possessing superior