Trimble Outdoors 45005-00-ENG Manuel d'utilisateur télécharger pdf (Page 52)

5-4 Acutime 2000 Synchronization Kit User Guide

System Operation

5.2.2 Tracking Modes

The Acutime 2000 operates in one of two main fix modes:

• Self-Survey (Position fix mode)

• Overdetermined Clock mode

After establishing a reference position in Self-Survey mode, the

Acutime 2000 automatically switches to Overdetermined (OD) Clock

mode.

Self-Survey Mode

At power-on, the Acutime 2000 performs a self-survey by averaging

2000 position fixes. The number of position fixes until survey

completion is configurable using the 8E-4B or 8E-A9 command.

The default mode during self-survey is 3-D manual, where the

receiver must obtain a 3-D solution with a PDOP below both the

PDOP mask and PDOP switch. The PDOP mask and switch criteria

can be set and queried using a TSIP packet. If fewer than four

conforming satellites are visible, the Acutime 2000 suspends data

output.

The highest accuracy fix mode is 3-D manual, where altitude is

always calculated along with the latitude, longitude, and time.

Obtaining a position requires four satellites with a PDOP below the

PDOP mask. Depending on how the PDOP mask is set, 3-D mode can

be restrictive when the receiver is subjected to frequent obscuration

or when the geometry is poor due to an incomplete constellation.

If only a 2-D solution is desired, or if the exact altitude is known, 2-D

manual should be requested. In this case, the receiver uses either the

last altitude obtained in a 3-D fix, or the altitude supplied by the user.

Any error in the assumed altitude affects the accuracy of the latitude

and longitude solution. Use packet BB to set the desired position

fix mode.

Note – Altitude and the fix mode are stored in non-volatile memory.

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Trimble Outdoors 45005-00-ENG Manuel d'utilisateur Page 52