Trimble Standard Interface Protocol

A

"Caution – GPS week numbers run from 0 to 1023 and then cycles back to week #0. Week #0 began January 6, 1980. Another week #0 began August 22, 1999. The receiver automatically adds 1024 to the GPS week number after August 21, 1999, and reports the cumulative week number.

The seconds count begins with "0" each Sunday morning at midnight GPS time. A negative indicated time-of-week indicates that time is not yet known; in that case, the packet is sent only on request. The following table shows the relationship between the information in packet 41, and the packet 46 status code.

Table A-31 Relationship Between Packet 41 and Packet 46

Approximate Time

Time Source

Sign

Packet 0x46

Accuracy

 

(TOW)

Status Code

None

No time at all

0x01

 

 

 

 

Unknown

Approximate time from

+

0x01

 

real-time clock or packet 2E

 

 

20 to 50 msec + clock

Time from satellite

+

not 0x01

drift

 

 

 

Full accuracy

Time from GPS solution

+

0x00

 

 

 

 

!Note – Before using the GPS time, verify that the packet 46 status code is 0x00 ("Doing position fixes"). This ensures the most accurate GPS time.

A-42

Acutime 2000 Synchronization Kit User Guide

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Trimble Outdoors Part Number 45005-00-ENG manual Table A-31 Relationship Between Packet 41 and Packet, Status Code