Trimble Outdoors Part Number 45005-00-ENG 0x20 0x21 0x23, Almanac Request, Current Time Request

Trimble Standard Interface Protocol A

0x20

0x21

0x23

!

Command Packet 20

Almanac Request

This packet requests almanac data for one satellite from the GPS receiver. This packet contains one data byte specifying the satellite PRN number. The GPS receiver returns packet 40 hex.

Command Packet 21

Current Time Request

This packet requests current GPS time. This packet contains no data. The GPS receiver returns packet 41 hex.

Command Packet 23

Initial Position (XYZ Cartesian ECEF) Command

This packet provides the GPS receiver with an approximate initial position in XYZ coordinates. This packet is useful if the user has moved more than about 1,000 miles since the previous fix.

Note – The GPS receiver can initialize itself without any data from the user; this packet merely reduces the time required for initialization.

This packet is ignored if the receiver is already calculating positions.

The origin is the earth’s center. The X-axis points toward the intersection of the equator and the Greenwich meridian, the Y-axis points toward the intersection of the equator and the 90o meridian, and the Z-axis points toward the North Pole. The cold-start default LLA (not XYZ) position is 0, 0, 0.

The data format is shown in the table below.

Table A-19 Command Packet 23

Byte	Item	Type	Units
0-3	X	Single	meters

A-22 Acutime 2000 Synchronization Kit User Guide