Trimble Outdoors SK8 - Manual (Page 87)

Lassen-SK8 Embedded GPS Module A-23
Trimble Standard Interface Protocol
A.17.12 Command Packet 0x2B
This packet provides the GPS receiver with an approximate initial position in latitude and
longitude coordinates (WGS-84). This packet is useful if the user has moved more than
1,000 miles after the previous fix. (Note that 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. To initialize with
ELEF position, use Command Packet
0x 23. The data format is shown inTable A-19:
A.17.13 Command Packet 0x2D
This packet requests the calculated offset of the GPS receiver master oscillator. This
packet contains no data. The GPS receiver returns Packet
0x 4D. This packet is used
mainly for service. The permissible oscillator offset varies with the particular GPS
receiver unit.
A.17.14 Command Packet 0x2E
This packet provides the approximate GPS time of week and the week number to the GPS
receiver. The GPS receiver returns Packet
0x 4E. The data format is shown below. The
GPS week number reference is Week # 0 starting January 6, 1980. The seconds count
begins at the midnight which begins each Sunday morning. This packet is usually not
required when the battery back-up voltage is applied as the internal clock keeps time to
sufficient accuracy. This packet is ignored if the receiver has already calculated the time
from tracking a GPS satellite.
*
Note – See A.17.22, Report Packet 41 for information on the Extended GPS week
number.
Table A-19. Command Packet 0x23 Data Format
Byte Item Type Units
0-3 Latitude Single Radians, north
4-7 Longitude Single Radians, east
8-11 Altitude Single Meters
Table A-20. Command Packet 0x2E Data Formats
Byte Item Type Units
0-3 GPS time of week Single Seconds
4-5 Extended GPS week
number Integer Weeks