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A-34 Lassen-SK8 Embedded GPS Module
Trimble Standard Interface Protocol
A.17.30 Main 0x4A Report Packet Type
The data format is shown below:
The LLA conversion is done according to the datum selected using Packet 0x8E-15. The
default is WGS-84. Altitude is referred to the datum ellipsoid or the MSL Geoid,
depending on which I/O “LLA altitude” option is selected. The time-of-fix is in GPS time
or UTC, depending on which I/O “timing” option is selected.
This packet also is sent at start-up with a negative time-of-fix to report the current known
position. Packet 0x84 provides a double-precision version of this information
I
Caution – When converting from radians to degrees, significant and readily visible errors will be
introduced by use of an insufficiently precise approximation for the constant PI. The value of the
constant PI as specified in ICD-GPS-200 is 3.1415926535898.
A.17.31 Second 0x4A Packet Type
Report Packet 0x4A is also sent in response to the setting or requesting of the Reference
Altitude Parameters using Command Packet 0x2A. These parameters can be used in the
Manual 2-D mode.
Reference Altitude
The altitude used for manual 2-D positions if the altitude flag is set. Altitude is in units of
HAE WGS-84 or MSL depending on the selected I/O options for the position.
Table A-33. Report Packet 0x4A Data Formats
Byte Item Type Units
0-3 Latitude SINGLE radians; + for north, - for south
4-7 Longitude SINGLE radians; + for east, - for west
8-11 Altitude SINGLE meters (HAE or MSL)
2-15 Clock Bias SINGLE meters
6-19 Time-of-Fix SINGLE seconds (GPS or UTZ)