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4.3 Data Logging
In applications where the GPS receiver reported position, velocity, and time needs to be
logged, the TISTAR25 supports logging capability directly by storing the data in the on-board
memory. The logged data may be retrieved later.
The logged information consists of:
! GPS time (WNO, TOW), with 1 second resolution.
! Position in ECEF coordinate, with 1 meter resolution.
! Velocity, with 1 meter/sec resolution.
! Navigation mode (2D, 3D).
! DGPS used indicator
All data logging commands and each logged data output is sent with message header,
message body, and message footer protocol as described in section 4.2.
The TISTAR25 can log up to 5000 sets of data.
4.3.1 Data Logging Input Messages
4.3.1.1 LogConfig Set
This command configures the logging function.
Byte # Contents Range Size Unit
1 Message ID = 0x81 Unsigned byte
2 Command LogConfig = 0x10 Unsigned byte
3 ~ 4 Configuration
1 = enable data logging
0 = disable data logging
Unsigned 16bit integer
5 ~ 6 delta_Tmin 0 ~ 65535 Unsigned 16bit integer sec
7 ~ 8 delta_Tmax 0 ~ 65535 Unsigned 16bit integer sec
9 ~ 10 delta_D 0 ~ 65535 Unsigned 16bit integer meter
The data logging function stores receiver position, velocity, time and status information
according to the following algorithm:
delta_Tmin : Time interval to check if data logging is required; must be > 0.
delta_Tmax : Maximum time interval beyond which data must be logged.
delta_D : Maximum distance beyond which data must be logged.
distance = current_position – last_logged_position
elapsed_time = current_time – last_logged_time
if ((elapsed_time < (delta_Tmin - 1)) or (delta_Tmin == 0)) return and do not record PVT data
if ( ((elapsed_time > (delta_Tmax - 1)) and (delta_Tmax > 0))
or ((distance > (delta_D - 1)) and (delta_D > 0) )) record PVT data