GPS UTC correction parameters. More...

#include <gpsdefs.h>

Data Fields
CSUM	csum
	Checksum of the remaining bytes. More...

int16_t	valid
	Flag indicating UTC parameters are valid. More...

T_GPS	t0t
	Reference Time UTC Parameters [wn\|sec]. More...

double	A0
	+- Clock Correction Coefficient 0 [sec] More...

double	A1
	+- Clock Correction Coefficient 1 [sec/sec] More...

uint16_t	WNlsf
	Week number of nearest leap second. More...

int16_t	DNt
	The day number at the end of which a leap second occurs. More...

int8_t	delta_tls
	Current UTC offset to GPS system time [sec]. More...

int8_t	delta_tlsf
	Future UTC offset to GPS system time after next leap second transition [sec]. More...

Detailed Description

GPS UTC correction parameters.

UTC correction parameters basically as sent by the GPS satellites.

The csum field is only used by the card's firmware to check the consistency of the structure in non-volatile memory.

The field labeled valid indicates if the parameter set is valid, i.e. if it contains data received from the satellites.

t0t, A0 and A1 contain fractional correction parameters for the current GPS-UTC time offset in addition to the whole seconds. This is evaluated by the receivers' firmware to convert GPS time to UTC time.

The delta_tls field contains the current full seconds offset between GPS time and UTC, which corresponds to the number of leap seconds inserted into the UTC time scale since GPS was put into operation in January 1980.

delta_tlfs holds the number of "future" leap seconds, i.e. the UTC offset after the next leap second event defined by WNlsf and DNt.

The fields WNlsf and DNt specify the GPS week number and the day number in that week for the end of which a leap second has been scheduled.

Note: : The satellites transmit WNlsf only as a signed 8 bit value, so it can only define a point in time which is +/- 127 weeks off the current time. The firmware tries to expand this based on the current week number, but the result is ambiguous if the leap second occurs or occurred more than 127 weeks in the future or past.

So the leap second date should only be evaluated and displayed in a user interface if the fields delta_tls and delta_tlsf have different values, in which case there is indeed a leap second announcement inside the +/- 127 week range.

Definition at line 18564 of file gpsdefs.h.