time_conversion.c File Reference

---

Detailed Description

GNSS core 'c' function library: converting time information.

Author:

Glenn D. MacGougan (GDM)

Date:

2007-11-29

Since:

2005-07-30

REFERENCES

• Hofmann-Wellenhof, B., H. Lichtenegger, and J. Collins (1994). GPS Theory and Practice, Third, revised edition. Springer-Verlag, Wien New York. pp. 38-42
  
• http://aa.usno.navy.mil/data/docs/JulianDate.html - Julian Date Converter
  
• http://aa.usno.navy.mil/faq/docs/UT.html
  
• http://wwwmacho.mcmaster.ca/JAVA/JD.html
  
• Raquet, J. F. (2002), GPS Receiver Design Lecture Notes. Geomatics Engineering, University of Calgary Graduate Course.
  

"LICENSE INFORMATION"
Copyright (c) 2007, refer to 'author' doxygen tags
All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided the following conditions are met:

• Redistributions of source code must retain te above copyright notice, this list of conditions and the following disclaimer.
  
• Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
  
• The name(s) of the contributor(s) may not be used to endorse or promote products derived from this software without specific prior written permission.
  

THIS SOFTWARE IS PROVIDED BY THE CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Definition in file time_conversion.c.

#include <sys/timeb.h>
#include <time.h>
#include <math.h>
#include "time_conversion.h"
#include "constants.h"

Go to the source code of this file.

Functions
BOOL	TIMECONV_GetSystemTime (unsigned short *utc_year, unsigned char *utc_month, unsigned char *utc_day, unsigned char *utc_hour, unsigned char *utc_minute, float *utc_seconds, unsigned char *utc_offset, double *julian_date, unsigned short *gps_week, double *gps_tow)
	Obtains the UTC time, GPS time, and Julian date from PC system time.
BOOL	TIMECONV_GetJulianDateFromGPSTime (const unsigned short gps_week, const double gps_tow, const unsigned char utc_offset, double *julian_date)
	Computes the Julian date from GPS time.
BOOL	TIMECONV_GetJulianDateFromUTCTime (const unsigned short utc_year, const unsigned char utc_month, const unsigned char utc_day, const unsigned char utc_hour, const unsigned char utc_minute, const float utc_seconds, double *julian_date)
	Computes the Julian date from UTC time.
BOOL	TIMECONV_GetGPSTimeFromJulianDate (const double julian_date, const unsigned char utc_offset, unsigned short *gps_week, double *gps_tow)
	Computes GPS time from the Julian date.
BOOL	TIMECONV_GetUTCTimeFromJulianDate (const double julian_date, unsigned short *utc_year, unsigned char *utc_month, unsigned char *utc_day, unsigned char *utc_hour, unsigned char *utc_minute, float *utc_seconds)
	Computes UTC time from the Julian date.
BOOL	TIMECONV_GetGPSTimeFromUTCTime (unsigned short utc_year, unsigned char utc_month, unsigned char utc_day, unsigned char utc_hour, unsigned char utc_minute, float utc_seconds, unsigned short *gps_week, double *gps_tow)
	Computes GPS time from UTC time.
BOOL	TIMECONV_GetGPSTimeFromRinexTime (unsigned short utc_year, unsigned char utc_month, unsigned char utc_day, unsigned char utc_hour, unsigned char utc_minute, float utc_seconds, unsigned short *gps_week, double *gps_tow)
	Computes GPS time from RINEX time. RINEX time looks like UTC but it is GPS time in year, month, day, hours, minutes, seconds.
BOOL	TIMECONV_GetUTCTimeFromGPSTime (unsigned short gps_week, double gps_tow, unsigned short *utc_year, unsigned char *utc_month, unsigned char *utc_day, unsigned char *utc_hour, unsigned char *utc_minute, float *utc_seconds)
	Computes UTC time from GPS time.
BOOL	TIMECONV_DetermineUTCOffset (double julian_date, unsigned char *utc_offset)
	This function is a look up table to determine the UTC offset from the Julian Date.
BOOL	TIMECONV_GetNumberOfDaysInMonth (const unsigned short year, const unsigned char month, unsigned char *days_in_month)
	Determines the number of days in a month, given the month and year.
BOOL	TIMECONV_IsALeapYear (const unsigned short year)
	Determines if the given year is a leap year.
BOOL	TIMECONV_GetDayOfYear (const unsigned short utc_year, const unsigned char utc_month, const unsigned char utc_day, unsigned short *dayofyear)
	Determines the day of year given the year, month, and day.
BOOL	TIMECONV_GetGPSTimeFromYearAndDayOfYear (const unsigned short year, const unsigned short dayofyear, unsigned short *gps_week, double *gps_tow)
	Determines the GPS time of the start of a day from the day of year and the year.

---

Function Documentation

BOOL TIMECONV_DetermineUTCOffset	(	double	julian_date,
		unsigned char *	utc_offset
	)

This function is a look up table to determine the UTC offset from the Julian Date.

Author:

Glenn D. MacGougan (GDM)

Date:

2007-11-29

Since:

2005-08-22

Returns:

TRUE(1) if successful, FALSE(0) otherwise.

Remarks:

• This function must be updated when the next UTC *utc_offset step occurs. Current max is (13).

REFERENCES

• Raquet, J. F. (2002), GPS Receiver Design Lecture Notes. Geomatics Engineering, University of Calgary Graduate Course.
  

"Offset Table"
UTCOffset, UTC Date, Julian Date [days]
0, Jan 06 1980 00:00:00.0, 2444244.5000
1, Jul 01 1981 00:00:00.0, 2444786.5000
2, Jul 01 1982 00:00:00.0, 2445151.5000
3, Jul 01 1983 00:00:00.0, 2445516.5000
4, Jul 01 1985 00:00:00.0, 2446247.5000
5, Jan 01 1988 00:00:00.0, 2447161.5000
6, Jan 01 1990 00:00:00.0, 2447892.5000
7, Jan 01 1991 00:00:00.0, 2448257.5000
8, Jul 01 1992 00:00:00.0, 2448804.5000
9, Jul 01 1993 00:00:00.0, 2449169.5000
10, Jul 01 1994 00:00:00.0, 2449534.5000
11, Jan 01 1996 00:00:00.0, 2450083.5000
12, Jul 01 1997 00:00:00.0, 2450630.5000
13, Jan 01 1999 00:00:00.0, 2451179.5000
14, Jan 01 2006 00:00:00.0, 2453736.5000

Parameters:

julian_date	Number of days since noon Universal Time Jan 1, 4713 BCE (Julian calendar) [days]
utc_offset	Integer seconds that GPS is ahead of UTC time, always positive [s], obtained from a look up table

Definition at line 500 of file time_conversion.c.

BOOL TIMECONV_GetDayOfYear	(	const unsigned short	utc_year,
		const unsigned char	utc_month,
		const unsigned char	utc_day,
		unsigned short *	dayofyear
	)

Determines the day of year given the year, month, and day.

Author:

Glenn D. MacGougan (GDM)

Date:

2007-11-29

Since:

2005-08-22

Returns:

TRUE(1) if successful, FALSE(0) otherwise.

Remarks:

(1) Performed independant comparison with http://www.mbari.org/staff/coletti/doytable.html

Definition at line 599 of file time_conversion.c.

BOOL TIMECONV_GetGPSTimeFromJulianDate	(	const double	julian_date,
		const unsigned char	utc_offset,
		unsigned short *	gps_week,
		double *	gps_tow
	)

Computes GPS time from the Julian date.

Author:

Glenn D. MacGougan (GDM)

Date:

2007-11-29

Since:

2005-08-22

Returns:

TRUE(1) if successful, FALSE(0) otherwise.

REFERENCES

• Hofmann-Wellenhof, B., H. Lichtenegger, and J. Collins (1994). GPS Theory and Practice, Third, revised edition. Springer-Verlag, Wien New York. pp. 38-42
  

Parameters:

julian_date	Number of days since noon Universal Time Jan 1, 4713 BCE (Julian calendar) [days]
utc_offset	Integer seconds that GPS is ahead of UTC time, always positive [s]
gps_week	GPS week (0-1024+) [week]
gps_tow	GPS time of week [s]

Definition at line 242 of file time_conversion.c.

BOOL TIMECONV_GetGPSTimeFromRinexTime	(	unsigned short	utc_year,
		unsigned char	utc_month,
		unsigned char	utc_day,
		unsigned char	utc_hour,
		unsigned char	utc_minute,
		float	utc_seconds,
		unsigned short *	gps_week,
		double *	gps_tow
	)

Computes GPS time from RINEX time. RINEX time looks like UTC but it is GPS time in year, month, day, hours, minutes, seconds.

Author:

Glenn D. MacGougan (GDM)

Date:

2007-12-07

Since:

2007-12-07

Returns:

TRUE(1) if successful, FALSE(0) otherwise.

Remarks:

• There is no UTC offset to apply
• The RINEX time system must be the GPS Time system to use this function.

REFERENCES

• Hofmann-Wellenhof, B., H. Lichtenegger, and J. Collins (1994). GPS Theory and Practice, Third, revised edition. Springer-Verlag, Wien New York. pp. 38-42
  
• RINEX version 2.11, (http://www.aiub-download.unibe.ch/rinex/rinex211.txt)

Parameters:

utc_year	Universal Time Coordinated [year]
utc_month	Universal Time Coordinated [1-12 months]
utc_day	Universal Time Coordinated [1-31 days]
utc_hour	Universal Time Coordinated [hours]
utc_minute	Universal Time Coordinated [minutes]
utc_seconds	Universal Time Coordinated [s]
gps_week	GPS week (0-1024+) [week]
gps_tow	GPS time of week (0-604800.0) [s]

Definition at line 405 of file time_conversion.c.

BOOL TIMECONV_GetGPSTimeFromUTCTime	(	unsigned short	utc_year,
		unsigned char	utc_month,
		unsigned char	utc_day,
		unsigned char	utc_hour,
		unsigned char	utc_minute,
		float	utc_seconds,
		unsigned short *	gps_week,
		double *	gps_tow
	)

Computes GPS time from UTC time.

Author:

Glenn D. MacGougan (GDM)

Date:

2007-11-29

Since:

2005-08-22

Returns:

TRUE(1) if successful, FALSE(0) otherwise.

Remarks:

(1) The utc offset is determined automatically from a look up table

REFERENCES

• Hofmann-Wellenhof, B., H. Lichtenegger, and J. Collins (1994). GPS Theory and Practice, Third, revised edition. Springer-Verlag, Wien New York. pp. 38-42
  

Parameters:

utc_year	Universal Time Coordinated [year]
utc_month	Universal Time Coordinated [1-12 months]
utc_day	Universal Time Coordinated [1-31 days]
utc_hour	Universal Time Coordinated [hours]
utc_minute	Universal Time Coordinated [minutes]
utc_seconds	Universal Time Coordinated [s]
gps_week	GPS week (0-1024+) [week]
gps_tow	GPS time of week (0-604800.0) [s]

Definition at line 357 of file time_conversion.c.

BOOL TIMECONV_GetGPSTimeFromYearAndDayOfYear	(	const unsigned short	year,
		const unsigned short	dayofyear,
		unsigned short *	gps_week,
		double *	gps_tow
	)

Determines the GPS time of the start of a day from the day of year and the year.

Author:

Glenn D. MacGougan (GDM)

Date:

2007-12-07

Since:

2007-12-07

Returns:

TRUE(1) if successful, FALSE(0) otherwise.

Parameters:

gps_week	GPS week (0-1024+) [week]
gps_tow	GPS time of week (0-604800.0) [s]

Definition at line 633 of file time_conversion.c.

BOOL TIMECONV_GetJulianDateFromGPSTime	(	const unsigned short	gps_week,
		const double	gps_tow,
		const unsigned char	utc_offset,
		double *	julian_date
	)

Computes the Julian date from GPS time.

Author:

Glenn D. MacGougan (GDM)

Date:

2007-11-29

Since:

2005-08-22

Returns:

TRUE(1) if successful, FALSE(0) otherwise.

REFERENCES

• Hofmann-Wellenhof, B., H. Lichtenegger, and J. Collins (1994). GPS Theory and Practice, Third, revised edition. Springer-Verlag, Wien New York. pp. 38-42
  

Parameters:

gps_week	GPS week (0-1024+) [week]
gps_tow	GPS time of week (0-604800.0) [s]
utc_offset	Integer seconds that GPS is ahead of UTC time, always positive [s]
julian_date	Number of days since noon Universal Time Jan 1, 4713 BCE (Julian calendar) [days]

Definition at line 190 of file time_conversion.c.

BOOL TIMECONV_GetJulianDateFromUTCTime	(	const unsigned short	utc_year,
		const unsigned char	utc_month,
		const unsigned char	utc_day,
		const unsigned char	utc_hour,
		const unsigned char	utc_minute,
		const float	utc_seconds,
		double *	julian_date
	)

Computes the Julian date from UTC time.

Author:

Glenn D. MacGougan (GDM)

Date:

2007-11-29

Since:

2005-08-22

Returns:

TRUE(1) if successful, FALSE(0) otherwise.

Remarks:

• Verified calculation using http://aa.usno.navy.mil/data/docs/JulianDate.html, a Julian Date Converter and http://wwwmacho.mcmaster.ca/JAVA/JD.html, another online converter tool.
  

REFERENCES

• Hofmann-Wellenhof, B., H. Lichtenegger, and J. Collins (1994). GPS Theory and Practice, Third, revised edition. Springer-Verlag, Wien New York. pp. 38-42
  

Parameters:

utc_year	Universal Time Coordinated [year]
utc_month	Universal Time Coordinated [1-12 months]
utc_day	Universal Time Coordinated [1-31 days]
utc_hour	Universal Time Coordinated [hours]
utc_minute	Universal Time Coordinated [minutes]
utc_seconds	Universal Time Coordinated [s]
julian_date	Number of days since noon Universal Time Jan 1, 4713 BCE (Julian calendar) [days]

Definition at line 206 of file time_conversion.c.

BOOL TIMECONV_GetNumberOfDaysInMonth	(	const unsigned short	year,
		const unsigned char	month,
		unsigned char *	days_in_month
	)

Determines the number of days in a month, given the month and year.

Author:

Glenn D. MacGougan (GDM)

Date:

2007-11-29

Since:

2005-08-22

Returns:

TRUE(1) if successful, FALSE(0) otherwise.

REFERENCES

• Hofmann-Wellenhof, B., H. Lichtenegger, and J. Collins (1994). GPS Theory and Practice, Third, revised edition. Springer-Verlag, Wien New York. pp. 38-42
  

Parameters:

year	Universal Time Coordinated [year]
month	Universal Time Coordinated [1-12 months]
days_in_month	Days in the specified month [1-28|29|30|31 days]

Definition at line 530 of file time_conversion.c.

BOOL TIMECONV_GetSystemTime	(	unsigned short *	utc_year,
		unsigned char *	utc_month,
		unsigned char *	utc_day,
		unsigned char *	utc_hour,
		unsigned char *	utc_minute,
		float *	utc_seconds,
		unsigned char *	utc_offset,
		double *	julian_date,
		unsigned short *	gps_week,
		double *	gps_tow
	)

Obtains the UTC time, GPS time, and Julian date from PC system time.

Author:

Glenn D. MacGougan (GDM)

Date:

2006-11-10

Since:

2005-08-22

Returns:

TRUE(1) if successful, FALSE(0) otherwise.

Remarks:

(1) Millisecond time is obtained

Parameters:

utc_year	Universal Time Coordinated [year]
utc_month	Universal Time Coordinated [1-12 months]
utc_day	Universal Time Coordinated [1-31 days]
utc_hour	Universal Time Coordinated [hours]
utc_minute	Universal Time Coordinated [minutes]
utc_seconds	Universal Time Coordinated [s]
utc_offset	Integer seconds that GPS is ahead of UTC time, always positive [s], obtained from a look up table
julian_date	Number of days since noon Universal Time Jan 1, 4713 BCE (Julian calendar) [days]
gps_week	GPS week (0-1024+) [week]
gps_tow	GPS time of week (0-604800.0) [s]

Definition at line 113 of file time_conversion.c.

BOOL TIMECONV_GetUTCTimeFromGPSTime	(	unsigned short	gps_week,
		double	gps_tow,
		unsigned short *	utc_year,
		unsigned char *	utc_month,
		unsigned char *	utc_day,
		unsigned char *	utc_hour,
		unsigned char *	utc_minute,
		float *	utc_seconds
	)

Computes UTC time from GPS time.

Author:

Glenn D. MacGougan (GDM)

Date:

2007-11-29

Since:

2005-08-22

Returns:

TRUE(1) if successful, FALSE(0) otherwise.

Remarks:

• The utc offset is determined automatically from a look up table

REFERENCES

• Hofmann-Wellenhof, B., H. Lichtenegger, and J. Collins (1994). GPS Theory and Practice, Third, revised edition. Springer-Verlag, Wien New York. pp. 38-42
  

Parameters:

gps_week	GPS week (0-1024+) [week]
gps_tow	GPS time of week (0-604800.0) [s]
utc_year	Universal Time Coordinated [year]
utc_month	Universal Time Coordinated [1-12 months]
utc_day	Universal Time Coordinated [1-31 days]
utc_hour	Universal Time Coordinated [hours]
utc_minute	Universal Time Coordinated [minutes]
utc_seconds	Universal Time Coordinated [s]

Definition at line 449 of file time_conversion.c.

BOOL TIMECONV_GetUTCTimeFromJulianDate	(	const double	julian_date,
		unsigned short *	utc_year,
		unsigned char *	utc_month,
		unsigned char *	utc_day,
		unsigned char *	utc_hour,
		unsigned char *	utc_minute,
		float *	utc_seconds
	)

Computes UTC time from the Julian date.

Author:

Glenn D. MacGougan (GDM)

Date:

2007-11-29

Since:

2005-08-22

Returns:

TRUE(1) if successful, FALSE(0) otherwise.

REFERENCES

• Hofmann-Wellenhof, B., H. Lichtenegger, and J. Collins (1994). GPS Theory and Practice, Third, revised edition. Springer-Verlag, Wien New York. pp. 38-42
  

Parameters:

julian_date	Number of days since noon Universal Time Jan 1, 4713 BCE (Julian calendar) [days]
utc_year	Universal Time Coordinated [year]
utc_month	Universal Time Coordinated [1-12 months]
utc_day	Universal Time Coordinated [1-31 days]
utc_hour	Universal Time Coordinated [hours]
utc_minute	Universal Time Coordinated [minutes]
utc_seconds	Universal Time Coordinated [s]

Definition at line 269 of file time_conversion.c.

BOOL TIMECONV_IsALeapYear

(

const unsigned short

year

)

Determines if the given year is a leap year.

Author:

Glenn D. MacGougan (GDM)

Date:

2007-11-29

Since:

2005-08-22

Returns:

TRUE(1) if the given year is a leap year, FALSE(0) otherwise

• Hofmann-Wellenhof, B., H. Lichtenegger, and J. Collins (1994). GPS Theory and Practice, Third, revised edition. Springer-Verlag, Wien New York. pp. 38-42
  

Definition at line 566 of file time_conversion.c.