The OSTM/Jason-2 netCDF products added some attributes to their time variables
to handle a similar situation.
When declaring time as “seconds since a given epoch”, they also add an
attribute “tai_tuc_difference” which contains the number of leap seconds
applied since that epoch.
In addition, when the data is an array of time values, because a leap second
could conceivably be applied at a time within that array, there is also an
attribute "leap_second" that contains the UTC time at which any new leap second
is applied.
With this information, you have everything in the dataset to convert from UTC
to TAI.
An example from the Jason User Handbook:
double time(time);
time:long_name = "time (sec. since 2000-01-01)";
time:standard_name = "time";
time:units = "seconds since 2000-01-01 00:00:00.0";
time:calendar = "gregorian";
time:tai_utc_difference = [GA_TAI_UTC_DIF];
time:leap_second = [GA_LEAP_TIME];
time:comment = “ “tai_utc_difference” is the difference between TAI and
UTC reference time (seconds) for the first measurement of the data set.
“leap_second” is the UTC time at which a leap second occurs in the data
set, if any. After
this UTC time, the tai_utc_difference is increased by 1 second. ”
Regards,
Tim
__________________________________________________________________
From: CF-metadata [mailto:[email protected]] On Behalf Of Julien
Demaria
Sent: Thursday, April 23, 2015 2:51 PM
To: [email protected]
Subject: [CF-metadata] How to define time coordinate in GPS?
Hi,
I need to define a time coordinate variable which use the GPS time referential
instead of UTC, but I did not found how to specify this.
For the moment my variable look like this :
int64 time_stamp(rows) ;
time_stamp:standard_name = "time" ;
time_stamp:units = "microseconds since
2000-01-01 00:00:00" ;
time_stamp:_FillValue = -1L ;
Thanks in advance,
Julien
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