Dear all,
I think "3 days since 1970-01-01" is a sensible statement, with "3"
being the number and "days since 1970-01-01" being the units. Would
anybody normally interpret "5 3 days since 1970-01-01" as meaning "15
days since 1970-01-01"? If not, then I don't think we should allow a
unit of "3 days since 1970-01-01". This would be just as confusing as
allowing a unit of "3 meters" and interpreting "5 3 meters" as "15
meters". Since we don't allow "3 meters" as a unit, why should we allow
"3 days since 1970-01-01" as a unit?
Best regards,
Karl
On 3/26/11 6:46 AM, Don Murray wrote:
John-
On 3/25/11 4:54 PM, John Caron wrote:
On 3/22/2011 6:53 AM, John Caron wrote:
Consider:
int time(sample=1001);
:long_name = "Measurement time";
:standard_name = "time";
:units = "days since 1970-01-01";
vs
int time(sample=1001);
:long_name = "Measurement time";
:standard_name = "time";
:units = "3 days since 1970-01-01";
values = 1, 2, 3, ...
are these equivalent or does the second one mean every 3 days ? Is the
second one illegal ?
Im am going to assume that the second form is illegal, that is, you may
not have a number in front of the unit in a "time coordinate unit" (CF
section 4.4)
I agree with Beno that it should be legal. GrADS gives their units in
terms of N (minutes, hours, days, months, years) from a reference time.
When I wrote the GrADS IOSP, I originally was using this syntax,
because then your time coordinate values are 0,1,2,..... However, 3mo
intervals came up with the problems that you have shown here, so I
converted everything to hours since the base date. But, if we had a
library that would compute 3mo since 2011-04-01 as 2011-07-01, I would
revert to that syntax because it is closer to the original GrADS definition.
Don
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