On 3/14/2011 9:40 PM, Dave Allured wrote:
There are several existing solutions to your question, depending on
the constraints or requirements of your application. Some of these
use encodings that are not supported by Udunits, but are explicitly
legal under the current version of CF. Here are two leading solutions:
1. time@units = "days since 1930-01-01"
+ time@calendar = "gregorian"
* Compatible with current CF conventions
* Compatible with Udunits-1 and -2
* Compatible with many existing general purpose softwares
* Conforms to the "western world's" actual historic calendar
* Complies with CF and COARDS precautions to AVOID fuzzy
. units of months or years
* Numeric time step is NOT constant for increments of
. months or years
2. time@units = "months (or years) since 1930-01-01"
+ time@calendar = "360_day"
* Compatible with current CF conventions
* NOT compatible with Udunits-1 or -2
* Compatible with SOME existing general purpose softwares
* DOES NOT conform to the "western world's" actual historic calendar
* DOES NOT comply with CF and COARDS precautions to AVOID fuzzy
. units of months or years, but reasonable in this context
* Numeric time step IS constant for increments of
. months or years
So, what constraints are important for you, and will either of the
above solutions be satisfactory?
--Dave A.
NOAA/PSD/CIRES
Hi Dave:
option 1 is suboptimal because one has to calculate the days correctly.
Also it makes the time coordinates not human readable, eg:
time:units = "days since 1850-01-01";
values: 0, 365, 730, 1096, 1461, 1826, 2191, 2557, 2922, 3287, 3652,
4018, 4383, 4748, 5113, 5479, 5844, 6209, 6574, 6940, 7305, 7670, 8035,
8401, 8766, 9131, 9496, 9862, 10227, 10592, 10957, 11323, 11688, 12053,
12418, 12784, 13149, 13514, 13879, 14245, 14610, 14975, 15340, 15706,
16071, 16436, 16801, 17167, 17532, 17897, 18262, 18627, 18992, 19357,
19722, 20088, 20453, 20818, 21183, 21549, 21914, 22279, 22644, 23010,
23375, 23740, 24105, 24471, 24836, 25201, 25566, 25932, 26297, 26662,
27027, 27393, 27758, 28123, 28488, 28854, 29219, 29584, 29949, 30315,
30680, 31045, 31410, 31776, 32141, 32506, 32871, 33237, 33602, 33967,
34332, 34698, 35063, 35428, 35793, 36159;
vs
time:units = "years since 1850-01-01";
values: 0, 1, 2, 3 etc;
option 2, i am working on adding non-standard calenders to the CDM, so I
will look at that closer.
thanks
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