3. Even: yes, I'm not quite sure whether this should be handled on
GDAL or TIFF level. Other GDAL-readable format like netcdf-cf have
time standards already, but yes, geotiffs (and lately COGs =
cloud-optimized geotiffs <https://www.cogeo.org/>) are the lingua
franca of our community. Setting GDAL fields START_DATE and END_DATE
indeed feels like a good solution, so I wanted to find out how to do
this properly in the hope of creating a standard.
It could certainly be good to have a standard for such metadata items
for TIFF that apply in the Earth Observation domain, and would be the
equivalent of netcdf-cf conventions, or maybe porting fields from STAC
(https://stacspec.org/). Unfortunately the TIFF tag mechanism is hard to
make evolve given that it implies a registry to attribute a code for a
tag/key and an entity that takes care of doing that, which no longer
happens those past years. Hence my suggestion to have that at the GDAL
level. There's also the
https://www.awaresystems.be/imaging/tiff/tifftags/geo_metadata.html tag
used by the DGIWG community, to put XML ISO metadata in it, but that's
going into complex metadata system.
On Thu, May 12, 2022 at 12:46 PM Bob Friesenhahn
<[email protected]> wrote:
On Thu, 12 May 2022, Simon (Vsevolod) Ilyushchenko wrote:
>
>>
>> Can you assume DateTime is UTC with your particular files and
use cases?
>>
>
> Yes, this is a good fallback option.
I am not sure about established precedence, but this is much better
than being a mere fallback option as long as the recipient knows
it is
UTC. This could be handled via documentation.
Dealing with time zones is hard, and it assumes that both the writer
and the reader have knowledge of the current time zone, and access to
the time zone database necessary to do conversions.
It may still be necessary for the writer and reader do to something
special to produce and consume UTC timestamps.
Unix type systems (and those using NTP) have a system clock which is
on UTC time.
Bob
--
Bob Friesenhahn
[email protected],
http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/
<http://www.GraphicsMagick.org/>
Public Key, http://www.simplesystems.org/users/bfriesen/public-key.txt
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