[CF-metadata] fixed sensors, depth, datum

From: Dale Robinson <dhr.sfsu>
Date: Fri, 12 Sep 2008 14:13:01 -0700

Hi Ethan and anybody else,

I guess we are getting to the core of this discussion, at least in terms
of whether or not my further involvement is needed.

The question for me is, does or will the CF convention allow some method
to include offsets between tidal datums, or allow some other means for a
user to convert among z referenced to different datums?

Your answer below suggests that the CF convention is not the place for
this information... that the information is out there and it is up to
the user to find it.

Please let me know if I've got that right.

Cheers.

-Dale

-----------------------------
> 3) ?The fact the Dale wants to distinguish the various tidal datums
> shows that they define distinct quantities.?
>
> When I think about it, yes they seem to be distinct quantities. The
> range of mean lower low water and mean higher high water varies from
> location to location. A user of the data may not know what the offsets
> among datums are in a particular area. Heights referenced to these
> datums (especially MLLW) are very important to local users of the
> data. As a user of the CF convention and netCDF, I want to make sure
> that the people using my data can convert the height values we give
> them into values most useful to them. So inclusion of an offset
> variable, especially one so intuitively named
> (altitude_of_mean_low_water) would help me and many of the users of my
> data immensely.

Even if the user doesn't know the offsets between two tidal datums, they
do exist. To me, that doesn't seem like enough of a difference to
consider them distinct quantities.

Ethan
Received on Fri Sep 12 2008 - 15:13:01 BST