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Re: EOL created netcdf files


Janet Scannell wrote:
> Hi John,
>
> Thank you for your response.  I have some more questions which I have
> included below.
>
> Thanks,
> Janet
>
> John Caron wrote:
>> Hi Janet:
>>
>> My apologies for taking so long to respond. The problem is that CF does not
cover point data adequately, and Ive been trying to formulate a proposal to CF
about this. Im afraid you will have to decide whether its worth waiting for
that to be an official standard or not. I can probably give you some reasonable
interim advice, but it may not end up to be standard.
>>
>> Looking at your files:
>>
>> 980101.PAM_Atl_met.nc looks fine as an unconnected collection of point data,
using existing CF Conventions. However, you may intend it to be a trajectory,
ie a connected collection?
>>
> Are there any restrictions on what should be considered a trajectory?
> According to the web site: "A  trajectory  is a collection of
> observations which are connected along a one dimensional track in space,
> with time increasing monotonically along the track".  The observations
> in the PAM data file are made from radio towers that are mounted on the
> sea ice.  The lat and long for the stations change continually because
> the ice is constantly shifting.  Therefore, it doesn't fit the rule that
> the observations are connected along a one dimensional track in space.
> Since the points are all from the same radio tower, I would think that
> they should be considered connected in some fashion.  Would a trajectory
> be the correct definition to connect all of these points together?

its an interesting "grey area" between a station time series, a trajectory, and
a point collection. technically, its closest to a trajectory, but it would be
up to you how to name it.

>
> I have also fixed the latitude and longitude so that there are not
> missing values for these variables.

good

>> BALTEX_Lindenberg_Falkenberg_20021001_20041231_sfc.nc is a time series of
station data, with only one station. Will all your files have only one station,
or do you want to be able to add multiple stations in the same file? If so,
will all stations have the same number of observations?
>>
>>
> We have decided that there will be only one station in each netcdf file
> for this dataset.

that makes things easy, and the need to clarify trajectory vs point collection
less important.


>> BALTEX_Lindenberg_Falkenberg_20021001_20041231_twr.nc has a couple of
problems:
>>
>> 1) rename variable "height" to "heights" so its a coordinate variable. (or
rename dimension "heights" to "height".
>>
>> 2) making the time variable two dimensional time(time, heights) looks like
its unneeded, ie it could be time(time)? If you really need 2D time, then you
must explicitly add to each data variable:
>>
>>   :coordinates = "time height"
>>
>> there are still some issues that i have to think about some more.
>>
>>
>>
>>
>>