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.
>>
>>
>>
>>
>>