I have a question regarding coordinate variables:
I am working with time-series data representing hydrological conditions at fixed locations in a stream network. The values are generated by a model at regular time intervals, and I believe that the data will fit well into the timeSeries feature type described in the ?Discrete Sampling Geometries? chapter of the CF conventions. For example, we would put all the discharge values into a single 2D array:
double flow(time, location)
The dimension ?location? here is the ?instance dimension? described in the convention.
I would like to use an integer variable named ?location? as a coordinate variable to go along with the location dimension. I think this would provide a handy way for post-processing programs to locate a time series in our model result files. The Best Practices guidance on the Unidata website, though, says that coordinate variables ?must be strictly monotonic? and the order of the IDs in my location variable is arbitrary. All of the location values are unique, but the location numbers are essentially numerical labels ? location 1524 is distinct from location 2817, but neither is greater than the other in a way that means anything to the model. Location IDs do not consistently increase or decrease traveling downstream, for example.
So, is the guidance that coordinate variable should strictly increase or decrease relevant to my case? I?ve built some sample files and examined them using Panoply, and in Python using xarray. I haven?t seen any problems with using non-monotonic integer ?ID numbers? as coordinate variables, but that ?must? in the guidance troubles me. If my locations are identified by arbitrary numbers, do I run the risk of scrambling the links between my time series and their identifiers?
Thanks
Tom Evans
[cid:image9ef98c.PNG at 58bab801.4bad83a3]<
http://www.niwa.co.nz>
Dr Tom Evans
Software Developer
T +64-7-859-1832
National Institute of Water & Atmospheric Research Ltd (NIWA)
Gate 10 Silverdale Road, Hillcrest, Hamilton
Connect with NIWA: niwa.co.nz<
https://www.niwa.co.nz> Facebook<
https://www.facebook.com/nzniwa> Twitter<
https://twitter.com/niwa_nz> LinkedIn<
https://www.linkedin.com/company/niwa> Instagram<
https://www.instagram.com/niwa_science>
To ensure compliance with legal requirements and to maintain cyber security standards, NIWA's IT systems are subject to ongoing monitoring, activity logging and auditing. This monitoring and auditing service may be provided by third parties. Such third parties can access information transmitted to, processed by and stored on NIWA's IT systems.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <
http://mailman.cgd.ucar.edu/pipermail/cf-metadata/attachments/20190708/146efd10/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image9ef98c.PNG
Type: image/png
Size: 12288 bytes
Desc: image9ef98c.PNG
URL: <
http://mailman.cgd.ucar.edu/pipermail/cf-metadata/attachments/20190708/146efd10/attachment-0001.png>
Received on Sun Jul 07 2019 - 19:51:19 BST
