We have a number of operational products based on fixed lat/lon grids that we disseminate in near-real time. The ability to be able to send the lat/lon grid once and link to it as a coordinate variable from within the file would be very useful as it would save considerably on bandwidth costs while still keeping the products user-friendly. So this would be a welcome development for our purposes. Tim _________________________________________________________________________________________ Dr. Tim Patterson Instrument Data Simulation Expert Product Engineering/Test Data Coordination MTG Programme GEO Division EUMETSAT Eumetsat-Allee 1 64295 Darmstadt Germany Tel: +49 6151 807 487 Fax: +49 6151 807 7 E-mail: timothy.patterson@xxxxxxxxxxxx Web: www.eumetsat.int -----Original Message----- From: netcdfgroup-bounces@xxxxxxxxxxxxxxxx [mailto:netcdfgroup-bounces@xxxxxxxxxxxxxxxx] On Behalf Of Eugen Betke Sent: Wednesday, July 13, 2016 1:09 PM To: netcdfgroup@xxxxxxxxxxxxxxxx Subject: [netcdfgroup] NetCDF external links Dear NetCDF-Group, we have been working on NetCDF external link functionality. This allows NetCDF applications to create dimension variables which values are stored in an external file. Therefore, it uses the HDF5 virtual dataset (VDS) functionality. This is useful for, e.g., climate applications that rely on a variable per file and timestep configuration. The idea is to store the grid in a separate file and link our data to this grid. We already have our first working version. You find the patch and the examples on our page: http://wr.informatik.uni-hamburg.de/research/projects/bullio/netcdf_external_links/start Under the hood it uses HDF5 virtual datasets. VDS has the advantage of being compatible to the functions that are supported by oridinary datasets. Therefore, files containing VDS should be supported by the most software. There is a minor issue related to HDF5, the call H5F_try_close function fails, when ncdump trys to read data from an external dimension. So far we found a workaround, but we will fix this issue. It would be great if external link functionality could be supported by netCDF at some timepoint. We would like to improve our patch and for that reason we need your feedback. If you have some idea to the issue above, we would be grateful for each hint. Regards, Eugen _______________________________________________ NOTE: All exchanges posted to Unidata maintained email lists are recorded in the Unidata inquiry tracking system and made publicly available through the web. Users who post to any of the lists we maintain are reminded to remove any personal information that they do not want to be made public. netcdfgroup mailing list netcdfgroup@xxxxxxxxxxxxxxxx For list information or to unsubscribe, visit: http://www.unidata.ucar.edu/mailing_lists/ Any email message from EUMETSAT is sent in good faith but shall neither be binding nor construed as constituting a commitment by EUMETSAT, except where provided for in a written agreement or contract or if explicitly stated in the email. Please note that any views or opinions presented in this email are solely those of the sender and do not necessarily represent those of EUMETSAT. This message and any attachments are intended for the sole use of the addressee(s) and may contain confidential and privileged information. Any unauthorised use, disclosure, dissemination or distribution (in whole or in part) of its contents is not permitted. If you received this message in error, please notify the sender and delete it from your system.