in response to https://github.com/cf-convention/cf-conventions/pull/133#issuecomment-399911850
@davidhassell ``` If this proposal were to work, a grid mapping must be mandatory if the lats and lons were missing. ``` I would not object to an `either | or` condition here. ``` I have understood the purpose of providing the lats and lons to be that calculating them on the fly from the projection coordinates and grid mapping parameters was too much to expect of the dataset user (rather than the dataset creator). Perhaps this is no longer the case? If so, we should note this. ``` It is my assertion that this is not the case. I don't mind if this is deemed worthy of a note ``` I think that this issue is not independent from external_variables - allowing auxiliary coordinates to be external might, in some circumstances, allow the 2-d lats and lons to remain mandatory whilst addressing the file size issue. ``` I think that the issue of external variables for auxiliary coordinates is likely to take some time to resolve. If it were resolved to allow this, it would still put an onus on the data producer to provide all of these latitude longitude values somehow. The assertion here is that they are not required, they are fully calculable by a wide range of software, and so provision should not be mandated. That is the position I am adopting within the scope of this ticket -- You are receiving this because you commented. Reply to this email directly or view it on GitHub: https://github.com/cf-convention/cf-conventions/pull/133#issuecomment-409924422
