in response to 
https://github.com/cf-convention/cf-conventions/pull/133#issuecomment-408439318

@erget I don't think that this is sufficient.  The satellite case with FOVs and 
FORs only represents a subset of the problem cases here.

By mandating the provision of latitude and longitude coordinates and providing 
the grid mapping definition capability, CF is forcing data producers to define 
detailed information about position twice in many cases.

For example, a simple model grid using the UK's OSGB Transverse Mercator CRS is 
fully defined by the OSGB parameters, a 1D array of eastings and a 1D array of 
northings.  
However, to meet the CF conformance requirements, then a 2D array of latitudes 
and a 2D array of longitudes must be provided.  If only 1 data variable is 
provided at the surface, a common use case, then this ~triples the size of the 
file.
Pretty much any spatially aware application would be able to use the OSGB 
coordinates and CRS definition to geo-locate this data set, so the latitude and 
longitude arrays are really not required.

I think it is a better approach to remove the mandate that latitude and 
longitude values will always exist within the file.

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