Proposal: New area file format

[pytroll]

Proposal: New area file format

[pnuu]

My first very-very-late-night-two-pennies:

• resample each channel to target definition using original resolution, avoid reducing data prematurely, and then you'll get the maximum coverage without losing any details from the higher resolution channels
• projection units depend on the projection, e.g. quite many of EPSG projections have both metric and degree based versions

[djhoese]

Point 1: Agreed. Although for testing or for the rare case that you want an image in the original sensor space the replication or reducing of data to fit the other datasets.
Point 2: I'm not sure I understand what you're saying. Yes the projection units depend on the projection but why does that matter? Each Area listed in the config will have a projection specified and that's how extents work currently.

[djhoese]

If we put the actual file format to the side for a moment, what if AreaDefinition had something like this for its __init__:

    def __init__(self, area_id=None, name=None, proj_id=None, proj_dict=None, x_size=None, y_size=None,
            area_extent=None, nprocs=1, lons=None, lats=None, dtype=np.float64,
            center=None, pixel_size=None, ...<other defining properties>...):

Knowing @mraspaud the way that I do and the arguments we've had on other projects I'm sure he'll hate how many arguments there are, but that's kind of the point. The above would be backwards compatible for anyone not using named arguments but would allow users to specify whatever they know and get a working AreaDefinition out of it.

Another option I can see working is to have class methods that create the AreaDefinition based on what "scheme" the user is using. Problem with that is a user might not know what scheme they are using, some of the parameters overlap between schemes, and whatever loads the config file would need to figure out which class method to call.

[mraspaud]

@davidh-ssec YAML support was added a while ago, can we close this ?

[djhoese]

No, I'd like to keep this open until we have all the available forms of creating an area. It is something I'd like to do soon for geo2grid but Kathy has asked for other things first.