[CF-metadata] Standard name for land/sea mask

Lowry, Roy K. rkl at bodc.ac.uk
Tue Jul 11 08:42:28 MDT 2017

Dear Jim,

Just for information there are three other binary mask Standard Names (surface_snow_binary_mask, sunlit_binary_mask and cloud_binary_mask) providing a precedent for Elodie's proposal so as you say sea_binary_mask should be added to the collection.

Regarding your generic mask suggestion I'm not sure it gains us much as there can't be that many candidates out there for additional Standard Names. It also causes me some interoperability concerns - automated aggregation of files would complicated significantly by such generic labels.

For the more complex categorisation there is already a mechanism in CF, namely the area_type Standard Name and vocabulary. I'm not sure opening the gates to multiple variations on this themes would help users of the standard.

Cheers, Roy.

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From: CF-metadata <cf-metadata-bounces at cgd.ucar.edu> on behalf of Jim Biard <jbiard at cicsnc.org>
Sent: 11 July 2017 14:33
To: cf-metadata at cgd.ucar.edu
Subject: Re: [CF-metadata] Standard name for land/sea mask


Given the prior existence of land_binary_mask, Elodie's request for sea_binary_mask makes sense. Even given my request below, if Elodie needs this standard name, I endorse it's addition. I don't want to bog her down.

I'd like to suggest that we do something slightly more flexible and create the standard name discrete_mask, which could handle both these cases. It could also handle numerous other use cases that generally go without a standard name right now. The definition could be something like below.

discrete_mask: A variable with the standard name discrete_mask is used to indicate a finite set of discrete, related conditions that hold across the dimensional range of the variable. These conditions are marked by integer values, each of which indicates a specific condition. The particular conditions being indicated are defined using flag_values and flag_meanings attributes associated with the variable. A single element of the variable can indicate only one condition - bit field combinations are not allowed.

I'm thinking this way because in the particular domain Elodie is referring to, some files have trinary masks, sea = 0, coast = 1, land = 2, different ones define the numbers used to indicate the different conditions, some cover more cases (fresh water, for example), etc.

I do, on one level, appreciate that it can be nice to see the standard name on a variable and not need to look further to understand how the contents are implemented, but I don't think it buys us near as much as we like to think.

Grace and peace,


On 7/11/17 3:55 AM, Elodie Fernandez wrote:
Dear all,

I would like to suggest the addition of a new standard_name to describe land-sea masks. A standard_name already exists: land_binary_mask (
X_binary_mask has 1 where condition X is met, 0 elsewhere. 1 = land, 0 = sea.). But in the ocean modelling community, we have already existing files describing those masks, but from an "ocean point of view", so 1 is for sea and 0 is for land points.
So I would like to request the addition of the standard_name "sea_binary_mask",
with definition "X_binary_mask has 1 where condition X is met, 0 elsewhere. 1 = sea, 0 = land" and unit "1".

Best regards,

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