Alignment of BAG, BlueTopo, and S-102 metadata layer fields

[brian-r-calder]

Background

After the BAG format developed (starting 2003, and announced at the Shallow Survey conference in 2005), it was adopted as the core ideas behind S-102; BlueTopo is an implementation of gridded layers of bathymetric information made available through NOAA's compilation of "best available" data throughout the US region of responsibility.

In all three systems, there is provision for a metadata layer that allows for specification of the metadata associated with different data sources compiled into one file; this was based on a specification proposed by NOAA/OCS, which is profile 2022.10 for BAG 2.0.1.

There is potential for these implementations to diverge, which would be a very bad thing. We need to consider the requirements for these layers, and any modifications that we would like to see happen before S-102 becomes v 3.0.0.

Actions

1. Describe the current situation with the NOAA profile of the metadata layer, and concerns about compatibility.
2. Discuss any suggestions for modification required, particularly with respect to S-102 (which may take longer to happen).

[johnsonst]

I think we should be able to get required metadata close between the various projects, but there will likely always be optional fields that will differ between them. Therefore we can strive for a goal for them to be the same but will have to accept that we might have to settle for being close different entities control the standards, even if several of us are involved with all three.

[giumas]

It is true that S-102 was initially inspired by BAG, but the two product specifications diverged years ago.
BAG format is mainly used for data exchange, while S-102 products aim to be used on an ECDIS for navigation (and follow the S-100 data model).
As such, is it worth to put efforts in aligning the BAG and S-102 metadata? Also because it would likely mean at this late stage of S-102 PS that BAG metadata have to align to S-102 (and not the opposite).

[GlenRice-NOAA]

While the format specifications have diverged I am not sure the information carried by each is significantly different. In both cases, the goal is to carry bathymetry and other navigationally relevant information. If there is a difference I think it is worth asking why. In general, I think there should be minimal translation of the information carried by each to reduce information loss or obfuscation.

The context for this particular issue is to align the metadata profile with S-102, and make sure we are asking if each has what it needs. I agree that the process for updating S-102 may be more cumbersome, but that doesn't mean the larger navigation community shouldn't review each specification and make sure it suits the need. I think it should be easy to add another metadata profile to BAG as we have configured it.

The one field in S-102 that concerns me is bathyCoverage. The definition seems reversed to me.

I have attached a crosswalk in case it is helpful: BAG_S-102_BlueTopo_Crosswalk.pdf

[GlenRice-NOAA]

For a more current link to the in-development S-102 Product Specification see here.

[brian-r-calder]

See comments in meeting notes from the WG discussion at CHC'24 here; this is slated for future discussion at the next WG meeting.