Dataset Overlaps.

[kusala9]

C-21.2 needs updating. NIPWG10 agreed that certain S-12X products would be expected to overlap ENCs of other data producers, i.e. that the data producer of the ENC and the overlapping S-12X product would not be the same. NIPWG10 agreed a clause explicitly stating this could be added to S-98.

Separately, discussions on WLA implementation have highlighted the problems that would be caused by overlapping S-102 and S-104 coverage (i.e. where multiple S-102 datasets or multiple S-104 datasets overlap each other). This should be explicitly disallowed in S-98 Annex C (and, separately raised as compatibility issue in the validation tests). This issue only tracks the updates to S-98 Annex C in respect of these changes.

[rmalyankar]

S-123 is another product where data coverages in adjacent datasets might overlap including datasets from different producers, for example radio coverage areas of stations in neighboring countries.

[bhell]

For WLA the situation might be more complicated, because "official" oceanographic data (S-104) could be produced by e.g. a national metocean office, which is not the corresponding hydrographic office that produces the relevant S-102 cells. Leading to the situation where the HO in some way would need to certify that S-104 from another producer code is ok to use for WLA.

In the Baltic Sea (and probably also other places in the world) it is quite likely that we even agree regionally (e.g. within the regional hydrographic commission) on one single metocean office to produce "official" S-104 models for the entire region, spanning across various HO's areas of responsibility. At the same time, a higher resolution S-104 model could be made available nationally/locally for e.g. to be used by pilots in a specific port. Both models would overlap and be officially valid in the same location, but probably not in within the same "scale band" or navigational purpose.

Just forbidding overlapping WLA datasets or restricting WLA to function for a data stack from one single producer code might be too restricting.

Based on an IIC paper (and another related one), such points were already touched upon at TSM9, partly referring the issue to WENDWG.

[kusala9]

i agree with all the points raised in the previous comment. In fact it was these kinds of issues that led me to raise the paper in the first place but it was not accepted by TSM, and referred to WENDWG for a "soft" solution - i.e. one where there is no defined technical means to resolve overlaps or match chart data to non-chart data which overlaps it. These were also issues raised in the Governance document but currently S100WG (and S-98) has no position on these. So, I believe the current trajectory of S-98 is to

• note that overlaps are likely to exist between NavPub products and ENCs from different producers (this was asked for specifically by IEC at the NIPWG meeting
• Note the link between overlaps of other products (S-102/S-104) and the correct functioning of WLA, that is, WLA is designed to only be implemented with single datasets of S-102 and S-104, not any combination formed by an overlap. The ECDIS will be forced to choose in the event of an overlap and inform the user.

If a stronger technical means is desired, then it needs to be proposed through the S-98 subgroup and included in the forthcoming edition - there's nothing to stop this but we would have to propose it and get it through TSM in March as a resubmission.