Hi,

I notice this change introduced two power cables across the Firth of Forth. I can't find reference to these anywhere (and the voltage of 450kV doesn't tally any standard British power grid voltages). I don't suppose you remember where you got the data for these from?

The short answer is it's an educated guess. Once you have an eye for it, it's relatively easy to pick out from aerial imagery the main distribution lines which run between substations. In most of Britain (including all of Scotland), these are 33kV.

I've written some more detail on how to spot this stuff on the wiki: osm.wiki/WikiProject_Power_networks/Great_Britain

Happy to have this discussion and revert these changes if necessary. My take on it:
There's always some level of inaccuracy with undersea (and underground) objects. These are features which we'll never be able to directly survey, and I suspect we'll never be able to get hold of accurate maps for themajority as exact locations tend to be kept secret. Even the parts we do have maps for have accuracy in the kilometers at best. So where do we draw the line?
In my view, the main interest with submarine cables is where they land at each end - this is something we can survey and determine from open sources. For that reason, I think the speculative routes make more sense than cables which suddenly end mid-ocean.

Currently these objects are not rendered on the main map, and I think it's unlikely they will be. So I'd argue that it's better for these features to be less accurate but more complete.