Alderney trig points incorrect location

[stripytrigger]

Not sure who can fix this, but I noticed that the location of the following four trigs is totally wrong. I don't mean a minor error, they're showing as way out in the Atlantic, nowhere near Alderney.

TP25773 "Le Rond But (Alderney)"
TP25774 "Telegraph Bay (Alderney)"
TP25776 "Giffoine (Alderney)"
TP25777 "Essex Hill (Alderney)"

All four have some coordinates supplied in the logged visits, so those seem like reasonable coordinates to use if there isn't anything more official.

[agentmancuso]

We can't fix this, despite having good coordinates, because Alderney lies outside the OSGB grid; hence the map defaults to the origin point of that grid.

[stripytrigger]

Thanks agentmancuso, that's interesting.

Let's ignore the visual map for a moment - I still think the displayed grid reference is wrong. E.g. for https://trigpointing.uk/trig/25773 the grid reference is shown as WA 57817 06737. From eyeballing the diagram on the top left of https://upload.wikimedia.org/wikipedia/ ... l_Grid.svg it would appear that anything in the channel islands should have a grid reference beginning with X, not W.

Unless you're saying that T:UK simply doesn't support storing those grid references? If this is the case I wouldn't expect it to be happy with a reference starting with W either, which it does appear to display happily enough. Additionally, the four entries mentioned in my previous message all have different grid references, suggesting they represent specific locations, rather than simply defaulting to some origin point (as you'd expect them to all the be same in that case).

I am aware that there are accuracy issues outside of the main OSGB grid, and that many algorithms simply won't convert grid references outside of this grid. However, I assume that T:UK stores/displays locations as grid references and thus there are no other options to store the coordinates (without someone doing a lot of work to change how T:UK works) - but I think that having an accurate-ish grid reference is still worthwhile if possible.

[agentmancuso]

The GR10s displayed on individual pages are (at least reasonably) accurate. But they are displayed in a format that commonly appears on local mapping in the Channel Islands, (a version of UTM I believe) not in BNG, precisely because they stand outside that grid i.e. south of the 'X_' square.

[stripytrigger]

Oh, that makes much more sense! For some reason I didn't even think that they might be anything other than BNG refs. Thanks for clarifying