Tag for Irish Grid Reference: advice

I am importing a NI archaeological dataset into OpenHistoricalmap (as it allows for the OGL licence and OSM does not) and a useful field is the Irish Grid Reference e.g. J4274078050. Can someone here advise the best key to use? I was thinking ref = * or maybe ref:igr = *

There is going to be over 16,000 elements when I get this done and a further 210,000 elements if I do the dataset from the whole of Ireland…in small subsets, and if I live that long! So whatever tag I use it will end up pretty high in the usage list.

I also have the townland name to import. I see townland names have been tagged under ‘hamlet’ which just doesn’t sit well. I am planning to use a new tag called ‘townland’. I know I don’t have to stick to the approved tags but I would like to if possible, however only if it accurately reflects what the element actually is.

I don’t have answers to your questions, I just wanted to mention that this forum doesn’t get a lot of attention, so you might also want to try the talk-ie mailing list:

There is no need to add Irish Grid to objects, it can be trivially calculated from the co-ordinates of an object on OSM or OHM (by a transform from WGS to Irish Grid). I would also check how accurate these co-ordinates are, the one you provide looks to be an 8 figure GR padded with trailing 0s, which may not be quite as accurate as you want (most of these objects should be visible on the GSGS 3906 layer which is probably accurate to 5m in most places).

Note that the reference you provide looks like an old Irish Grid, which has been superseded by the new all numeric 6-figure eastings & northings (I think called ITM). That being said I’m sure people on the ground will continue to use the familiar system.