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Convert British National Grid to Irish Grid

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#1
Tim

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Hi all,

I'll introduce myself into the forums later but I've got a bit of an emergency and can't find anything useful on google.

I am plotting some points onto a map of Northern Ireland - I have the maps in Irish grid format, but the customer has supplied British National Grid points.

Does anyone know if there is a formula to convert the x and y from BNG to ING???

Thanks

#2
gregsd

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Hi all,

I'll introduce myself into the forums later but I've got a bit of an emergency and can't find anything useful on google.

I am plotting some points onto a map of Northern Ireland - I have the maps in Irish grid format, but the customer has supplied British National Grid points.

Does anyone know if there is a formula to convert the x and y from BNG to ING???

Thanks


Tim,

I thought BNG just covered the Great Britain (England, Scotland, Wales and outlying islands) and didn't include Northern Ireland? Until recently (2001) Northern Ireland was covered by the Irish Grid but has changed to the Irish Transverse Mercator (ITM) system, so the coordinates you've been provided could be in this?

Greg.


Greg Driver

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#3
Tim

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Hi Greg,

Thanks for your reply. I am not sure if the British National Grid was ever officially designed to cover Northern Ireland, but it can be extended to do so and in Easting terms never actually enters negative figures.

The co-ordinates provided by the client are derived from the Royal Mail PostZon data which I am pretty sure uses BNG for the entire dataset.

#4
gregsd

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Hi Greg,

Thanks for your reply. I am not sure if the British National Grid was ever officially designed to cover Northern Ireland, but it can be extended to do so and in Easting terms never actually enters negative figures.

The co-ordinates provided by the client are derived from the Royal Mail PostZon data which I am pretty sure uses BNG for the entire dataset.


Can you give an example of one of the postcodes and co-ordinates? I've not used PostZon data but we have access to CodePoint for the UK and I've just checked and NI postcodes are supplied in this dataset, which I hadn't realised! Anyway, the coordinates for the NI postcodes in CodePoint are Irish Grid (ITM). For example:
postcode - BT47 4SD -x= 276348, y=406390.

Greg.


Greg Driver

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