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Definitions and Information

What is a Trig Point?

How is a Trig Pillar Made?

What is Trigpointing?

What is a Bench Mark?

About Trigpointing Ireland

About Trigpointing Ireland

In the summer of 2006 I started walking in the hills around Belfast to get some exercise. I soon discovered that some of the summits had concrete structures on them and upon investigation, learned that they were Triangulation Pillars. I started logging my visits to these sites on a website, but quickly discovered that it was based on the British Grid and did not fully support Ireland.

Trigpointing Ireland was created in November 2006 to fill that gap. I had no idea if anybody else in Ireland was interested but I was content to use the site as a sort on online diary for myself. Originally I was only interested in TPs on hills but decided that I would visit as many as possible, just for the sake of completeness. I added a facility to allow others to register so that they could upload condition reports and photographs.

The database and maps were all updated manually on my PC. I then had to created up to date lists and map images and upload them to the site. As more people got involved, it became increasingly difficult for me to do this so I upgraded the server to include online database faclilites and proceeded to learn how to use them. Many of the pages now contain dynamic data. For example, the statistics, Map and recent reports list on the fron page all update automatically as more people register, as new reports are received and as new records are added to the database.

The growing membership has wider interests than I, and requests were made to include OS marks other than TPs. In February 2008, this support was added to the site.

OS Marks Currently Supported

Abbreviation Type
PTPPrimary Triangulation Pillar
TPTriangulation Pillar
NPFBNon PillarFlush Bracket
BMBench Mark other than a FB
PGPSPassive GPS Station
BTBase Tower

We are still a relatively small band, but I am encouraged enough to continue developing the site. Why not register so that you can contribute to our knowledge base and have a say in what the site provides.

James Carroll

Ordnance Survey
in Ireland

1824 Ordnance Survey Ireland (OSi) established. Major survey by Thomas F. Colby begun.
The History of Ordnance Survey

The Lough Foyle Base Line
The first levelling of Ireland.
Poolbeg Datum
1846Colby's survey was completed.
1867A more comprehensive survey was completed.
1921Ordnance Survey N.I. set up
1952Northern Ireland Retriangulation
1957A new vertical datum for NI.
Belfast Datum
A combined datum for OSi and OSNI was also established at Malin Head.
1959Republic of Ireland Retriangulation
1970The work of adjusting the observations from the Republic of Ireland and from Northern Ireland to form one entire network related to MSL Mailn was completed.
Malin Head Datum