Ordnance Survey Ireland


Ordnance Survey Ireland has evolved from the Ordnance Survey Office which was established in 1824.  This office was initially part of the army under the Department of Defence.  All staff employed by the Office were military until the 1970s when the first civilian employees were recruited.

The Ordnance Survey Office was created to carry out a survey of the entire island of Ireland to update land valuations for land taxation purposes.  The original survey at a scale of 6 inches to 1 mile was completed in 1846 under the direction of Major General Colby.  Ireland thus became the first country in the world to be entirely mapped at such a detailed scale.  It was a remarkable feat by remarkable men and the accuracy they attained is still marvelled at today.  The process involved both innovation and ingenuity.  For example, to establish an accurate "baseline" for the entire survey, Colby developed a measuring system which incorporated two parallel bars of different types of metals.  Once the baseline was established, the surveyors used triangulation between mountain tops to create a framework of reference points for the entire country.  Some of the sides of the primary triangles were over 150 kilometres in length.  To spot points accurately at such great distances Lt. Col. Thomas Drummond devised the intensely bright limelight - which later became popular as a means of stage lightings.

In the course of surveying the country, the staff of the Office was responsible for a number of advances in surveying practice ranging from Drummond's limelight to the bimetallic parallel bars used to measure distance to a previously unattainable level of accuracy.  The drive to improve technical capability has continued to remain a prime value in ordnance survey work to the present day.

The Office was located in Mountjoy House in the Phoenix Park.  Mountjoy House was originally built in 1728.  It later housed the mounted escort of the Lord Lieutenant who resided in the Vice-Regal Lodge (now Áras an Uachtaráin).  Mountjoy House and its surrounding buildings still serve as headquarters.

The Office continued to operate under the agency of the Department of Defence for 80 years until 1924 when central responsibility for it was transferred to the Department of Finance.  

Ordnance Survey Ireland operated as part of the civil service area of Government until 2002 when it became a semi-state body under the Ordnance Survey Act 2001.  Under this Act, Ordnance Survey Ireland continued its mainstream public service function of creating and maintaining the definitive mapping records of the State and also assumed the commercial function assigned to it under the Act of developing its commercial business and sales revenues.

Central responsibility for Ordnance Survey Ireland was transferred from the Department of Finance to the Department of Communications, Energy and Natural Resources on 1st January 2008.

For more information, log onto www.osi.ie

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