National Grid / ITM - Surveying

For precise mapping over large distances a National Grid system is used. PCA can provide survey data referenced to the National Grid in either IG (Irish Grid or IG75) or ITM (Irish Transverse Mercator) formats.These two National grid systems still exist in tandem in Ireland. The ITM(officially released by OSI in 2002) is the more modern of the two systems and is more reliable.It is highly recommended over the older IG75 for engineering design as there is less distortion due to scale factor.

Most Surveyors,Engineering consultancies, the OSI and the PRA are now using the ITM version of National Grid.

The older IG 75 is still in use by many local authorities.

PCA can produce surveys in either format or in certain cases such as the Dublin Port Tunnel, PCA issued survey data in both formats by request.

For more information on the National Grid see "Best Practice Guidelines on Precise Surveying in Ireland" on the IIS website.