||The original sources for the information displayed in this dataset were the exhibition maps for each Arterial Drainage Scheme constructed under the Arterial Drainage Acts 1945 and 1995. These maps were digitised between 2001-2004 from Ordnance Survey of Ireland 1:10,560 six-inch raster data in Irish Grid. Distortion arises from the historic Cassini map projection used in the original maps. Scale along the central meridian and at right angles to it is accurate, but everywhere else, scale, and therefore mapped objects, are distorted in a north-to-south direction. The amount of distortion on the map increases with distance from the central meridian. In Ireland, the Cassini projection was applied on a county-by-county basis for six-inch mapping, with the central meridian passing through a point near the centre of the county. Therefore, distortion is most evident near county borders, and also in rivers, lakes and streams. Distortion and error inherent in the dataset are amplified during translation and re-projection using Irish Grid and Irish Transverse Mercator. In general, as channel maintenance work proceeds, some errors may be found and these are corrected on an ongoing basis. In 2019 an exercise was carried out to correct directional issues within the dataset to allow for correct automatic chainage generation.