As part of its ongoing commitment to data quality, Ordnance Survey is undertaking a national Positional Accuracy Improvement programme. This programme will allow the capture of data at 1:2500 scale, to a greater absolute accuracy than previously (absolute accuracy is the position of features in relation to the Ordnance Survey National Grid). The PAI programme will result in an improved accuracy standard and more consistent mapping of data for rural areas. Furthermore, it will future proof the data for the addition of new building developments and other change, as well as providing a better relationship between Ordnance Survey 1:2500 scale map data and the mapping of customers' own GPS-positioned assets.

Due to the improved accuracy of the 1:2500 scale mapping, you will now see that features compared before, and after data has been through the PAI programme, may have been moved. If you have mapped your own company assets to fit in with the OS 1:2500 scale mapping, you are highly likely to find that they no longer fit with the new improved OS data. The OS provides a set of link files to it's customers that identify the amount of change from old to new position in any given area.

DOES IT AFFECT ME?  

If you use any of the Ordnance Survey rural maps of Great Britain, the answer is "YES".