PAI Toolbox

The undertaking of the following steps is suggested to gain a first, high-level understanding of the effect PAI will have on your datasets: 

• Read the high-level PAI introduction written by Robin Waters, RSW geomatics and AGI Council member. This document could also be passed to senior management to give an overview of PAI and possible implications.
• Consult the release schedule to find out when data in your area is going to be released. Since the programme may change it is recommended to revisit this site on a monthly basis.
• Understand the main mechanics of the programme, particularly the differences between the rural sweep and the rural town programme.
• If you use OS MasterMap^® understand the differences of the release mechanism in OS MasterMap.
• If you use OS MasterMap or your strategic plan incorporates the take-up of OS MasterMap before the end of the PAI programme (before March 2006), order pre–PAI data in OS MasterMap the month before it is released for a particular area. This will allow you greater flexibility in the decision about the shifting methodology later in the process, to enable you to use methods that access pre–PAI OS MasterMap data.
• Make a decision whether you want to upload post–PAI data into your live system. Most of the current experience indicates that it is preferable not to do this until the implications are fully understood (steps that will lead to a deeper understanding are outlined in the revised risk assessment phase). 
  There are generally three different options: 
  (i) load data to access most current map; 
  (ii) don't load the post-PAI data and freeze the existing base map; and
  (iii) work with two different ones, a frozen base map and one where PAI updates are loaded into.

Be aware that all subsequent deliveries of Land–Line^® or OS MasterMap will contain post–PAI data in the areas where PAI has been released. If you decide not to load the data, PAI areas should be filtered out of subsequent updates.

The first risk assessment should examine the effect the change of the base datasets (Land–Line or OS MasterMap) has on the datasets that are obviously the most crucial for the organisation. For a local authority these usually include BLPUs, planning applications, land charges and land terrier. 

Ordnance Survey has analysed typical PAI shifts and found that the majority of the link vectors are less than 2.5 m. Exceptional shifts of greater than 8 m  have been experienced in a very limited number in isolated areas. Link file statistics for released blocks can be viewed here.

Why PAI is important - statements

Many Local Authorities have made a significant investment in Geographic Information.  Much of this information has been captured against Ordnance Survey base mapping and is intended to 'fit' the map.  The advent of sophisticated low-cost satellite GPS surveying equipment has highlighted anomalies in existing maps and demanded that rural areas in particular are re-surveyed to a higher quality.  The effect of the improvements to the base maps is that information captured before improvements may no longer 'fit' the base map.  Understanding the impact of PAI is essential to improve the quality of captured information and ensure sympathy with base mapping.  Properly corrected data is easier to maintain, unambiguous to share, and able to support automated constraint checking applications such as planning or land searches.

David Renn, Stockton-on-Tees Borough Council

"The successful completion of PAI is vital to any organisation's data management, which, within local government, is the fundamental component to ensuring the successful completion of e-government initiatives such as NLIS and NLPG."
Peter Roper, East Staffordshire Borough Council

"The inaccuracies of datasets as a result of PAI are up to 6 m within Medway which is legally not acceptable in the landcharges and planning approval process and may have catastrophic effects in the case of emergencies. The risk to the Council  for failing to adjust the planning and other constraint map layers to PAI may cause decisions to be made on the basis of incorrect, out of date information, which may result in legal prosecution. The risk is 66%."
Gesche Schmid, Medway Council

"PAI WILL have an impact on your business. You will have to plan what  data you will need to move, how to move YOUR data and carry out a QA to make sure your data has been moved correctly. The future of YOUR information holdings are at risk if these procedures are not carried out."
Frank Hodges, Stratford on Avon District Council

"As a Council who were hit by the very first PAI release we are fully aware of the problems. "The Earth moved for us" in a very big way with some movement in excess of 4 m. You will need to audit your data holdings, plan what you need to move including deciding which databases are business critical, move your data - software is now becoming available to assist  - and carry out a QA on that moved data.  We can assure you that most Local Authorities will be affected by Positional Accuracy Improvement which will
also contain "real world" change. It is critical that your data is transferred to its new position correctly. In many instances your ability to meet the Government targets for electronic delivery of services will depend on accurate geographic information."
Frank Hodges, Stratford on Avon District Council

"Good quality, accurate information is essential to many of the services carried out by local authorities. These services range from statutory functions such as the recording of planning applications and the preparation of development plans, through to operational activities such as measuring site areas for land disposals and home to school distances for the provision of school transport.
As mapping technology changes the quality and accuracy of maps can be improved. While improvements are to be welcomed, it is important for mapping users to recognise that improvements may impact on data already held against a map base and indeed information derived from it. In some cases it may be necessary for the mapping user to rematch their captured data to the improved map base.
The decision to rematch data will be based on a number of factors, including the quality and accuracy of the mapped data, the need to improve the quality of the original data and any potential legal implication of rematching the data or leaving it as is. These are important issues and there is no single answer which is correct in all situations. It is, therefore, of vital importance that an assessment on the implications of any course of action is carried out. To do so will require a full understanding of data and its use. This assessment should be complete before a commitment to a course of action is taken."
Craig McCorriston, West Lothian Council and chairman of the LoGGIC PAI Sub–Group

Back to Am I affected      Forward to Find a sponsor