Thanks to all who replied to my original email, asking about the effects Positional Accuracy Improvement Program (shifts to map base) - On OS Landline / MasterMap datasets. I got some thoughtful and comprehensive replies. -My current understanding is summarised below.
Area Affected >- I understand PAI changes will only affect MasterMap at 1;2500 scale (ie. "rural" ) rather than 1;1250 - Have I got this right?> It seems that it is MAINLY the 1;2500 tiles that are affected - but some 1;1250 tiles that share a 1 km grid square with 1;2500 data will also be affected. There is a file at http://www.ordnancesurvey.co.uk/oswebsite/pai/programme.html that you can download listing precisely which tiles are affected. Timings >- Is there a list anywhere of when the changes will be applied to each tile? Or can you specify when you get new data whether you want pre or post PAI? There is a rolling program where transformations will be applied to areas gradually. Provisional Time Scales seem to be in place. http://www.ordnancesurvey.co.uk/oswebsite/pai/programme.html In a given area, you may at a particular time be at a transitional phase where adjacent tiles are not exactly matched - see http://www.ordnancesurvey.co.uk/oswebsite/pai/transforming.html It doesn't appear that you can specify pre or post PAI data - You get what your given Effect on Proprietary Data >- We have some proprietary data that is currently fitted to Landline Clearly this needs to shift when the underlying data shifts. What solutions are out there that will let us do this process in parallel with MasterMap? Software Solutions are listed at http://www.ordnancesurvey.co.uk/oswebsite/pai/softwareservices.html These over different ways (at a price) to shift your data in line with MasterMap, using Ordnance Survey free "link" files - Files listing the amount of shift across regions. The Ordnance Survey website offers fairly comprehensive coverage of how to handle the problem, but for most users it's going to be an administrative headache. I think there are 2 straightforward things the OS could do to make the transition process a whole lot easier for users - - Data Supply - Give people the option to order either Pre or Post PAI data during the transitional phase. This would let you make the transition for both OS data and proprietary data in a single changeover day, rather than painfully dragging the process out. - Software supply - Produce a freeware program that transforms standard GIS files (MIF/MID, SHP etc.) according to PAI. If the program applied the same mathematical transformation and link files etc. that the OS has applied to its own data, then exactly equvalent results would be obtained - maintaining "Node Accuracy", and removing the need to spend money on any of the software products listed. My personal opinions only. I'd be interested to hear what anyone else thinks. Cheers, Stephen * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * This email and any attachments with it are intended for the addressee only. It may be confidential and may be the subject of legal and/or professional privilege. If you have received this email in error please notify the sender or [EMAIL PROTECTED] The content may be personal or contain personal opinions and cannot be taken as an expression of the County Council's position. Surrey County Council reserves the right to monitor all incoming and outgoing mail. Whilst every care has been taken to check this outgoing e-mail for viruses, it is your responsibility to carry out any checks upon receipt. * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * --------------------------------------------------------------------- List hosting provided by Directions Magazine | www.directionsmag.com | To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] Message number: 9314
