1. Ⓒ AYLESBURY VALE DISTRICT COUNCIL Moving with OS MasterMap A proposed methodology for using MasterMap to manage changes Martyn Sutcliffe OS PAI/Change Management Seminar 2003

2. Ⓒ AYLESBURY VALE DISTRICT COUNCIL The Problem: A changing background Past Changes Real World Positional Accuracy Improvements Manual checking and update Duplication of Realignment

3. Ⓒ AYLESBURY VALE DISTRICT COUNCIL The Solution: Manage the Change Where possible automate realignment Cascade changes to other features and datasets Identify features that need updating

4. Ⓒ AYLESBURY VALE DISTRICT COUNCIL Aims of Methodology Ensure spatial data is maintained fit for purpose Decrease the current time delay in realigning features Decrease the amount of resource required to maintain relative accuracy

5. Ⓒ AYLESBURY VALE DISTRICT COUNCIL The Method Build a relationship between features and MasterMap polygons Use the changes in MasterMap polygons to identify the features to change Use the MasterMap changes to model the required change in feature geometry

6. Ⓒ AYLESBURY VALE DISTRICT COUNCIL Building the Relationship Identify the related MasterMap polygons Determine the type of relationship Full Match Part Match Align the shapes Record the relationship Full Match Part Match Feaure_IdTOIDVersionMatch_Type 19332331000436875435632Part 19332331000090234324234Full

7. Ⓒ AYLESBURY VALE DISTRICT COUNCIL Identifying the features to change Find the changed MasterMap polygons Use the cross reference to find the features to change Check for real world changes

8. Ⓒ AYLESBURY VALE DISTRICT COUNCIL PAI: Creating the candidate geometry (aligned edges) Find previously aligned edges Find the edges on the new MasterMap polygons Form any simple closures Measure the changes

9. Ⓒ AYLESBURY VALE DISTRICT COUNCIL PAI: Creating the candidate geometry (closures) Aligned vertex – use realigned vertex Vertex on edge – use measure to create new vertex Free vertex – transformed using links related to the MasterMap polygon A1A1 A2A2 B1B1 B2B2 C1C1 C2C2

10. Ⓒ AYLESBURY VALE DISTRICT COUNCIL Validating Links and Identifying Real World Change Test link pairs Real world change between links Length Angle

11. Ⓒ AYLESBURY VALE DISTRICT COUNCIL Accepting the changes Each candidate feature is measured to determine the shape change Where changes are within the tolerance the candidate shape is accepted automatically Where changes are larger, tools allow human validation and editing of the candidate geometry Where candidate not formed, tools assist user to create the new shape

12. Ⓒ AYLESBURY VALE DISTRICT COUNCIL Cascading The Changes Identify and Record Matching Shapes Validate Updates Automate Updates

13. Ⓒ AYLESBURY VALE DISTRICT COUNCIL Working Together There may be a case for working with different organisations to Manage Changes Potential reduction in duplication of data Potential for managing PAI and change management across different organisations Potential to cascade changes across authorities Potential to share experience and resources

14. Ⓒ AYLESBURY VALE DISTRICT COUNCIL Contact details Martyn Sutcliffe Aylesbury Vale District Council Email: msutcliffe@aylesburyvaledc.gov.ukmsutcliffe@aylesburyvaledc.gov.uk