A database solution for OS MasterMap in Medway

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A database solution forOS MasterMap in Medway
How to master OS MasterMap!!!

• Rachel Bull, GI analyst
• Gesche Schmid, ICT and information manager
• Medway Council

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Life before a database solution
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Application 1 Capturing highways assets

• Current situation
• Using inaccessible, outdated paper maps
• Requirement for first point of contact
• Make an updated highways assets map
  electronically available on GIS intranet and link
  it to highway asset management system via USRN
• Current Project
• Select likely highways assets by creating a
  MasterMap subset (Theme Roads, Tracks and Paths)
• Select polygons from the subset instead of
  digitising along lines
• Create new polygons or split OS MasterMap ones
  only where highways asset polygons differ from OS
  MasterMap

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Capture polygon and add USRN
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OS MasterMap benefits

• Reduced data capture cost and increased accuracy
  
• 3 times faster than digitising from Land-Line

Butlinking to TOIDs was not feasible because
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there isnt a 11 relationship between highways
assets and MasterMap polygons
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Application 2 Ranking of contaminated land

• Prioritise potentially contaminated sites where
  humans are the likely receptor
• Identify receptors (all houses with gardens)
• Select OS MasterMap buildings thematically
• Spatial query, select all buildings within
  contaminated areas
• Select OS MasterMap multi surfaces thematically
  (representing gardens)
• Spatial search buffer, find all multi surfaces
  which are directly adjacent to buildings

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Prioritised receptor area
Receptor Terraced houses and gardens
Source Historic land use
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OS MasterMap benefits

• Reduced data capture cost and increased accuracy
• Able to select all receptor polygons by thematic
  and spatial queries (no need to digitise the
  receptors)

But
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Medway were not managingOS MasterMap updates
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Problems with using file based data

• Change only updates cannot be managed and
  archived
• Only alternative is the continual creation of
  initial supply contracts with Ordnance Survey
• Data volume sizes are too large to process on a
  standard PC
• Complex spatial queries cannot be run for single,
  Medway-wide OS MasterMap layers (PC crashes)
• Processing data as a series of workable sized
  tiles requires significant additional
  administration

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Looking for a better solution
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Advantages of moving from flat files to a spatial
database

• Managing large, intact datasets
• Scalability (terabyte sized tables)
• Easy removal of chunk duplicate features
• Selective delivery of data to GIS
• More powerful spatial and non-spatial querying
• Managing change only updates
• Archiving and version control ensures data
  currency and facilitates generation of historic
  datasets
• Other benefits
• Interoperability with other systems through
  relational tables and cross referencing
• Controlled multi-user access

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Other drivers for a spatial database
GI Strategy and Infrastructure Review

• WAI (Web Accessibility Initiative) compliance
  requirement linkage of spatial database searches
  with the Councils GIS internet
• E-Government interoperability requirements
  integration of GI data with back-office systems
  and CRMS (Customer Relations Management System)
• GI data server replacement schedule

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Implementing the solution - Medways MasterMap
project
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System specification

• Server
• Dell Poweredge 2650 (Dual Intel Xeon Processor
  2.8Ghz , 4Gb DDR Memory, 5 36Gb Hard disks,
  Perc Raid Controller)
• Software
• Oracle 9i (Locator)
• Cadcorp SIS V6
• Cadcorp OS MasterMap loader

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Data requirements

• Holdings
• PAI and non-PAI
• Orders (Coverages)
• Three Ordnance Survey orders for PAI, Pre-PAI
  and Non-PAI areas
• Supply timetable
• Quarterly change only updates to coincide with
  Land-Line supply
• Additional change only updates for pre-PAI area
  as close to PAI implementation date as possible

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Data coverages
Initial Supply and PAI holding updates
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Data coverages
Non-PAI holding updates Pre-PAI area (06/03
08/04) real world COUs only
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Data coverages
Non-PAI holding updates Non-PAI area (08/04
Medway data PAId ) real world COUs only
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Design and implementation 1 Database

• User Control
• DB administrator (full control)
• GI administrator (updating data)
• GI user (read only)

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Design and implementation 2 Data loading

• Initial Supply (PAI schema)
• Original data 1.63Gb (gml)
• Load time 4.5 hours
• Storage size in Oracle (inc. index) 1Gb
• Change only update (2 months) (PAI schema)
• Load time less than 1 hour
• Final storage size in Oracle (inc. index) 1.24Gb

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Testing, feedback and modification

• Medway site testing was primarily done by GI team
• Resulting issues log was circulated and discussed
  between Cadcorp, GI team, Oracle DBA and networks
  to develop solutions

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Taking the solution to the user

• Awareness raising to warm users up
• Training super users to instil a new approach to
  GI data and gain feedback (file versus database)
• Preparation to facilitate wider mainstream use
  (simplify)

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Where Are We Now?

• Close to a workable application!

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What have we learned 1?

• 1. Assess the complexity and maturity of the
  system before you start
• Complex application
• Multi-skilled team - good communication is vital
• More complex fault finding
• Application in development / early adopter
• Dont under-estimate testing, feedback and
  modification required

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What have we learned 2?

• 2. Assess the data carefully
• New data format and supply
• 3. Keep focussed on the end user
• Users have difficulties with change and can offer
  invaluable feedback
• 4. Understand limitations to wide implementation
• Not everyone wants OS MasterMap
• External non-GIS specific software are not yet
  ready to link to database OS MasterMap

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Where Next..?

• Finish the job
• Implement all fixes
• Create best practice examples and applications
• Spread the use - train users
• Continue development
• Link to meta database tool (AGI Metagenie)
• Link to other applications
• Work with Ordnance Survey and software suppliers
  to improve the potential value of OS MasterMap

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• If only wed had the Wizard of OS when we started
  our quest to master OS MasterMap!

gesche.schmid_at_medway.gov.uk rachel.bull_at_medway.gov
.uk