Introduction to OS MasterMap

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Introduction to OS MasterMap
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What is OS MasterMap?

• OS MasterMap is a digital representation of the
  real world containing more than 450 million
  uniquely identified geographic features. It is
  updated daily as a consistent  framework for the
  referencing of geographic information in Great
  Britain.
• A framework rather than a single dataset
• Framework comprises various Layers Topographic,
  ITN, Imagery, Address
• Each Layer comprises a series of Themes
• www.ordnancesurvey.co.uk

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Land-Line versus MasterMap?

• Land-Line is a digital cartography producta map
  designed to be viewed on a computer
• OS MasterMap is not just about mapping
• OS MasterMap Topography Layer is a feature-based
  dataset many of the features correspond to
  real-world objects
• Each feature has a unique identifier called a
  TOID
• Allows you to build data associations and to more
  easily exchange information with other people or
  organisations
• As a feature changes to reflect changes to the
  real-world object it represents, its TOID may
  remain unchanged, according to welldefined
  feature lifecycle rules

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What scale is MasterMap Topography layer?

• For cartographic representation, OS MasterMap
  Topography Layer is captured and designed for
  display at 11250, 12500 and 110 000 scales in
  urban, rural and mountain/moorland areas
  respectively
• In GIS OS MasterMap can be zoomed over a wider
  range of scales
• The most scale-sensitive feature types, such as
  cartographic text and symbol features, are fixed
  in size and rapidly become less clear at smaller
  display scales
• OS MasterMap Topography Layer is also suitable
  for use in noncartographic applications where
  the concept of scale is less applicable

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What scale is MasterMap ITN layer?

• ITN is the definitive national road network for
  Great Britain
• provides a flexible foundation for publishing,
  transport, telematic and asset-management
  solutions
• can be fully integrated with all OS MasterMap
  layers
• not intended for cartographic purposes and
  therefore is effectively scale free

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Features of MasterMap 1

• Cleaner Data produced using data validation and
  topology structuring procedures that remove
  slivers, overshoots, undershoots and unnecessary
  vertices
• Polygonised Data - data has been polygonised
  where appropriate to form structured polygonal
  objects such as buildings, parks, roads and
  rivers
• Seamless datasets - the data is not limited by
  tile boundaries but forms a logically continuous
  database where features are not arbitrarily split
  at tile boundaries

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Features of MasterMap 2

• TOID - Topographic Object Identifier - a unique
  and persistent 16 digit number assigned to every
  object when it is created remains constant for
  the life-cycle of an object
• Change Only Update (COU) - COU is the ability to
  supply only those features that have changed
  since a specified date. Used to keep a data
  holding current without having to reload the
  whole dataset, or to identify changes over time
  in the data
• Additional attribution - objects have additional
  thematic and descriptive attribution
• Additional metadata - information about creation
  and modification dates and changes are included
  in the data

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Features of MasterMap 3

• GML (Geography Markup Language) - GML is an XML
  encoding for the transport and storage of
  geographic information. It is a standard data
  format defined by the Open Geospatial Consortium
  (OGC). OS MasterMap data will supplied in GML
  format
• Continuously maintained - the underlying source
  database is continually maintained by Ordnance
  Survey and is the most up-to-date and accurate
  product with national coverage
• Consistent framework - in the future other
  products (with different scales, content etc.)
  will be supplied within the MasterMap framework
• Multiple Layers - Topography and ITN (Integrated
  Transport Network) layers will be available

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Benefits 1

• Linking using TOIDS
• consistent framework used to link additional
  (locally held, user-owned) data
• sharing of derived data
• major benefit for teaching and research where
  specific objects can be identified and research
  data directly linked to the base map data for
  easy reference.
• Additional attribution
• includes information such as theme, descriptive
  group, descriptive term etc.
• increases the flexibility of data
• increases the potential uses of the data for both
  cartography and data analysis

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Benefits 2

• Cleaned data
• removal of small gaps, slivers, undershoots,
  unnecessary vertices etc
• data structured into polygons
• area features can be filled with appropriate
  representation
• added intelligence that can be used in further
  analysis such as what lies next to this
  building?
• Seamless dataset
• removes limitations of tiles
• data can be requested for any arbitrary
  rectangular area (possibly irregular areas at a
  later date)
• Specifying themes
• ability to request single themes rather than the
  whole dataset reduces data duplication and data
  storage requirements

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Benefits 3

• Change Only Update
• users can keep their data holdings up-to-date,
  while reducing the volume of data required to do
  this.
• allows maintenance of historical archives of
  local data holdings for temporal and historical
  studies
• GML
• a human readable, globally standard, vendor
  neutral transfer format
• can be transferred between systems without loss
  of information and can be used for both data
  download and supply via the internet
• Data format of the future for Great Britain
• Ordnance Survey intends to replace all current
  products with additional layers of OS MasterMap.
• A students knowledge of OS MasterMap will
  significantly enhance their future prospects