Ordnance Survey – Great Britain's national mapping agency
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The questions below are specifically for OS MasterMap Topography Layer. Please click on the frequently asked question to view the answer.
If you wish to search all the OS MasterMap FAQs please use the search box on the right, or return to the generic OS MasterMap FAQs page.
How often is OS MasterMap Topography Layer updated?
What is the difference between Topography Layer and Land-Line®?
How can I find out if a certain type of real-world object is included?
How do I find out which theme a certain type of feature will be in?
In OS MasterMap Topography Layer, what are inferred links?
Why are there inferred line features when they do not exist in the real world?
What scale is OS MasterMap Topography Layer data?
How are the Topography Layer and ITN Layer roads themes different?
How do I order OS MasterMap Topography Layer?
How is PAI delivered in OS MasterMap Topography Layer?
When is PAI data released in OS MasterMap Topography Layer?
Can we select COU by OS MasterMap Topography Layer theme?
Are there political boundaries in OS MasterMap Topography Layer?
How accurate are the political boundaries in the Topography Layer?
In OS MasterMap Topography Layer, what is a topological complex?
Do Topography Layer boundaries represent legal property extents?
How are collar tiles depicted in OS MasterMap Topography Layer?
How do I determine the captured accuracy of a feature (capture scale)?
What do 'absolute positional accuracy' and 'relative positional accuracy' mean?
How many polygons in the Topography Layer are incorrectly classified?
What features are held as topographic lines but are not in as topographic areas?
Do all the Topography Layer polygons have land use classifications?
Where are the building seed points in OS MasterMap Topography Layer?
Why can multiple classifications exist within the same polygon?
How do I remove duplicate features in OS MasterMap Topography Layer?
Why do I have duplicate text and how do I remove it?
What geometry tolerances are used in OS MasterMap Topography layer data, and how are these applied?
A feature has moved, but the reasonForChange says "Attributes". Why is this?
How do you deal with a feature that changes for more than one reason?