Compare OS MasterMap and OS OpenData: A Side by Side Comparison for Professionals

Coverage, Detail and Update Frequency Compared

Ordnance Survey provides a wide range of mapping datasets, from free public data to highly detailed commercial products. Two of the most commonly discussed datasets are OS MasterMap and OS OpenData, so let's compare OS MasterMap and OS OpenData.

While both datasets originate from Ordnance Survey, they serve very different purposes.

OS OpenData is a collection of free datasets released by the UK government to support innovation and transparency. These datasets include products such as:

• OS OpenMap Local

• OS Boundary Line

• OS Terrain 50

  
  

These datasets provide general geographic information that can be used for mapping, research and basic spatial analysis.

OS MasterMap, on the other hand, is a premium dataset designed for professional use. It offers a far higher level of detail and accuracy than the open datasets.

For example OS OpenMap Local may represent a building as a simple block shape. MasterMap provides precise building outlines along with boundaries, walls, land parcels and surface features.

When Free OpenData Is Enough

In some situations OS OpenData may be perfectly adequate. If you are creating a general map for a report, visualising data at a regional scale or building a public information website, the free datasets can be very useful.

They are also commonly used in academic research and educational projects. As the data is free and openly licensed, it can be distributed widely without the licensing restrictions that apply to commercial mapping.

When You Need OS MasterMap

For professional design and planning work, OpenData is usually not detailed enough. Planning drawings, infrastructure design and engineering analysis require precise mapping that accurately represents buildings, boundaries and transport networks. This is where OS MasterMap becomes essential.

MasterMap offers:

• Higher positional accuracy

• Significantly more mapped features

• Object level identifiers for each feature

• Regular updates to reflect changes on the ground

For architects and planners submitting drawings to local authorities, licensed OS mapping is often required to ensure plans meet planning validation standards.

Data Structure and File Formats

Another major difference between the two datasets is how they are structured. OS OpenData products are typically simplified datasets designed for easy use in mapping applications. OS MasterMap is structured as a detailed geographic database. Features are stored as objects with associated attributes and identifiers.

This allows professionals to integrate the data into GIS, CAD and BIM workflows.

MasterMap can be supplied in formats such as:

• GML

• GeoPackage

• DXF

• DWG

These formats allow the data to be used directly in software such as AutoCAD, ArcGIS and QGIS.

Compare OS MasterMap and OS OpenData

When deciding which dataset to use it helps to consider the purpose of the project. If you need general geographic context or are working on a public information project, OS OpenData may be sufficient. If you are preparing planning drawings, analysing a development site or designing infrastructure, OS MasterMap will almost certainly be required.

Accessing OS Mapping Data

Both datasets are available through different channels. OS OpenData can be downloaded directly from the Ordnance Survey website, or we offer an affordable instant download in pdf format. OS MasterMap is available through licensed partners, such as ourselves which allow users to extract data for specific areas of interest.

This approach makes it easier for professionals to obtain the exact data they need without downloading large national datasets.

Conclusion

OS OpenData and OS MasterMap both play important roles within the UK mapping ecosystem. OpenData provides accessible geographic information for general use while MasterMap delivers the high precision mapping required for professional planning, engineering and development projects.

Understanding the differences between these datasets helps professionals choose the right mapping data for their work.