OSMM Topography Layer product count
The following table contains product counts for this release of OSMM Topography Layer data. The dates shown are extraction dates, not release dates.
OSMM Topography Layer
Count on 28/11/2024 (Last release)
Count on 16/01/2025 (Current release)
Count of Topo Area deletions
Count of Topo Line deletions
Count of Topo Point deletions
Count of Topo Bline deletions
Count of Topo CartoSym deletions
Count of Topo CartoTxt deletions
Count of Topo Area inserts
Count of Topo Line inserts
Count of Topo Point inserts
Count of Topo Bline inserts
Count of Topo CartoSym inserts
Count of Topo CartoTxt inserts
Total Count of Modifications
Count of Topo Area Modifications
Count of Topo Line Modifications
Count of Topo Point Modifications
Count of Topo Bline Modifications
Count of Topo CartoSym Modifications
Count of Topo CartoTxt Modifications
Numerous TOIDs (Topographic Identifiers) have changed since the last refresh, resulting in a visual difference in the data. The list below shows a sample of changed TOIDs and their locations that you can use as 'lookup samples' to validate that your latest supply has updated correctly:
TOID
Location (i.e. XY coordinates)
In this release 8 errors were detected, of which, 2 have existed since the previous refresh. These are all considered to be minor errors and there are no major errors present.
We aim to have all errors resolved prior to the next release as part of ongoing quality improvements.
The next release of OS MasterMap Topography Layer is scheduled for 17 March 2025.
Land cover refinement changes
The land cover specification for rural geographies has been refined. The Mountain and Moorland refinement was completed in 2022.
The rural geography updates began capture in May 2022. The initial updates fed through to the July 2022 release of OSMM Topography Layer, with the multi class land cover polygons completed in December 2022. The single class land cover polygons will continue to feed through to product from April 2023.
The following two tables articulate this specification refinement:
Old land cover specification
Geographic Area
Minimum Area Size for Land Cover
Minimum Width
0.1hectares (ha) (1 000m²)
0.1hectares (ha) (1 000m²)
1.0hectares (ha) (10 000m²)
New land cover specification
Geographic Area
Minimum Area Size for Land Cover
Minimum Width
0.1hectares (ha) (1 000m²)
0.1hectares (ha) (1 000m²)
0.1hectares (ha) (1 000m²)*
The land cover specification refinement means that the rural land cover data within OSMM Topography Layer will become more granular, producing a more detailed view made up of smaller more numerous polygons. This provides users with more accurate data that meets each individual’s specific requirements. These changes are purely refinements and do not change the data attribution.
Annex A shows three examples of how the rural land cover refinement is being translated into OSMM Topography Layer.
Annex A: Rural land cover specification refinement examples
Below are three real-world examples of how the rural land cover specification refinement has affected the data within OSMM Topography Layer. The examples showcase three areas in southern Scotland where the specification refinement has broken up one land polygon within the Topographic Area Feature Type into smaller, separate polygons.
Location of example area one:
5km Tile
OS Grid Reference
Coordinates (OSGB36)
TOIDs for example area one:
OSMM Topography Layer (July 2022): osgb1000000316775097
OSMM Topography Layer (August 2022): osgb5000005297485451, osgb5000005297485455, osgb5000005297485456
Source imagery of example area one for comparative purposes:
Photo of imagery of an area in southern Scotland taken in January 2021 highlighting an area of rural land cover. Provided for comparative purposes to show how the rural land cover specification refinement has altered the data in example area 1. Data before the rural land cover specification refinement update (OSMM Topography Layer – July 2022):
Screenshot of what the data in example area 1 looked like prior to the rural land cover specification refinement update (July 2022 OS MasterMap Topography Layer data). Data after the rural land cover specification refinement update (OSMM Topography Layer – August 2022):
Screenshot of what the data in example area 1 looked like after the rural land cover specification refinement update (August 2022 OS MasterMap Topography Layer data). Location of example area two:
5km Tile
OS Grid Reference
Coordinates (OSGB36)
TOIDs for example area two:
OSMM Topography Layer (July 2022): osgb1000000318639911
OSMM Topography Layer (August 2022): osgb1000000318639911, osgb5000005298080383, osgb5000005298080465
Source imagery of example area two for comparative purposes:
Photo of imagery of an area in southern Scotland highlighting an area of rural land cover. Provided for comparative purposes to show how the rural land cover specification refinement has altered the data in example area 2. Data before the rural land cover specification refinement update (OSMM Topography Layer – August 2022):
Screenshot of what the data in example area 2 looked like prior to the rural land cover specification refinement update (August 2022 OS MasterMap Topography Layer data). Data after the rural land cover specification refinement update (OSMM Topography Layer – October 2022):
Screenshot of what the data in example area 2 looked like after the rural land cover specification refinement update (October 2022 OS MasterMap Topography Layer data). Location of example area three:
5km Tile
OS Grid Reference
Coordinates (OSGB36)
TOIDs for example area three:
OSMM Topography Layer (July 2022): osgb1000000319079420
OSMM Topography Layer (August 2022): osgb1000000319079420, osgb5000005298106224
Source imagery of example area three for comparative purposes:
Photo of imagery of an area in southern Scotland highlighting an area of rural land cover. Provided for comparative purposes to show how the rural land cover specification refinement has altered the data in example area 3. Data before the rural land cover specification refinement update (OSMM Topography Layer – August 2022):
Screenshot of what the data in example area 3 looked like prior to the rural land cover specification refinement update (August 2022 OS MasterMap Topography Layer data). Data after the rural land cover specification refinement update (OSMM Topography Layer – October 2022):
Screenshot of what the data in example area 3 looked like after the rural land cover specification refinement update (October 2022 OS MasterMap Topography Layer data). 
