October 2025
This release note provides information about the latest release of OS MasterMap (OSMM) Topography Layer, released to customers on 13 October 2025.
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.
Total Feature Count
514 974 777
515 614 618
Count of Topo Area
128 857 321
129 018 023
Count of Topo Line
355 019 217
355 475 070
Count of Topo Point
4 442 738
4 455 077
Count of Topo Bline
522 334
520 905
Count of Topo CartoSym
3 832 769
3 845 014
Count of Topo CartoTxt
22 300 398
22 300 529
Total Count of Deletes
364 981
727 014
Count of Topo Area deletions
68 250
135 551
Count of Topo Line deletions
257 280
530 546
Count of Topo Point deletions
6 140
6 315
Count of Topo Bline deletions
1 361
2 034
Count of Topo CartoSym deletions
5 941
7 229
Count of Topo CartoTxt deletions
26 009
45 339
Total Count of Inserts
750 969
1 366 855
Count of Topo Area inserts
163 855
296 253
Count of Topo Line inserts
529 801
986 399
Count of Topo Point inserts
15 441
18 654
Count of Topo Bline inserts
387
605
Count of Topo CartoSym inserts
16 473
19 475
Count of Topo CartoTxt inserts
25 012
45 474
Total Count of Modifications
641 886
1 274 983
Count of Topo Area Modifications
284 886
635 899
Count of Topo Line Modifications
298 650
620 168
Count of Topo Point Modifications
24 375
1 177
Count of Topo Bline Modifications
1 216
2 063
Count of Topo CartoSym Modifications
23 279
66
Count of Topo CartoTxt Modifications
9 439
15 610
COU Size (bytes)
307 806 216
511 583 092
Changed TOIDs
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:
osgb5000005327045938
135607.22, 838021.44
osgb5000005254562323
402207.598, 436130.472
osgb5000005328202865
500672.771, 408132.615
osgb5000005328887766
285531.727, 884960.194
osgb1000002102358127
337025.6, 427481.95
osgb5000005135183472
517746.541
Discrepancies
In this release 36 errors were detected, of which, 14 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.
Next release
The next release of OS MasterMap Topography Layer is scheduled for 24 November 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
Urban
0.1hectares (ha) (1 000m²)
5m
Rural
0.1hectares (ha) (1 000m²)
10m
Mountain and moorland
1.0hectares (ha) (10 000m²)
10m
New land cover specification
Urban
0.1hectares (ha) (1 000m²)
5m
Rural
0.1hectares (ha) (1 000m²)
5m*
Mountain and moorland
0.1hectares (ha) (1 000m²)*
5m*
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.
Example one
Location of example area one:
NS4505
NS 47825 05240
247790.7, 605224.0
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:
Data before the rural land cover specification refinement update (OSMM Topography Layer – July 2022):
Data after the rural land cover specification refinement update (OSMM Topography Layer – August 2022):
Example two
Location of example area two:
NX3540
NX 37464 41871
237419, 541979
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:
Data before the rural land cover specification refinement update (OSMM Topography Layer – August 2022):
Data after the rural land cover specification refinement update (OSMM Topography Layer – October 2022):
Example three
Location of example area three:
NX6550
NX 68975 51146
268968, 551139
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:
Data before the rural land cover specification refinement update (OSMM Topography Layer – August 2022):
Data after the rural land cover specification refinement update (OSMM Topography Layer – October 2022):
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