September 2025
This release note provides information about the latest release of OS MasterMap (OSMM) Topography Layer, released to customers on 03 September 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
514 588 789
514 974 777
Count of Topo Area
128 761 716
128 857 321
Count of Topo Line
354 746 696
355 019 217
Count of Topo Point
4 433 437
4 442 738
Count of Topo Bline
523 308
522 334
Count of Topo CartoSym
3 822 237
3 832 769
Count of Topo CartoTxt
22 301 395
22 300 398
Total Count of Deletes
400 830
364 981
Count of Topo Area deletions
84 645
68 250
Count of Topo Line deletions
289 224
257 280
Count of Topo Point deletions
4 199
6 140
Count of Topo Bline deletions
366
1 361
Count of Topo CartoSym deletions
3 823
5 941
Count of Topo CartoTxt deletions
18 573
26 009
Total Count of Inserts
987 946
750 969
Count of Topo Area inserts
231 465
163 855
Count of Topo Line inserts
704 591
529 801
Count of Topo Point inserts
13 317
15 441
Count of Topo Bline inserts
382
387
Count of Topo CartoSym inserts
14 794
16 473
Count of Topo CartoTxt inserts
23 397
25 012
Total Count of Modifications
786 151
641 886
Count of Topo Area Modifications
372 940
284 907
Count of Topo Line Modifications
396 665
298 650
Count of Topo Point Modifications
1 046
24 375
Count of Topo Bline Modifications
1 997
1 216
Count of Topo CartoSym Modifications
74
23 279
Count of Topo CartoTxt Modifications
13 429
9 439
COU Size (bytes)
388 693 359
307 806 216
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:
osgb5000005341025220
278344.291, 850609.011
osgb1000000092972540
435318.288, 442253.38
osgb5000005295456368
502657.852, 458833.678
osgb1000000387467333
173292.659, 779312.414
osgb5000005340979623
343089.3, 457645
osgb5000005235181584
525890.283, 435956.248
Discrepancies
In this release 14 errors were detected, of which, of which 11 are new errors. 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 13 October 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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