April 2025
This release note provides information about the latest release of OS MasterMap (OSMM) Topography Layer, released to customers on 28 April 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
512 632 961
513 332 703
Count of Topo Area
128 273 981
128 450 221
Count of Topo Line
353 377 395
353 867 457
Count of Topo Point
4 394 656
4 408 655
Count of Topo Bline
523 727
523 396
Count of Topo CartoSym
3 780 848
3 794 691
Count of Topo CartoTxt
22 282 354
22 288 283
Total Count of Deletes
814 144
431 326
Count of Topo Area deletions
175 473
93 105
Count of Topo Line deletions
616 657
312 299
Count of Topo Point deletions
2 235
2 968
Count of Topo Bline deletions
707
581
Count of Topo CartoSym deletions
3 024
3 343
Count of Topo CartoTxt deletions
16 048
19 030
Total Count of Inserts
1 636 249
1 131 068
Count of Topo Area inserts
391 553
269 345
Count of Topo Line inserts
1 207 990
802 361
Count of Topo Point inserts
4 284
16 967
Count of Topo Bline inserts
419
250
Count of Topo CartoSym inserts
3 635
17 186
Count of Topo CartoTxt inserts
28 368
24 959
Total Count of Modifications
1 640 594
942 705
Count of Topo Area Modifications
826 746
454 719
Count of Topo Line Modifications
782 736
465 942
Count of Topo Point Modifications
262
708
Count of Topo Bline Modifications
1 304
2 338
Count of Topo CartoSym Modifications
21
40
Count of Topo CartoTxt Modifications
29 525
18 958
COU Size (bytes)
675 322 893
455 622 555
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:
osgb1000000293846487
293567.52, 848031.49
osgb1000000259708705
333269.921, 305089.332
osgb5000005340644478
527769.955, 320398.718
osgb1000000381025439
112917.344, 929393.05
osgb1000000082652189
479651.032, 452509.699
osgb5000005126254302
505357.85, 432352.5
Discrepancies
In this release 19 errors were detected, of which, 1 has 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 09 June 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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