March 2026
This release note provides information about the latest release of OS MasterMap (OSMM) Topography Layer, released to customers on 30 March 2026.
Last updated
Was this helpful?
This release note provides information about the latest release of OS MasterMap (OSMM) Topography Layer, released to customers on 30 March 2026.
Some customers may see an increase in Change-Only Updates (COU). This is as a result of improvements being made to the accuracy of position attributes rather than the addition of new physical features. These updates have been rolled out for Scotland, with similar updates for England and Wales to follow in future releases.
For more information on this recent update see the Product Announcements page.
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
517 279 866
517 764 300
Count of Topo Area
129 436 199
129 557 449
Count of Topo Line
356 666 805
357 013 181
Count of Topo Point
4 469 251
4 471 108
Count of Topo Bline
520 431
520 000
Count of Topo CartoSym
3 859 805
3 860 384
Count of Topo CartoTxt
22 327 375
22 342 178
Total Count of Deletes
678 764
603 688
Count of Topo Area deletions
134 834
121 842
Count of Topo Line deletions
492 827
451 542
Count of Topo Point deletions
3 157
2 088
Count of Topo Bline deletions
527
710
Count of Topo CartoSym deletions
2 983
2 128
Count of Topo CartoTxt deletions
44 436
25 378
Total Count of Inserts
1 227 441
1 621 570
Count of Topo Area inserts
271 858
776 481
Count of Topo Line inserts
885 796
797 918
Count of Topo Point inserts
6 024
3 945
Count of Topo Bline inserts
356
279
Count of Topo CartoSym inserts
3 413
2 766
Count of Topo CartoTxt inserts
59 994
40 181
Total Count of Modifications
1 158 022
3 488 611
Count of Topo Area Modifications
590 892
533 389
Count of Topo Line Modifications
549 034
2 937 973
Count of Topo Point Modifications
402
650
Count of Topo Bline Modifications
611
677
Count of Topo CartoSym Modifications
32
59
Count of Topo CartoTxt Modifications
17 051
15 863
COU Size (bytes)
514 400 256
538 158 030
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:
osgb5000005332319812
304055.7, 713415.97
osgb1000002102502990
334462.68, 407435.3
osgb5000005210518090
552998.95, 186435.15
osgb1000000384343140
141793.136, 851689.296
osgb5000005305465954
411421.086, 427814.947
osgb5000005192059097
559706.5, 98008.19
In this release 32 errors were detected, of which, 10 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 11 May 2026.
Last updated
Was this helpful?
Was this helpful?