January 2026

This release note provides information about the latest release of OS MasterMap (OSMM) Topography Layer, released to customers on 06 January 2026.

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 06/11/2025 (Last Release)	Count on 11/12/2025 (This Release)
Total Feature Count	516 255 739	516 731 189
Count of Topo Area	129 179 335	129 299 175
Count of Topo Line	355 932 638	356 273 836
Count of Topo Point	4 462 725	4 466 384
Count of Topo Bline	520 570	520 602
Count of Topo CartoSym	3 854 066	3 859 375
Count of Topo CartoTxt	22 306 405	22 311 817
Total Count of Deletes	836 866	598 529
Count of Topo Area deletions	162 006	113 839
Count of Topo Line deletions	612 392	437 808
Count of Topo Point deletions	6 892	4 995
Count of Topo Bline deletions	943	281
Count of Topo CartoSym deletions	5 155	2 984
Count of Topo CartoTxt deletions	49 478	38 622
Total Count of Inserts	1 477 987	1 073 979
Count of Topo Area inserts	323 318	233 679
Count of Topo Line inserts	1 069 960	779 006
Count of Topo Point inserts	14 540	8 654
Count of Topo Bline inserts	608	313
Count of Topo CartoSym inserts	14 207	8 293
Count of Topo CartoTxt inserts	55 354	44 034
Total Count of Modifications	1 407 831	1 038 366
Count of Topo Area Modifications	715 622	527 931
Count of Topo Line Modifications	673 769	496 225
Count of Topo Point Modifications	1 110	1 161
Count of Topo Bline Modifications	1 450	404
Count of Topo CartoSym Modifications	54	151
Count of Topo CartoTxt Modifications	15 826	12 494
COU Size (bytes)	625 627 136	464 904 192

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:

TOID	Location (i.e. XY Coordinates)
osgb1000002017442067	317125.257, 668211.235
osgb1000000396384131	190481.79, 232279.2
osgb1000002051913976	449509.85, 505435.69
osgb1000000288748397	218600.34, 959309.68
osgb5000005336944433	261011.67, 193349.099
osgb1000002036654488	364563.28, 526860.35

Discrepancies

In this release 35 errors were detected, of which, 21 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 16 February 2026.