May 2026
This release note provides information about the latest release of OS MasterMap (OSMM) Topography Layer, released to customers on 11 May 2026.
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This release note provides information about the latest release of OS MasterMap (OSMM) Topography Layer, released to customers on 11 May 2026.
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
517 764 300
518 173 961
Count of Topo Area
129 557 449
129 661 244
Count of Topo Line
357 013 181
357 302 510
Count of Topo Point
4 471 108
4 471 682
Count of Topo Bline
520 000
518 292
Count of Topo CartoSym
3 860 384
3 859 509
Count of Topo CartoTxt
22 342 178
22 360 724
Total Count of Deletes
603 688
347 562
Count of Topo Area deletions
121 842
64 297
Count of Topo Line deletions
451 542
235 690
Count of Topo Point deletions
2 088
1 197
Count of Topo Bline deletions
710
1 968
Count of Topo CartoSymcc deletions
2 128
2 541
Count of Topo CartoTxtcc deletions
25 378
41 869
Total Count of Inserts
1 621 570
757 223
Count of Topo Area inserts
776 481
168 092
Count of Topo Line inserts
797 918
525 019
Count of Topo Point inserts
3 945
1 771
Count of Topo Bline inserts
279
260
Count of Topo CartoSym inserts
2 766
1 666
Count of Topo CartoTxt inserts
40 181
60 415
Total Count of Modifications
3 488 611
566 286
Count of Topo Area Modifications
533 389
264 713
Count of Topo Line Modifications
2 937 973
264 101
Count of Topo Point Modifications
650
471
Count of Topo Bline Modifications
677
1 046
Count of Topo CartoSym Modifications
59
30
Count of Topo CartoTxt Modifications
15 863
35 925
COU Size (bytes)
538 158 030
326 483 968
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:
osgb5000005329555752
183338, 893733.5
osgb1000002092258122
245944.735, 235202.037
osgb5000005333384452
365332.651, 189494.244
osgb5000005249618703
257893.98,905598.41
osgb5000005114905723
299582.534,250216.783
osgb5000005336550317
458931.349, 522938.326
In this release 9 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.
The next release of OS MasterMap Topography Layer is scheduled for 22 June 2026.
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