# May 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 12/03/2026 (Last Release)	Count on 23/04/2026 (This Release)
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

## 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) | | -------------------- | ------------------------------ | | 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 | ## Discrepancies 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. ## Next release The next release of OS MasterMap Topography Layer is scheduled for **22 June 2026**. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.os.uk/os-downloads/products/maps-and-imagery-portfolio/os-mastermap-topography-layer/release-notes/may-2026.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.