July 2025
This release note provides information about the latest release of OS MasterMap (OSMM) Topography Layer, released to customers on 30 July 2025.
For awareness, users may notice some changes in this release (30 July 2025) which have been outlined below. These issues have been present in some customer supplies of the GML format between 28 June 2025 and Friday 01 August.
If the changes have impacted you and you would like a resupply, please contact us via the website or email us at [email protected].
Broken download links for OS MasterMap Topography Layer GML 5km2 tile download orders
Customer Topography 5km2 tile download orders in GML format, supplied from 30 July 2025 to 12 August 2025 contain broken download links. As a result, an error message will be displayed saying there is no data available to download.
This issue was fixed on 12 August 2025 and new orders after this date will not be affected. Any customers impacted by this issue will be contacted directly. We aim to resupply all orders by 15 August 2025.
Where customers have placed an initial one off order, we advise reordering the data or contacting our fulfilment team (email us at [email protected]) to request a resupply. We apologise for any inconvenience this has caused.
Issues affecting Geographically Chunked GML supply
Issue 1: osgb:BoundedBy Tag
BoundedBy is the minimum bounding rectangle (MBR) that encloses all features actually returned in the dataset, not just the area requested. It provides metadata about the spatial extent of the returned data, which may be smaller or larger than the queryExtent, depending on what features exist in the dataset. For example, if your queryExtent includes a large area but only a few features are returned in a small corner, the boundedBy will reflect just that smaller area.
This metadata tag was found to be missing in some GeoChunk GML files in this release of OS MasterMap Topography Layer.
Issue 2: standalone=’yes’
This is usually found in the opening line of all geographically chunked GML files for OS MasterMap Topography Layer, but is missing from this release for some orders.
The tag of standalone=’yes’ means the GML does not rely on any external DTD (Document Type Definition). All the information needed to parse and validate the GML is contained within the file itself.
Issues affecting Non-Geographically Chunked GML COU (change only update) supply
Issue 3: 'queryChangeSinceDate' tag
This tag is usually published in OSMM Topography Layer COU to inform users of when the changes apply from, but it is missing from some customer data supplies in this release of the GML file. It can be used as part of the COU load process.
The fix for this issue has been implemented and is being thoroughly tested before being deployed to our live systems. Once testing has passed the distribution of customer orders for non-geographically chunking product variation orders will be resumed.
Future releases of OS MasterMap Topography Layer
For this release, the publication date was 30 July 2025 and the extraction date was 10 July 2025.
There will be no impact on future release cycles. The next release date for OS MasterMap Topography Layer will be 01 September 2025 as scheduled on our product refresh dates page, with an extraction date of 14 August 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
514 001 673
514 588 789
Count of Topo Area
128 614 896
128 761 716
Count of Topo Line
354 331 329
354 746 696
Count of Topo Point
4 424 319
4 433 437
Count of Topo Bline
523 292
523 308
Count of Topo CartoSym
3 811 266
3 822 237
Count of Topo CartoTxt
22 296 571
22 301 395
Total Count of Deletes
390 811
400 830
Count of Topo Area deletions
85 937
84 645
Count of Topo Line deletions
285 889
289 224
Count of Topo Point deletions
3 240
4 199
Count of Topo Bline deletions
280
366
Count of Topo CartoSym deletions
3 869
1 762
Count of Topo CartoTxt deletions
11 596
18 573
Total Count of Inserts
1 059 781
987 946
Count of Topo Area inserts
250 612
231 465
Count of Topo Line inserts
749 761
704 591
Count of Topo Point inserts
18 904
13 317
Count of Topo Bline inserts
176
382
Count of Topo CartoSym inserts
20 444
14 803
Count of Topo CartoTxt inserts
19 884
23 397
Total Count of Modifications
849 996
786 151
Count of Topo Area Modifications
403 456
372 940
Count of Topo Line Modifications
433 798
396 665
Count of Topo Point Modifications
857
1 046
Count of Topo Bline Modifications
883
1 997
Count of Topo CartoSym Modifications
37
86
Count of Topo CartoTxt Modifications
10 965
13 429
COU Size (bytes)
416 198 799
388 693 359
CartoSym counts were added to this release note on 07 August 2025. All other counts including total counts and COU size have not changed since initial publication.
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:
osgb5000005298892943
123804.745, 860066.192
osgb5000005255435016
331562.51, 496930.79
osgb1000000013752053
508667.053, 431390.732
osgb5000005336494913
310555.05, 968584.1
osgb1000000083528931
470646.99, 465628.53
osgb1000002503340685
532497.94, 406843.42
Discrepancies
In this release, 356 errors were detected, of which 99 are new errors. These are all considered to be minor errors. There are no known major errors present.
This spike in error counts has been investigated, and the cause found to be 'slitheres' between polygons and extra vertices where lines intersect. These will not be visible in product, and should not impact the customer.
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 01 September 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):

Last updated
Was this helpful?