October 2023

This release note provides information about the latest release of OS MasterMap (OSMM) Topography Layer, released to customers on 09 October 2023.

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 10/08/2023 (Previous Release)	Count on 21/09/2023 (Current Release)
Total Feature Count	505 631 081	506 051 882
Count of Topo Area	126 426 540	126 561 435
Count of Topo Line	348 477 006	348 736 616
Count of Topo Point	4 311 133	4 321 409
Count of Topo Bline	534 114	533 621
Count of Topo CartoSym	3 712 020	3 722 356
Count of Topo CartoTxt	22 170 268	22 176 445
Total Count of Deletes	580 807	552 193
Count of Topo Area deletions	93 938	90 968
Count of Topo Line deletions	440 874	413 319
Count of Topo Point deletions	4 722	4 058
Count of Topo Bline deletions	689	1 023
Count of Topo CartoSymcc deletions	10 421	9 835
Count of Topo CartoTxtcc deletions	30 163	32 990
Total Count of Inserts	963 518	972 994
Count of Topo Area inserts	218 909	225 863
Count of Topo Line inserts	672 774	672 929
Count of Topo Point inserts	14 794	14 334
Count of Topo Bline inserts	296	530
Count of Topo CartoSym inserts	21 966	20 171
Count of Topo CartoTxt inserts	34 779	39 167
Total Count of Modifications	941 944	833 584
Count of Topo Area Modifications	442 081	378 432
Count of Topo Line Modifications	479 273	430 672
Count of Topo Point Modifications	339	319
Count of Topo Bline Modifications	665	1 190
Count of Topo CartoSym Modifications	173	103
Count of Topo CartoTxt Modifications	19 413	22 868
COU Size (bytes)	418 831 687	413 944 082

New formats available

Alongside GML format, OSMM Topography Layer is also available in GeoPackage and vector tiles formats (from March 2023). Please see the Getting Started with GeoPackage and Getting Started with Vector Tiles guides for more information on using these new formats. The product is supplied as an online download. You can download data in its various formats from the OS Data Hub.

Discrepancies

• 48 minor errors were detected, which is 12 more than the 36 errors found in the last refresh. Of these errors, 4 have existed since the previous refresh – these are minor issues caused by conflict (where the geometry of adjacent feature has not been updated to match), but there are no visible issues.

• An issue has been identified whereby post offices are being incorrectly attributed or deleted due to data misinterpretation. In the previous release over 1 100 reclassified / deleted post offices were noted. There are 966 of these errors remaining in the October 2023 release. This may result in the carto text ‘Post Office’ or ‘PO’ missing from OSMM Topography Layer. A solution is currently being investigated for this issue and we aim to rectify it as soon as possible.

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

Geographic Area	Minimum Area Size for Land Cover	Minimum Width
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

Geographic Area	Minimum Area Size for Land Cover	Minimum Width
Urban	0.1hectares (ha) (1 000m²)	5m
Rural	0.1hectares (ha) (1 000m²)	5m*
Mountain and moorland	0.1hectares (ha) (1 000m²)*	5m*

The asterisk symbol (*) shows which criteria have been refined.

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.

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)
osgb5000005305675906	266453.432, 660668.531
osgb5000005121024361	297913.54, 337342.3
osgb5000005141832094	530516.838, 268540.61
osgb1000000390737946	140986.634, 699762.657
osgb1000002312456023	271311.2, 318049.66
osgb5000005282543279	614730.487, 257892.756

Next release

The next release of OS MasterMap Topography Layer is scheduled for 20 November 2023.

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:

5km Tile	OS Grid Reference	Coordinates (OSGB36)
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:

Photo of imagery of an area in southern Scotland taken in January 2021 highlighting an area of rural land cover. Provided for comparative purposes to show how the rural land cover specification refinement has altered the data in example area 1.

Data before the rural land cover specification refinement update (OSMM Topography Layer – July 2022):

Screenshot of what the data in example area 1 looked like prior to the rural land cover specification refinement update (July 2022 OS MasterMap Topography Layer data).

Data after the rural land cover specification refinement update (OSMM Topography Layer – August 2022):

Screenshot of what the data in example area 1 looked like after the rural land cover specification refinement update (August 2022 OS MasterMap Topography Layer data).

Example two

Location of example area two:

5km Tile	OS Grid Reference	Coordinates (OSGB36)
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:

Photo of imagery of an area in southern Scotland highlighting an area of rural land cover. Provided for comparative purposes to show how the rural land cover specification refinement has altered the data in example area 2.

Data before the rural land cover specification refinement update (OSMM Topography Layer – August 2022):

Screenshot of what the data in example area 2 looked like prior to the rural land cover specification refinement update (August 2022 OS MasterMap Topography Layer data).

Data after the rural land cover specification refinement update (OSMM Topography Layer – October 2022):

Screenshot of what the data in example area 2 looked like after the rural land cover specification refinement update (October 2022 OS MasterMap Topography Layer data).

Example three

Location of example area three:

5km Tile	OS Grid Reference	Coordinates (OSGB36)
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:

Photo of imagery of an area in southern Scotland highlighting an area of rural land cover. Provided for comparative purposes to show how the rural land cover specification refinement has altered the data in example area 3.

Data before the rural land cover specification refinement update (OSMM Topography Layer – August 2022):

Screenshot of what the data in example area 3 looked like prior to the rural land cover specification refinement update (August 2022 OS MasterMap Topography Layer data).

Data after the rural land cover specification refinement update (OSMM Topography Layer – October 2022):

Screenshot of what the data in example area 3 looked like after the rural land cover specification refinement update (October 2022 OS MasterMap Topography Layer data).