May 2024

This release note provides information about the latest release of OS MasterMap (OSMM) Topography Layer, released to customers on 13th May 2024.

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 LayerCount on 14/03/2024 (Current release)Count on 25/04/2024 (Current release)

Total Feature Count

507 879 548

508 329 170

Count of Topo Area

127 035 158

127 146 339

Count of Topo Line

349 942 731

350 253 247

Count of Topo Point

4 375 415

4 385 721

Count of Topo Bline

532 572

532 257

Count of Topo CartoSym

3 778 000

3 788 842

Count of Topo CartoTxt

22 215 672

22 222 764

Total Count of Deletes

363 259

387 625

Count of Topo Area deletions

75 296

78 038

Count of Topo Line deletions

253 444

277 326

Count of Topo Point deletions

4 059

3 039

Count of Topo Bline deletions

561

533

Count of Topo CartoSymcc deletions

8 953

6 393

Count of Topo CartoTxtcc deletions

20 946

22 296

Total Count of Inserts

866 957

837 247

Count of Topo Area inserts

198 781

189 219

Count of Topo Line inserts

595 718

587 842

Count of Topo Point inserts

17 417

13 345

Count of Topo Bline inserts

222

218

Count of Topo CartoSym inserts

23 256

17 235

Count of Topo CartoTxt inserts

31 563

29 388

Total Count of Modifications

634 202

736 646

Count of Topo Area Modifications

309 690

369 267

Count of Topo Line Modifications

308 659

353 690

Count of Topo Point Modifications

311

231

Count of Topo Bline Modifications

1 403

2 681

Count of Topo CartoSym Modifications

40

44

Count of Topo CartoTxt Modifications

14 099

10 733

COU Size (bytes)

336 114 289

333 062 363

Discrepancies

In this release 10 minor errors were detected, of which 2 have existed since the previous refresh. All errors are considered to be minor errors. We aim to have all errors resolved prior to the next release as part of ongoing quality improvement.

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 areaMinimum area size for land coverMinimum 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:

TOIDLocation (i.e. XY coordinates)

osgb1000000182286603

339097.4, 551740.35

osgb5000005285000934

459029.88, 402617.33

osgb1000002318155560

533464.054, 122925.909

osgb1000000302327200

207276.41, 691450.97

osgb5000005297224912

430701.235, 346985.231

osgb1000002081333910

596419.64, 208356.555

Next release

The next release of OS MasterMap Topography Layer is scheduled for 24th June 2024.

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 one.

5km tileOS grid referenceCoordinates (OSGB36)

NS4505

NS 47825 05240

247790.7,605224.0

TOIDs for example one.

OSMM Topography Layer (July 2022)OSMM Topography Layer (August 2022)

osgb1000000316775097

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 two.

5km tileOS grid referenceCoordinates (OSGB36)

NX3540

NX 37464 41871

237419, 541979

TOIDs for example two.

OSMM Topography Layer (August 2022)OSMM Topography Layer (October 2022)

osgb1000000318639911

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 three.

5km tileOS grid referenceCoordinates (OSGB36)

NX6550

NX 68975 51146

268968, 551139

TOIDs for example three.

OSMM Topography Layer (August 2022)OSMM Topography Layer (October 2022)

osgb1000000319079420

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):

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