December 2024

This release note provides information about the latest release of OS MasterMap (OSMM) Topography Layer, released to customers on 16 December 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 Layer	Count on 17/10/2024 (Current release)	Count on 28/11/2024 (Current release)
Total Feature Count	510 670 422	511 231 453
Count of Topo Area	127 758 433	127 905 526
Count of Topo Line	351 963 619	352 369 150
Count of Topo Point	4 391 190	4 391 725
Count of Topo Bline	524 557	524 140
Count of Topo CartoSym	3 780 899	3 780 153
Count of Topo CartoTxt	22 251 724	22 260 759
Total Count of Deletes	666 186	680 332
Count of Topo Area deletions	138 007	142 472
Count of Topo Line deletions	496 634	516 063
Count of Topo Point deletions	1 941	1 952
Count of Topo Bline deletions	3 858	1 080
Count of Topo CartoSym deletions	7 484	3 478
Count of Topo CartoTxt deletions	18 262	15 287
Total Count of Inserts	1 269 362	1 241 363
Count of Topo Area inserts	298 928	289 565
Count of Topo Line inserts	938 020	921 594
Count of Topo Point inserts	3 001	2 487
Count of Topo Bline inserts	698	663
Count of Topo CartoSym inserts	3 205	2 732
Count of Topo CartoTxt inserts	25 510	24 322
Total Count of Modifications	1 257 214	1 226 070
Count of Topo Area Modifications	643 905	624 491
Count of Topo Line Modifications	597 362	587 411
Count of Topo Point Modifications	275	287
Count of Topo Bline Modifications	2 456	767
Count of Topo CartoSym Modifications	53	22
Count of Topo CartoTxt Modifications	13 163	13 092
COU Size (bytes)	543 866 589	530 999 702

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)
osgb5000005336348561	303087.887, 857162.222
osgb5000005331742080	360972.262, 394804.694
osgb1000001644059895	515401.35, 461688.52
osgb1000000288040716	216861.731, 933944.811
osgb1000000223011430	331477.816, 481794.328
osgb5000005256265197	559369.893, 313898.605

Discrepancies

In this release 5 errors were detected, of which, 2 have 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 03 February 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

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*

Note: 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.

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).