November 2024

This release note provides information about the latest release of OS MasterMap (OSMM) Topography Layer, released to customers on 04 November 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 05/09/2024 (Previous release)	Count on 17/10/2024 (Current release)
Total Feature Count	510 067 246	510 670 422
Count of Topo Area	127 597 512	127 758 433
Count of Topo Line	351 522 233	351 963 619
Count of Topo Point	4 390 130	4 391 190
Count of Topo Bline	527 717	524 557
Count of Topo CartoSym	3 785 178	3 780 899
Count of Topo CartoTxt	22 244 476	22 251 724
Total Count of Deletes	562 062	666 186
Count of Topo Area deletions	112 920	138 007
Count of Topo Line deletions	420 657	496 634
Count of Topo Point deletions	2 285	1 941
Count of Topo Bline deletions	3 344	3 858
Count of Topo CartoSym deletions	7 463	7 484
Count of Topo CartoTxt deletions	15 393	18 262
Total Count of Inserts	1 099 911	1 269 362
Count of Topo Area inserts	255 035	298 928
Count of Topo Line inserts	816 716	938 020
Count of Topo Point inserts	3 588	3 001
Count of Topo Bline inserts	444	698
Count of Topo CartoSym inserts	3 699	3 205
Count of Topo CartoTxt inserts	20 429	25 510
Total Count of Modifications	1 095 471	1 257 214
Count of Topo Area Modifications	550 327	643 905
Count of Topo Line Modifications	524 077	597 362
Count of Topo Point Modifications	262	275
Count of Topo Bline Modifications	7 426	2 456
Count of Topo CartoSym Modifications	18	53
Count of Topo CartoTxt Modifications	13 361	13 163
COU Size (bytes)	479 107 436	543 866 589

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)
osgb5000005336454207	236466.509, 628118.225
osgb5000005196539006	329800.731, 477434.786
osgb5000005283135322	507039.113, 375158.152
osgb1000000381134706	128427.853, 919654.391
osgb1000000223021238	333046.984, 476824.072
osgb1000002503313612	518198.08, 452626.12

Discrepancies

In this release 7 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 16 December 2024.

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.

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).