April 2024

This release note provides information about the latest release of OS MasterMap (OSMM) Topography Layer, released to customers on 02 April 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 01/02/2024 (Previous release)	Count on 14/03/2024 (Current release)
Total Feature Count	507 375 850	507 879 548
Count of Topo Area	126 911 673	127 035 158
Count of Topo Line	349 600 457	349 942 731
Count of Topo Point	4 362 057	4 375 415
Count of Topo Bline	532 911	532 572
Count of Topo CartoSym	3 763 697	3 778 000
Count of Topo CartoTxt	22 205 055	22 215 672
Total Count of Deletes	352 971	363 259
Count of Topo Area deletions	72 340	75 296
Count of Topo Line deletions	246 393	253 444
Count of Topo Point deletions	4 698	4 059
Count of Topo Bline deletions	433	561
Count of Topo CartoSymcc deletions	11 208	8 953
Count of Topo CartoTxtcc deletions	17 899	20 946
Total Count of Inserts	811 142	866 957
Count of Topo Area inserts	180 007	198 781
Count of Topo Line inserts	551 663	595 718
Count of Topo Point inserts	21 692	17 417
Count of Topo Bline inserts	353	222
Count of Topo CartoSym inserts	29 505	23 256
Count of Topo CartoTxt inserts	27 922	31 563
Total Count of Modifications	600 677	634 202
Count of Topo Area Modifications	294 892	309 690
Count of Topo Line Modifications	291 597	308 659
Count of Topo Point Modifications	326	311
Count of Topo Bline Modifications	628	1 403
Count of Topo CartoSym Modifications	132	40
Count of Topo CartoTxt Modifications	13 102	14 099
COU Size (bytes)	386 470 897	336 114 289

Discrepancies

9 minor errors were detected, which is 2 more than were found in the last refresh. Of these 9 errors, 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 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)
osgb5000005109728428	322926.508, 704955.071
oosgb5000005252408974	396225, 4754643
osgb1000000030598131	504443.618, 242017.376
osgb1000000293839535	203531.7, 862031.28
osgb5000005299999425	406660.07, 436264.33
osgb5000005243520249	505688.732, 484331.45

Next release

The next release of OS MasterMap Topography Layer is scheduled for 13 May 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 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).