> For the complete documentation index, see [llms.txt](https://docs.os.uk/os-downloads/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.os.uk/os-downloads/products/maps-and-imagery-portfolio/1-50-000-scale-colour-raster/1-50-000-scale-colour-raster-overview/product-details.md).
# Product details
## Source and scale of the product
1:50 00 Scale Colour Raster is derived from the source data used to create its graphic counterpart, the OS Landranger Map series. Generalisation is used to emphasise, simplify, select and sometimes omit features to produce a cartographic representation of the landscape at a scale of 1:50 000.
The nominal scale of the product is 1:50 000, but the recommended minimum-to-maximum scale range is 1:15 000 to 1:60 000 scale. It is best viewed between 1:20 000 and 1:50 000 scale.
## Coordinate reference system
1:50 000 Scale Colour Raster is available in National Grid coordinates, which are expressed in metres relative to an origin set to a point west of the Isles of Scilly. These coordinates can easily be spatially related to other surveys, drawings, datasets or Ordnance Survey products.
A [general introductory guide to the British National Grid (BNG)](https://getoutside.ordnancesurvey.co.uk/guides/beginners-guide-to-grid-references/) is available on the OS website.
## Coverage
Coverage is Great Britain.
1:50 000 Scale Raster is supplied in standard 20km by 20km tiles aligned to the National Grid.
## Product revision programme
1:50 000 Scale Colour Raster is updated via a revision programme. The revision programme mirrors that of the OS Landranger Map series, and is determined by assessing the following factors:
* Known surveyed change
* Change intelligence gathered from a range of sources
* How long it's been since an area was last revised
Priority is given to prestige sites categorised as significant items of change, such as major road construction projects. Significant items of surveyed change relevant to the scale are captured during the revision programme.
Where a line feature ends by intersecting the tile edge, it is matched with its corresponding feature on the adjacent tile so that both features end on the same unique coordinate. The representation of detail across the tile edge will be of a cartographically acceptable standard when plotted or displayed at scale.
## Product update schedule
1:50 000 Scale Colour Raster is supplied to customers quarterly in March, June, September and December, incorporating any updates made by the revision programme.
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