2 to 10 year cycles overtake 5 and 10 year cycles

The following explain the previous and new approach to cyclic revision.  With the new 2 - 10 year programme for cyclic revision, in the majority of cases, rural mapping will be revised as or more frequently than it was before.  There will be a relatively small number of areas that will be revised less frequently.  However, these areas will still be updated by continuous revision and therefore significant types of change such as new buildings and roads will surveyed within 6 months of the change happening in the real world. 

Previous approach: 5 and 10 year cycle

Since 1995, Ordnance Survey's approach to undertaking rural revision has been to complete 5 year cyclic sweeps where every 1:2500 rural tile is visited in each cycle.  Also under this programme, all 1:10,000 mountain and moorland tiles were visited in the 10 years spanning the two cycles.

Consequently, although this approach clearly identified all the tiles that needed revision, it did mean that areas where significant amounts of change had occurred were not given any scheduling priority over those areas with little or no change.  In addition, the gap between visits on any given tile could be longer than 5 years (up to 8 years) depending on where the tile was scheduled in each of the cycles.

New approach: 2 - 10 year cycles

This year sees the introduction of a new approach to cyclic revision.  A new sweep programme has been developed that is driven by the amount and speed at which change has occurred on the ground. Ordnance Survey has made investment in improved sources of intelligence about change in the landscape, through finding new available sources of variation for a broader range of real world features.

The new programme for cyclic revision therefore divides up Great Britain according to the amount of change that is anticipated per geographical area.  These areas are then assigned a revision frequency.  These frequencies are constantly reviewed using the most up to date change intelligence information.  The new programme also makes attempts to construct the sweeps into more logical areas than in the previous situation.  Sweep areas will be more closely aligned with local authority areas.

The result is the creation of a new programme, where every area will have the following revision frequency assigned to it:

• Areas of rapid and significant change will be swept every 2-3 years
• Areas of moderate rates of change will be swept every 4-7 years
• Areas of little change will be swept every 8-10 years

For example, an area surrounding a main transport commuter route where development is happening regularly will be swept every 2-3 years, whereas a remote moorland area, where development and even natural change is limited, will be swept every 8 - 10 years. 

Hence, under the new revision regime, all areas of Great Britain will be revised at least once every ten years, with more populated areas being revised much more frequently.  In general, 70% of rural and moorland areas in England will be revised every 4 years and 100% of those areas of Wales will be revised within 8 years.  All of Scotland will be revised within a 10 year cycle, with 56% being revised every 8 years, which is an improvement to the revision cycle within Scotland under the revision regime funded by the NIMSA agreement.