Site Finder: The Best Sites in an Area

The site finder is multi-criteria evaluation, written down so the same inputs always give the same answer.

1. Cover the search area with a grid of 100 m cells in British National Grid.
2. Rule out every cell whose centre is inside a protected designation or the flood zones you chose. Always ruled out: Sites of Special Scientific Interest, Special Areas of Conservation, Special Protection Areas, Ramsar sites, National Nature Reserves, ancient woodland, scheduled monuments, registered parks and gardens, registered battlefields and World Heritage Sites. An exclusion is never applied from a partial download.
3. Score each remaining cell from 0 to 1 on each criterion. For a distance, the score falls in a straight line from 1 at the full-score distance to 0 at the zero-score distance (table below). Deprivation deciles and population densities are scaled from 0 to 1.
4. Weight each score by its importance and add them up (a weighted linear combination). Weights can also come from a pairwise comparison matrix (the analytic hierarchy process), with its consistency ratio reported.
5. Take the best 5% of cells and grow candidate sites from the best cell outwards through touching cells, up to the largest size; drop sites under the smallest size; rank the sites by their mean score.
6. Test the ranking: 500 runs with each weight moved at random by up to 20% either way, re-ranking the sites each time. A fixed random seed means the test repeats exactly.