Constraint layers
Screening comparison
Each site starts at 100 and loses points for the share of its area that falls inside each constraint layer, using the project's proposed layer weights.
Constraint screening score
Higher means fewer mapped constraintsConstraint matrix
% of site area inside each layerTheme profile
Illustrative · themes not yet connected to dataEnvironment and landscape come from the screening above. Transport, community, economy and housing scores are placeholders that show where accessibility and infrastructure evidence will sit. Move the theme weights to see the indicative order change.
Theme weights
Data coverage
A layer only counts where its verified coverage contains the whole site. A missing or unverified layer is reported as unknown and never treated as clear.
How a site is screened
Four steps, each one recorded so the result can be checked and repeated.
Draw the red line
Draw or import each boundary in WGS84. Geometry is checked for validity and must sit between 1 m² and 20,000 ha.
Project to BNG
Sites and layers are projected to British National Grid (EPSG:27700) so areas are measured in true hectares.
Intersect each layer
A spatial index finds every touching feature. Overlaps are clipped and unioned so nothing is counted twice.
Compare and report
Overlap hectares and percentages feed a weighted score, only when every layer has verified coverage for every site.
Constraint layer weights
Total 100 · proposed by the projectScore = Σ weight × (1 − overlap %). A site with no mapped constraint scores 100. This is a constraint screen, not an overall sustainability rank.
Statutory basis
The themes follow the topics in Schedule 2 of the SEA Regulations 2004, the NPPF and government SA/SEA guidance. Data comes from planning.data.gov.uk, the Environment Agency, Natural England and Historic England.
What this does not decide
It does not judge significance, buffers, cumulative effects, mitigation or reasonable alternatives. "No intersection" means no mapped feature in that data snapshot, not an absence of effects. It is preliminary evidence support for an appraisal, not a statutory Sustainability Appraisal, SEA, HRA or EIA.
Six themes, 24 indicators
Proposed national framework v0.1Still to do before national launch
From the build notes- Licensed national downloads for all nine layers, refreshed automatically with checksums and publisher dates.
- Coverage checks against the England boundary: gaps, schema changes, invalid and duplicate features.
- Attribute rules for each layer, such as Flood Zone 2 vs 3 and ALC grade, plus buffer distances.
- Travel-time accessibility to schools, health, jobs and rail from authoritative datasets.
- Council-specific methodology, policy versioning and a professional review step.
- PostGIS storage, accounts, job queue, audit log, monitoring and rate limits.
- Independent verification of outputs and a legal review before commercial use.