Sources, dates and method

notbad combines saved datasets to help you ask more precise questions about a London location. These are screening estimates and historical records. Each source answers a different question; none establishes whether a particular home is right for you.

Explore and postcode reports answer different questions

Explore starts with all ten conditions disabled. Every enabled condition must match for a place to remain green. Adding a condition can only remove places. Missing walking or crime evidence cannot pass an enabled condition. Missing noise is allowed by the exclusion policy, with quietness explicitly unverified.

The independent postcode report checks all ten criteria using its own profile. It shows both periods for aircraft, road and railway noise; all supported rail lines without the backup requirement; green spaces of at least 2 hectares; all school phases, grades and ungraded schools; all supported supermarket chains; and both shopping types. Walking searches stop at 30 minutes. There is no combined report score.

Noise and Tube proximity

Aircraft uses Defra Round 4, the 2022 mapping edition. Airport activity years vary and are not verified for every airport in this retained supply. Road and railway models use 2021 activity for the 2022 mapping edition, with outdoor receptors at 4 metres. They do not measure sound indoors or predict intermittent events in a particular room.

Daytime covers 07:00–23:00 and nighttime 23:00–07:00. Published road and rail values start at 40 dB day and 35 dB night. A missing reading is not zero. Supplied values strictly below your chosen limit pass the exclusion; equality or above fails. The app's starting thresholds are screening choices, not official quietness limits.

The separate 100-metre Tube setback uses the April 2026 TfL cycling-permission map and mapped Underground tracks, including some tunnels. It is a proximity proxy, not a vibration measurement, depth estimate or guarantee for homes outside the setback.

Walking and destinations

Walking uses retained mapped paths and street connections at 80 metres per minute, with a supported maximum of 30 minutes. Starting positions are approximate; barriers, direction and mapped access affect whether a usable approach exists. A result can remain unknown even when a destination appears close on the basemap. The engine is not a wheelchair-routing service.

Rail access covers Underground, Overground, DLR and Elizabeth line services. It does not include every National Rail service. An absent supported-line result therefore does not establish that an area has no railway station. Optional backup access in Explore requires two different selected line IDs; an interchange may provide both.

A qualifying green space needs a mapped walking path and no explicit access prohibition. Its individual mapped area, allowing for holes, must meet your minimum. Basemap greenery alone is not evidence of public access. Supermarkets use supported full-format mapped chain shops, excluding recognised compact formats. Shopping covers qualifying mapped centres and streets, with access approximations labelled. Current openings, closures and internal shopping journeys are not modelled.

Crime and schools

Crime compares London LSOA 2021 areas using September 2024–August 2026 published Metropolitan Police and City of London records, annualised per 1,000 ONS mid-2024 residents. Five app-derived London bands are not official safety grades. Anti-social behaviour, unlocated records and the incomplete transport-police series are excluded. Busy visitor areas can have high recorded rates relative to their resident populations.

Schools use the GIAS register dated 31 October 2026 and an Ofsted snapshot dated 30 September 2026. Legacy overall grades and new evaluation-area report cards are separate. Only current-URN inspection links are used. Nearby schools and approximate walking times do not establish catchment eligibility, admissions priority, a place or current gate access.

Postcodes, boundaries and privacy

Postcodes come from OS Code-Point Open August 2026, supply 2026.3.0, with Royal Mail updates to 17 July 2026. A postcode is a representative point for several addresses, with approximate positions labelled. The complete retained official Greater London boundary determines membership, independently of postcode districts. The boundary dataset describes 2017 administrative boundaries.

Input and calculations stay in your browser. Search sharing includes filter settings and general map camera only, excluding postcode input, a selected-place marker and location reports. The site has no external analytics or runtime data service.

How the 33 area comparisons were made

Each territory uses three distinct named reference positions from the retained station, green-space, shopping and supermarket catalogs, checked against the complete borough polygon. Selection favours a station near the borough's representative position, a nearby named green space of at least 2 hectares and a shopping site or supermarket. Where a type is absent, another named public catalog position is used. These are illustrative examples, not a random or statistically representative sample of homes.

Every example runs through the same independent report profile as Check mode. Coordinates describe source reference positions, which may be inside a park or site rather than at a public entrance. The table preserves unknown results. Named destinations may cross borough boundaries; proximity is calculated from the reference point without artificially stopping at an administrative boundary.

Catalog counts on area pages count retained reference positions inside that boundary. They do not count all destinations intersecting it, prove current access, or establish a complete real-world inventory. The figures show the saved local basemap, borough outline and three numbered references, with no recommendation shading. Closer zooms overzoom the same retained map pack.

Primary sources and licences

• Defra explanation of the 2022 noise maps
• Defra aircraft noise source
• Defra road noise source
• Defra railway noise source
• TfL Open Data
• TfL cycling-permission map
• Police.uk
• ONS small-area populations
• DfE school register
• Ofsted inspections
• OS Code-Point Open
• GLA boundary source
• OpenStreetMap contributors
• OpenFreeMap
• Open Government Licence v3.0
• Retained map style and font notices

Contains public sector information licensed under the Open Government Licence v3.0. Contains OS data © Crown copyright and database rights 2016 and Geomni UK Map data © and database rights 2019. ONS / OS © Crown copyright and database right 2026. Defra © 2023/2024; GLA / Ordnance Survey Open Data. Powered by TfL Open Data. Walking estimates are this app's calculations. Base map © OpenStreetMap contributors, OpenMapTiles and OpenFreeMap; Positron derives from CartoDB Basemaps, designed by Stamen and Paul Norman for CartoDB. See the retained notices for the full map/font terms.