Glossary
The terms we use when we talk about spatial analysis, accessibility and planning — defined plainly, one page each.
38 terms
15-minute city
A planning idea in which residents can reach everyday needs, such as shops, schools, healthcare and work, within a fifteen minute walk or cycle from home.
Two-Step Floating Catchment Area (2SFCA)
An accessibility method that compares supply and demand in two steps, so a facility serving thousands counts differently from one serving dozens.
Accessibility
How easily people can reach the things they need from where they are. First defined in 1959 as the potential of opportunities for interaction.
Accessibility analysis
Measuring how easily people can reach the places they need, such as schools, jobs, healthcare and green space, from where they live.
Active mobility
Getting around under your own power, mainly walking and cycling, including pedelecs, wheelchairs and scooters.
Area of interest (AOI)
The geographic area an analysis covers, defined by a boundary, everything outside which is excluded from the result.
Catchment area
The area that can be reached from a point within a given travel time or distance, following the real network rather than a straight line.
Choropleth map
A map that shades areas by the value of a statistic, so darker or stronger colours mean higher values. Used for rates and densities across regions or districts.
Climate adaptation indicators
Measures that describe how exposed a place is to heat, heavy rain or drought, and how well it can cope, at a scale planning can act on.
Connectivity
How well the paths in a network connect to each other. Higher path and intersection density means higher connectivity, and shorter real journeys.
Deficit area
An area formally identified as falling short on a defined standard, such as green space or cooling, which makes it a place planning can act on.
Geocoding
Turning addresses or place names into coordinates so they can be mapped and analysed. The reverse turns coordinates back into an address.
Geospatial data
Any data that includes a location, whether as coordinates, an address or an area, so it can be placed on a map and analysed spatially.
GIS
A system for storing, analysing and mapping data that has a location attached, so you can ask where something happens and not only how much of it there is.
Gravity model
An accessibility method where every destination contributes, but nearer ones count more, with the fall-off set by a distance decay parameter.
H3 grid
A system that divides the earth's surface into hexagonal cells at several resolutions, used to compute and display values over an area.
Heatmap
A map that shows a computed value across a continuous surface using colour, rather than symbols at individual locations.
Huff model
A method that estimates the probability of someone choosing one location over its competitors, based on how attractive each is and how far away.
Indicator
A defined, repeatable measure of something, used to assess a situation, compare places, or track progress towards a goal.
Isochrone
A line joining all the points reachable in the same travel time from a starting point. The travel time version of a contour line.
Land use
What an area of land is actually used for, such as housing, industry, farmland or recreation. The basis of most planning regulation.
Local accessibility
Accessibility at neighbourhood scale, over short distances and mostly on foot or by bike, rather than across a whole city or region.
Location intelligence
Using the location dimension of business or planning data to make decisions: where to put something, who it reaches, and what is nearby.
Mobility concept
A plan for how people will reach and move around a development or district, used to justify fewer parking spaces by providing alternatives.
On-demand transport
Public transport without a fixed route or timetable. Vehicles are booked and routed according to the requests that come in.
Open source GIS
GIS software whose source code is publicly available and free to use, modify and run, such as QGIS, PostGIS and GOAT.
Planning support system (PSS)
A digital tool that supports planning decisions by combining data and models, so different scenarios can be tested before anything is built.
Point of Interest (POI)
A specific location that matters in an analysis. In accessibility work, usually a place of everyday need: a supermarket, a school, a doctor, a pharmacy.
Public transport quality classes
A standardised rating of how well a location is served by public transport, combining how close the stops are with how often services run.
Raster data
Spatial data stored as a grid of cells, each holding a value. Suited to continuous things like temperature, elevation or land cover.
Routing
Calculating the best path between places across a transport network, and the time or distance that path takes.
Service gaps
Areas or times where people cannot reasonably reach what they need, because the service is absent, too far, or runs too rarely.
Site selection
Choosing where to locate something by comparing candidate places against the criteria that matter, such as who they reach and what is already nearby.
Soil sealing
Covering ground with impermeable material, so water cannot infiltrate. A core indicator for heat and heavy rain risk.
Spatial analysis
The set of methods that use location to find patterns in data: what is clustered, what is near what, what is reachable and what is not.
Travel time
How long a journey between two places actually takes by a given mode, measured along the network rather than as straight line distance.
Urban planning
The practice of shaping how land is used and how people move in cities and regions, through plans, regulation and public investment.
WebGIS
A GIS that runs in the browser, so spatial data can be analysed, mapped and shared without installing desktop software.