In brief:
- A geographic information system, or GIS, brings together hardware, software, data and methods to collect, store, analyse and map located information.
- It performs six functions: acquisition, storage, management, spatial analysis, cartographic representation and distribution.
- Solutions split between open source or proprietary software, and between local installation or hosted access, with no single formula standing out by default.
- Within a local authority, a GIS is not an end in itself: it works as a building block of the territorial information system, connected to the other data platforms.
A geographic information system designates the technical and organisational setup that collects, stores, analyses and represents information tied to a position in space. The acronym GIS circulates widely across local authorities, sometimes to name a specific piece of software, sometimes to name the whole function that runs from capturing a piece of data to distributing it as a map.
What is a geographic information system
A geographic information system brings together the means needed to process information that combines a location with descriptive attributes, what is known as geographic data. It is not limited to a mapping visualisation tool: it covers the entire chain, from capturing raw data to using it in an analysis or a decision.
What sets a GIS apart from a simple cartographic drawing tool is its ability to query and cross several layers of information with each other. Overlaying a zoning layer, a sewer network and a terrain elevation survey, then automatically querying the areas where these three layers overlap, is a geographic processing task, not a mere illustration.
The components of a geographic information system
A GIS works as a set where each component depends on the others. Removing just one is enough to make the rest unworkable.
Hardware and software
Hardware handles the computing and storage that processing requires, and its volume grows with the resolution of the geographic data being processed. Software, in turn, handles capture, analysis and representation: some tools are dedicated to geomatics, while others embed geographic functions inside a broader business tool, such as an asset or road management platform.
Data and methods
Geographic data is the raw material of the system. Its value depends directly on how well it is documented: the projection system, the update date and the precision level all condition the confidence one can place in it once it leaves the tool that produced it.
Methods govern the production, updating and quality control of this data, and the human organisation sustains those methods over time. A GIS without documented methods accumulates layers of data that, within a few years, nobody can say for certain which version is authoritative.
The functions of a geographic information system
Beyond its components, a GIS is defined by the functions it makes possible. Six functions come up systematically, even if their relative weight varies with the use case.
Acquisition covers manual capture, importing existing reference datasets and recovering field measurements. Storage organises this data in a structured database that can be queried and shared across departments. Management covers updating, consistency checks and the archiving of successive versions.
Then comes spatial analysis, which crosses several layers to answer a question, compute a distance, an area or a zone of influence, or identify overlapping objects. Cartographic representation turns this work into a map readable by a non specialist. Distribution, finally, shares the result with other internal departments, elected officials or, as part of open data, with the public.
The data a geographic information system draws on
A territorial GIS rarely relies solely on data produced entirely in house. It most often combines national geographic reference datasets, addressing, land parcels and administrative boundaries, with layers specific to the local authority: technical networks, regulatory zoning, built assets or street furniture.
This interplay between shared reference datasets and local data explains why the quality of a GIS is not measured only by the richness of its own layers, but also by its ability to stay synchronised with reference datasets that evolve independently of it. An addressing reference dataset updated by a third party and never reimported locally ends up desynchronising every process built on top of it.
The two main families of GIS solutions
Choosing a GIS solution does not come down to a brand or a vendor first, but to two structuring choices, independent of each other.
The first concerns the licensing model: an open source solution, whose source code is open and whose use depends on no vendor contract, stands against a proprietary solution, whose licence generally comes with contracted support. The second concerns the hosting model: installation on a workstation, which keeps full control over data and processing in house, stands against hosted access, where a provider runs the infrastructure and the updates.
These two choices combine freely: nothing prevents an open source solution hosted online, nor a proprietary solution installed locally. The deciding factor remains the volume of data to process, the in house skills available for maintenance and how closely the tool needs to integrate with the authority’s other systems, far more than a default preference for one model or the other. The same trade-off applies when choosing a local government data management solution.
GIS as a building block of the territorial information system
Taken in isolation, a geographic information system remains just another technical tool. It takes on a different weight once it is connected to the rest of a local authority’s information system, rather than kept as a specialised island that only a handful of staff know how to operate.
This requires, first, that the geographic data produced by the GIS remains usable outside it, in documented formats and shared reference datasets, the same condition already set for opening public data. It also requires the GIS to talk to the other building blocks of the information system: a territorial data platform that aggregates several sources, or tools that let staff visualise a territory’s data in a form readable by elected officials and non specialist staff.
This shared governance, more than the choice of software, conditions the real value of a GIS over time: a technically accomplished tool left isolated from the rest of the information system delivers less value than a more modest but properly interconnected solution.
Frequently asked questions
What are the components of a geographic information system?
There are usually five components that work together: the hardware that runs the processing, the software used to capture and analyse information, the geographic data itself, the methods that govern how it is produced and kept up to date, and the organisation that sustains those methods over time. Removing any one of them is enough to make the others unworkable.
What are the main functions of a geographic information system?
A GIS generally performs six functions: acquiring data, storing it in a structured database, managing and updating it, running spatial analysis that crosses several layers, producing cartographic output, and sharing it with other departments or the public. A given local authority does not necessarily use all of these functions with the same intensity.
Does exploiting a geographic information system always require the same type of software?
No. Solutions split between open source and proprietary software, and between installation on a workstation and a hosted online service. The choice mainly depends on the volume of data to process, the in house skills available and how closely the tool needs to integrate with the authority’s other systems, rather than on any one solution being universally superior.
What is a geographic information system used for in a local authority?
It is used to process a planning permit by crossing several zoning layers, to plan a technical network, to track the condition of a built asset, or to produce the maps that accompany a council decision. It also becomes the technical building block that feeds broader uses, from opening public data to the cross department steering of services.