Geographic data: formats and types

In short:

1. Geographic data always combines a position in space with information that describes it, and that combination is what sets it apart from plain tabular data.
2. It comes in two main formats, vector or raster, each suited to a different type of object.
3. National geographic reference datasets (addressing, land parcels, administrative boundaries) provide a common foundation for most territorial uses.
4. Once structured, this data feeds both public data releases and a local government’s internal management tools.

Geographic data refers to any information that describes an object or phenomenon located within a territory, whether a land parcel, a network, a facility or a regulated zone. It always combines a position in space with attributes that specify its nature, which sets it apart from plain tabular data with no spatial anchor.

What is geographic data

Geographic data brings together three components that work as a whole. The spatial position places the object within a coordinate system, usually tied to a national projection. The attribute information describes the object itself: its nature, its name, its physical or regulatory characteristics. Metadata completes the set by specifying the source, the update date and the precision level of the data.

This three-layer structure explains why a plain address or street name is not enough to qualify as geographic data in the strict sense: the position and the attribute must be linked within the same record, usable by software without re-entry.

The two main formats: vector and raster data

The choice of format depends mainly on the nature of the object represented, not on a technical preference.

Vector mode

Vector mode represents objects as points, lines or polygons defined by their coordinates. It suits objects with clear boundaries: a land parcel, a road segment or the perimeter of a regulated zone naturally lend themselves to this representation, which keeps its precision at any zoom level.

Raster mode

Raster mode divides space into a grid of cells, each carrying a value. It suits continuous phenomena rather than delineated objects: an aerial image, a terrain elevation model or a ground temperature reading are naturally expressed this way. Its precision depends directly on cell size, and therefore on the resolution chosen at acquisition.

The geographic reference datasets that structure public data

Rather than recreating its own reference points, each data producer relies on a small number of shared reference datasets that act as a common foundation.

Addressing and land parcels

A national addressing reference dataset links each address to a precise position, which allows a report or request to be located automatically without manual re-entry. A land parcel reference dataset does the same for property ownership, used both for reviewing planning permits and for local taxation.

Administrative boundaries

An administrative boundaries reference dataset divides the territory into municipalities, inter-municipal bodies, departments and regions. It frames nearly all territorial processing, from a simple population count to cross-referencing several data layers.

Geographic data in the opening of public data

Geographic data makes up a significant share of the datasets covered by local governments’ open data releases: plans, networks, regulatory zoning and public facilities all feature systematically, subject to the exceptions that protect the safety of people or sensitive facilities.

This release adds a constraint beyond a strictly internal use: the format must remain readable by third-party tools, and the documentation must spell out the projection system and update date, without which the data loses much of its value once it leaves the software that produced it.

Territorial uses of geographic data

Within a local government, geographic data feeds very different uses depending on the department mobilising it. A geographic information system gathers and cross-references it to produce analyses, whether reviewing a planning permit or planning a technical network.

It also feeds the tools that visualise a territory’s data in a form accessible to elected officials and non-specialist staff, as well as the broader building blocks of a territorial data platform that aggregates these layers with other sources. When these flows feed a real-time management console, they join the logic of an urban hypervision system, which overlays several layers into a single view.

Frequently asked questions