Spatial data

Spatial data describe objects, areas, or phenomena that have spatial or geographical properties, such as position, size, or shape. Spatial data include information with geographical features, such as where a specific lake is located on Earth and how large and deep it is, or how many people live within a certain postal area code.

Geographic Information Systems (GIS) are a way to structure spatial data, linking geographic elements to attribute data. Geographic elements can be divided into vector elements (based on points, lines, or polygons) or raster elements (based on a grid).

Not all spatial data are GIS data. An Excel table with columns for postal codes and population is not GIS data but becomes GIS data if imported into a GIS program and linked to geographic elements that describe postal code boundaries or centroids. Conversely, data within Building Information Modeling (BIM), which describe buildings and infrastructure, is fundamentally spatial data but can also represent generic structures without a fixed geographical reference.

Below, we list several file formats, but many other formats may exist. Contact your local research data support service for advice on which file formats are appropriate for long-term preservation and sharing of the type of research data you are working with.

Raster and vector formats

More detailed information on raster and vector formats can be found on the Images page.

Raster data

GIS data in raster format are used to represent how a modeled or measured property (e.g., elevation, temperature, or vegetation fraction) varies geographically. An example of such raster data is the map used to show the spatial location of search results in the research data catalog here on Researchdata.se.

Vector data

GIS data used to create, for example, topographic maps, are typically stored in vector format. The number of columns in an attribute table may vary, and the information in the columns may differ.

Data management for GIS data

GIS data are often split into multiple files, each serving a different function, such as a file containing an attribute table, a file with the object’s geometry, a file with information about the coordinate system, and a file with metadata. Therefore, when moving GIS data from one folder to another, it is important to ensure that all files are included.

GIS data that underpin research results are often the result of a multi-step process, with operations that reduce and combine data from different datasets. For a secondary user to understand the dataset and how it was created, it is important that all steps in the processing chain are documented.

Geographic coordinate reference systems and map projections

A reference system is a systematic method for describing a location on Earth using coordinates. The World Geodetic System 1984 (WGS84)Opens in a new tab is a commonly used reference system for GIS datasets, used in, for example, the global positioning system (GPS).

For regional maps, a map projection is typically used to make distances, areas, and directions more uniform across a map. In Sweden, the projected coordinate reference system SWEREF 99 TMOpens in a new tab is used, where position is expressed in a northern direction (N) with seven digits and an eastern direction (E) with six digits (usually), both in metres.

The best way to describe the reference system and map projection used in a GIS dataset is to add an EPSG code from the EPSG Geodetic Parameter DatasetOpens in a new tab. This is supported by most GIS programs.

Access levels

GIS data that form the basis for GIS processing chains are often obtained from existing, and in many cases public, datasets. These do not need to be included in the dataset you share, but you must provide a clear source reference to the original datasets.

Certain GIS processing involves selecting and potentially modifying elements from existing GIS datasets. For example, a future city study may use existing urban GIS data for roads and parks. In such studies, some elements from the source datasets may be included in the final product. In this case, it is important to check the rights to distribute copies of the source dataset, such as its license. In Sweden, open data from Lantmäteriet are often used to create maps and figures, but in many cases, the source data cannot be openly shared again.

If GIS data contain protected data, accessibility may need to be restricted. GIS data that include personal information (e.g., location information for survey respondents) must be protected. Information relating to state security (e.g., infrastructure or military protected objects) is often protected by strong confidentiality, and even location information for certain endangered species’ habitats may need to be protected.

Recommended file formats for sharing and long-term preservation

There are many file formats used for GIS data. Open file formats are preferred for sharing, and a popular open format is GeoPackage, which packages both vector and raster data into one file. Common formats for simpler vector data include ESRI Shapefile, GeoJSON, and KML. For pure raster data, the open standard GeoTIFF is popular, but DEM and ESRI Grid are also common. MapInfo Interchange Format is a proprietary format but has broad support and is easy to reuse for further research.

Recommended file formats for sharing

• OGC GeoPackage (.gpkg)
• ESRI Shapefile (.shp)
• GeoJSON (.geojson)
• Keyhole Markup Language (.kml)
• GeoTIFF (.tif, .tiff)
• ESRI GRID (.adf, .asc, .grd)
• Digital Elevation Model (DEM) Format (.dem)
• Geographic Markup Language (.gml)
• NetCDF (.nc)
• MapInfo (.tab, .dat)
• MapInfo Interchange Format (.mif, .mid)
• CSV (.csv)

Recommended file formats for long-term preservation in archives or similar

• OGC GeoPackage (.gpkg)
• ESRI Shapefile (.shp)
• GeoJSON (.geojson)
• Keyhole Markup Language (.kml)
• GeoTIFF (.tif, .tiff)
• Digital Elevation Model (DEM) Format (.dem)
• NetCDF (.nc)
• CSV (.csv)