What is Geodata?
Geodata is location information stored in a Geographic Information System (GIS).
By viewing data with a geographic component, we see it through a different lens.
Geodata tackles the problem about location because geographic problems require spatial thinking.
Let’s dive into the types, themes and sources of geodata.
Types of Geographic Data
As it turns out, there’s not one single type of geodata. Instead geodata exists in various forms. For example, we commonly use vector and raster to depict geodata.
1 Vector Files
Vector data consists of vertices and paths. The three basic types of vector data are points, lines and polygons (areas). Each point, line and polygon has a spatial reference frame such as latitude and longitude. First, vector points are simply XY coordinates. Secondly, vector lines connect each point or vertex with paths in a particular order. Finally, polygons join a set of vertices. But it encloses the first and last vertices creating a polygon area.
2 Raster Files
Raster data is made up of pixels or grid cells. Commonly, they are square and regularly-spaced. But rasters can be rectangular as well. Rasters associate values to each pixel. Continuous rasters have values that gradually change such as elevation or temperature. But discrete rasters set each pixel to a specific class. For example, we represent land cover classes to a set of values.
3 Geographic Database
The purpose of geographic databases is to house vectors and rasters. Databases store geographic data as a structured set of data/information. For example, Esri geodatabases, geopackages and SpatiaLite are the most common types of geographic databases. We use geographic databases because it’s a way to put all data in a single container. Within this container, we can build networks, create mosaics and do versioning.
4 Web Files
As the internet becomes the largest library in the world, geodata has adapted with its own types of storage and access. For example, GeoJSON, GeoRSS and web mapping services (WMS) were built specifically to serve and display geographic features over the internet. Additionally, online platforms such as Esri’s ArcGIS Online allow organizations to build data warehouses in the cloud.
Multi-temporal data attaches a time component to information. But multi-temporal geodata not only has a time component, but a geographic component as well. For example, weather and climate data tracks how temperature and meteorological information changes in time in a geographical context. Other examples of multi-temporal geodata are demographic trends, land use patterns and lightning strikes.
The truth is:
You can group geodata into as many themes as you want. They can be as broad or as narrow to your liking.
Here are examples of geographic themes:
- Administrative (Boundaries, cities and planning)
- Socioeconomic data (Demographics, economy and crime)
- Transportation (Roads, railways and airport)
- Environmental data (Agriculture, soils and climate)
- Hydrography data (Oceans, lakes and rivers)
- Elevation data (Terrain and relief)
Sources for Geodata
Are you trying to find open, authoritative geodata to use in your maps?
Before the concept of open data took off, organizations were protecting data as if it was Fort Knox. Since then, we are in a much better position.
Currently, there’s no single website that holds all the geodata in the world. Instead they branch out into what they are most specialized in.
For example, OpenStreetMap data is the largest crowd-sourced GIS database in the world providing countless applications for the public.
And finally, over 1000 satellites orbit the Earth collecting imagery of our planet. These 15 free satellite imagery sources give you the most up-to-date bird’s eye view of it all.