Geospatial Concepts

An introduction to geospatial concepts

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"Everything is related to everything else, but near things are more related than distant things"
- Waldo Tobler, First Law of Geography

What is GIS?

GIS stands for Geographic Information Systems. But what exactly does that mean? 

A common misconception is that GIS is synonymous with 'mapping', or making maps. This is, at best, an incomplete understanding of the term. 

As a concept, GIS is the linkage of spatial information (where things are) with description information (what things are). It is a way to represent objects and conditions in the real world, such as the location of fire hydrants or rainfall precipitation over time in a given area. 

As an application, GIS is a computer system that:

  • captures;
  • stores;
  • manipulates;
  • analyzes;
  • manages;
  • and presents geospatial data.

What is Geospatial Data?

Geospatial data are data with a spatial component. This means the data references a unique location. Much of the data we work with today contains some sort of spatial reference. Geospatial data includes GPS data, LiDAR data, satellite and aerial imagery, as well as data corresponding to a particular address or set of coordinates.

A GIS can help you store, manage, analyze and share geospatial data.

Geospatial data is typically split into two general categories:

Vector data
Vector is commonly used to represent objects in space. It is organized in a tabular structure that allows one to assign attributes to each feature. Vector data is composed of discrete geometric locations known as vertices that determine its shape: points, lines, or polygons:
  • Points are described by its X, Y coordinates (and optionally, Z coordinate). Examples of objects often represented as points include trees, fire hydrants and businesses.
  • Polylines are created by two or more connected vertices that do not form an enclosed shape. Examples of objects often represented as polylines roads, rivers, and trails.
  • Polygons are a series of connected vertices that do form an enclosed shape. Examples of objects often represented as polygons include building footprints, property parcels, and administrative boundaries such as state and county boundaries.
Raster data
Raster data is made up of a grid or matrix of cells. Each cell contains a numeric value representing the conditions for the area covered by the cell. Raster data includes images and scanned maps, as well as data depicting continuous qualities of space (as opposed to discrete physical objects in space), such as elevation, temperature, and distance.