Raster vs vector data

Discover the differences between raster and vector data and its uses

Shapes and locations of features on maps need to be described in numbers, so the information can be read by computers.

Computers store information in sequences of binary digits (bits), which form a code for every possible number or letter. Coincidentally, maps reference geographical locations on the Earth's surface through a system of coordinates. These coordinate systems can be local, national, or international. Look at Ordnance Survey (OS) paper maps and you will notice, along the sides, there are a series of numbers associated with a grid covering the whole map area.

These numbers refer to coordinates from the British National Grid. All locations and shapes can be defined in terms of x and y coordinates from a given grid system. These numerical values can be used to translate map information into digital form, in both vector and raster formats.

What is raster data?

Raster data is like a digital photograph. 

The entire area of the map is subdivided into a grid of tiny cells, or pixels. A value is stored in each of these cells to represent the nature of whatever is present at the corresponding location on the ground.

The main use of raster data involves storing map information as digital images, in which the cell values relate to the pixel colours of the image. To reproduce the image, the computer reads each of these cell values one by one and applies them to the pixels on the screen.

What is vector data?

Vector data is like a list of values.

The features are recorded one by one, with shape being defined by the numerical values of the pairs of xy coordinates, so that:

  • A point is defined by a single pair of coordinate values.
  • A line is defined by a sequence of coordinate pairs defining the points through which the line is drawn.
  • An area is defined in a similar way, only with the first and last points joined to make a complete enclosure.

The position and shape of a building is captured as a series of four pairs of numerical coordinates. To reproduce the building in a GIS, the computer reads these values and draws a line linking the coordinate positions.

The vector version can also store additional context information about these features – the attributes – a very important aspect.

Raster vs vector

Both types of data are useful, but there are important differences between raster and vector data.  

07_Raster vs Vector_smallscale

Raster data

  • Relatively high data volume

  • Slower display

  • Has no attribute information

  • More pleasing to the eye

  • Inherently stores how features should look in the GIS

07b_Raster vs Vector_largescale

Vector data

  • Relatively low data volume

  • Faster display

  • Can also store attributes

  • Less pleasing to the eye

  • Does not dictate how features should look in the GIS

Related information

  • GIS software

    In this guide to choosing GIS software, Ordnance Survey have shared a list of recommended GIS mapping software solutions.

  • Uses of GIS

    Explore the potential of GIS with real-world examples, from GIS in healthcare and emergency services, to local government and utilities.

  • GIS data

    Access accurate geospatial data through data products by Ordnance Survey, a major GIS data provider for Great Britain.