Vector images: A guide to good practice

Images appear in many contexts and may be used for different purposes. An image is usually a two-dimensional representation of something and may form the empirical data material in a context or be used as an educational and visual aid for example. There are two main image file formats used to describe digital images. These are usually referred to as vector images or raster images (these are sometimes also referred to as bitmaps). Both image file formats have their advantages and disadvantages. For example, the vector format handles enlargement better than the raster format  but is not able to represent colour nuances as accurately. Vector images are commonly used in GIS and CAD, for example, while digital photographs are the most common type of raster image. This guide aims to provide guidance on what to consider when preserving two-dimensional vector images. For guidance on handling raster images, see our guide in the same series: Raster images: a guide to good practice. 

The guide covers the most common file formats used for storing vector images and which formats are suitable for archiving. It will also discuss the archival strategies that may be used to ensure that the quality of the files is maintained. Although some basic technical descriptions will be given in the guide, it is not intended to provide a more in-depth account of the technical specifications of vector images. Three-dimensional vector objects are often part of complex 3D datasets, are stored in different formats from 2D data and will not be covered in this guide. Although vector graphics are common in GIS and CAD, for example, this guide does not focus specifically on the management of GIS or CAD datasets.