Raster Images are commonplace in archaeological archives and, while they can be the product or component of a number of different processes, they essentially consist of the same basic elements i.e. an image composed of a matrix of pixels with a fixed size/resolution. In archaeology, raster images can be created from a wide variety of processes ranging from original data capture such as digital photographs, scans and drawings through to outputs or ‘products’ such as plotted geophysical survey data and images from GIS layouts.

This guide aims to cover the common types of raster image created as components of archaeological research, these include:

• Digital photographs
• Aerial photographs
• Document scans
• Screenshots and output from vector applications
• Original images such as illustrations, posters, etc.

Although some technical description will be given in this guide, in depth discussion of aspects of raster images such as resolution, colour space and bit depth won’t be covered and are more than adequately explained in existing guides, specifically JISC Digital Media’s ‘Advice on Still Images’ and in the AHDS Bitmap (raster) Image Preservation Handbook. Likewise, vector images are covered in more detail in the Vector Images guide. For both raster and vector images, as common components of larger project workflows, links are also made to technique focused guides such as CAD, GIS and Virtual Reality.