A technique for mapping of areas using photographs taken directly from above. Though used mainly in map-making, it can also be used for the planning of archaeological sites. For large-scale map-making the photographs are taken from the air, a sequence along each flight path with each exposure overlapping the next by 60%. Adjustment is made so that the photographs can be laid side by side in a mosaic, with common reference points lying over each other. They are then converted into maps by the use of multiple projectors. A similar technique can be used to plan smaller-scale features such as excavations. The camera can be mounted on a rigid frame, and moved along so that it takes overlapping vertical photographs. It can greatly speed up the mapping of complicated features. Many of today's maps are largely produced by this method.