ABSTRACT
The main focus of this book is on the acquisition of spatial information by means of survey in the field. Ways have been described in which individual surveys can be placed within the framework of a wider co-ordinate system to enable others to locate the site, and to make it possible to combine the data from a number of surveys carried out by different people or at different times. Often, it would be desirable to overlay the survey data onto a base of contemporary mapped data, and this is also possible provided the co-ordinate system used for the survey is the same as that used for other mapping. What is often a problem is the provision of the ‘other’ data. In many countries digital map data are unobtainable as a product of a national mapping agency, sometimes for political or security reasons. In others, such as the UK, the data are readily available from the Ordnance Survey, but at a price which is likely to be daunting to the individual or, say, an amateur group (at least for the larger-scale data sets). Those working in the United States are in a much more favourable position, as large quantities of data produced by the United States Geological Survey (USGS) can be downloaded from web sites free of charge, while others come on CD at a quite modest cost. (A more detailed description is given in the case study of a site in New Mexico.) Workers elsewhere who need extensive coverage of large-scale data have no choice but to pay for it, either in time or money, but smaller-scale data can be of use in showing the locations of sites or in producing wide-scale distribution maps, and there are some sources of data of this type which are available to anyone at no cost.
