Page 143 - Green - Maritime Archaeology: A Technical Handbook. 2nd ed

122 Maritime Archaeology: A Technical Handbook, Second Edition
measurements made on the Mary Rose remain unprocessed and the final report has yet to be published. The DSM program was later rewritten as Web for Windows (a somewhat confusing term nowadays as Rule’s coining of the word “web” pretty much predated the term now widely understood to be the Web as in the World Wide Web).
D. SITE SURVEYOR 1. Introduction
After the initial development of Web, there were not any major updates of the program until the mid-1990s and a huge number of copies exist (prob- ably pirated versions). A more sophisticated program called Site Surveyor was developed in the late 1990s by Peter Holt of 3H Consulting Ltd (Holt, 2003). Much of the following section is based on the Site Surveyor instruc- tion manual and the author is grateful to Peter Holt for allowing its repro- duction here. This program, which is dongle protected, is based on far more rigorous algorithms than Web and has a much more sophisticated interface.
2. Control Points
One of the rules of this survey philosophy is that the network of control points should be separated from the network of artifact points. The control network is a network of fixed survey control points placed in and around the site that are not used to directly position artifacts or structure. The site should be covered by the simplest network positioned using high-quality measurements. It is important to note that these control points must remain even if the site was excavated and recovered. The relative positions of the framework of control points are first determined in order to serve as a base for the detail survey. One major advantage of separating the roles of the control points is that the process of positioning the artifacts becomes easier. The control points and the artifact points are sometimes referred to as datum points in some marine archaeological literature, usually when no dis- tinction is made between the two types of points.
A number of basic principles apply to the survey when using Site Sur- veyor. A circular or elliptical network of control points should surround the whole site and at least four distance or baseline measurements should be made to each point. The maximum distance between control points should be no more than 15 m, measurements between control points should form a set of braced quadrilaterals and, where possible, the same measurements should be repeated a number of times. Depth measurements should be