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type of survey addressed in the current metric survey 
specification. Discussion and examples of TLS are therefore 
limited to this class of system. 
1.2 Project design 
The project described in this paper has been funded through 
the English Heritage Archaeology Commission’s budget. It 
aims to produce an addendum to the existing metric survey 
specification, thus allowing laser scanning to be considered 
alongside existing techniques within the survey of the 400 
monuments directly under the care of English Heritage and 
many of England’s 450,000 listed buildings. It is, however, 
important to understand that the inclusion of TLS in the 
specification does not instantly deem it suitable for the 
replacement of other survey techniques. It is normal that 
before any survey work is undertaken a project brief is 
defined. This should describe the variable elements of a 
particular survey and hence it is the responsibility of this 
document to define the appropriate technique/s. The 
specification document produced from this project is simply 
intended to define the level to which TLS, if appropriate for 
use, should be applied. The document is also intended as a 
guide for users. It is not intended to stifle the development of 
TLS by imposing unrealistic or unnecessary constraints on 
the application of laser scanning systems. In fact the project 
explicitly aims to steer the development of laser scanning so 
that it meets the needs of cultural heritage users, 
archaeologists, architects and building historians. 
An iterative process of specification, survey, consultation 
and revision was used to define the specification. Based on 
previous experience an outline project brief was agreed to 
allow an initial data collection phase to take place. After 
analysis of this data, a steering committee comprising nine 
individuals (including the authors), was consulted. The 
members of this committee were selected to represent both 
the client and contractor. Contractors were selected from the 
survey community, including those already offering 
commercial photogrammetric or TLS services. End users 
were represented by members of English Heritage, including 
some from their Centre for Archaeology. After this review a 
second survey was performed before the initial document 
was again revised. This draft specification (English 
Heritage, 2003) was then released for comment to the wider 
UK survey community before a final survey to confirm the 
suitability of the document (at the time of writing these two 
stages are yet to be completed). This extensive process of 
consultation will ensure the practicality, impartiality, 
relevance and ultimate value of the final document. 
2. OVERVIEW 
From the outset it was clear that the specification could be 
divided into three interrelated segments. These three 
segments represent the clear logical progression of laser 
scanning (or indeed any other survey technique): data 
capture, data use and data storage (or archiving). Although 
each segment depends on another, for example the methods 
employed for data collection will implicitly depend upon the 
intended use of data, using these three broad categories 
allowed a structured approach to the project. 
2.1 Data capture 
The capture of data clearly depends on the scanning system 
in use as this will dictate the workflow and techniques 
applied. This includes issues such as methods for 
registration, available/required field of views, the density of 
data capture and the requirements for any additional 
information. 
2.2 Data use 
Although scanning has been used for architectural survey for 
over three years, standard products have yet to be defined. 
The use of TLS data was therefore not specifically addressed 
by the document with the main emphasis placed on the 
collection and storage of point cloud data. However, in order 
to make the specification sensitive to the needs of possible 
end products the following were defined as potential outputs 
although no specification of how they should be presented, or 
to what level they should attain, was provided. 
■ CAD models (by primitive modelling) 
■ Meshed models 
■ Profiles and cross sections 
■ Animations 
Work is still required to educate clients who commission 
TLS that the production of traditional products (such as line 
drawings) from scan data may not be the most appropriate 
way of applying laser scanning. 
2.3 Data storage 
All survey data generated for English Heritage is ultimately 
deposited in the National Monuments Record, Swindon, UK. 
The storage of data is therefore a vital part of the 
specification process. Access to the data must be possible 
despite the possibility of a number of years passing between 
data collection and processing. The biggest obstacle to this 
is the current lack of a standard data format. A standard 
format for TLS would allow for the efficient transfer of data, 
improving software development and ensuring the continued 
use of TLS as a technique to supply archive data. Any 
standard data format also requires appropriate metadata to 
allow for long term data storage and management. 
3. FIELDWORK 
Two separate surveys were performed at Tynemouth Priory, 
Newcastle upon Tyne in February and May 2003. A further 
survey is planned for Clifford’s Tower, York although at the 
time of writing the details have yet to be confirmed. 
Tynemouth Priory has been used on several previous 
research projects looking at the application of metric survey 
techniques (Mills et ah, 2000, Barber et al., 2002), in 
addition to being the subject of several phases of survey by 
English Heritage. As it provides a clear, open and local site 
it was an ideal location for the first two surveys of the 
project. Both surveys concentrated on the remains of the 
priory church (Figure 1), a ruin approximately 92 m x 21 m 
in size with the tallest structure reaching 22 m in height. 
During the first visit a substantial survey was performed