CIP A 2003 XIX th International Symposium, 30 September - 04 October, 2003, Antalya, Turkey 
■ Scanning artefacts - These are the result of 
selections made during the scanning process. For 
example, by choosing to use a higher point density 
in the horizontal axis than in the vertical axis a 
point cloud can wrongly emphasise vertical linear 
features. A second artefact is the cropping of a 
scan scene so that important parts of the 
subject/scene are not visible. This may be a 
particular problem with tall buildings. In worst 
cases a viewer looking at only the point cloud 
could misinterpret such cropping as actual 
geometric features, Figure 4 shows an example of 
the problem. 
Figure 4 Example of cropping a scan scene 
5. SUMMARY AND CONCLUSIONS 
The definition of a specification for the collection of point 
clouds using TLS is a major step in the adoption of laser 
scanning as a standard survey technique for cultural heritage. 
The use of a standard specification has advantages for both 
client and contractor in addition to focusing the needs of a 
particular technology. 
The specification has been divided into three segments: data 
capture, data use and data storage; however each segment is 
clearly interrelated and has been considered in relation to 
each other. Standard point densities have been defined in 
addition to the required accuracy for point measurements. 
Definitions for terms used in scanning surveys have also 
been outlined. 
A major theme of the discussion has been ensuring the 
impartiality of the document from any one particular 
scanning system. Three different systems, each representing 
a particular type of laser scanner, were used. The use of 
multiple systems ensured the workflows employed by each 
were considered. A notable difference was seen between 
systems that used a known station location and those that 
relied on a resection calculation. 
The specification defined as a result of this project does not 
claim to be the definitive standard but does provide a basis 
for future discussion and revision. The paper presented here 
has provided an outline of the issues covered by the 
specification, illustrated with examples of some of the 
problems faced. As the technology continues to develop it is 
anticipated that the specification will evolve. The results 
reported in this paper represent the initial experiences of the 
project. Readers are recommended to consult the final 
addendum once the project has been completed. This will 
report the requirements of the specification in full. 
6. REFERENCES 
ANSI, 2000. Safe Use of Lasers (Pub 106) American 
National Standards Institute Z136.1. 
Barber D. M., Mills, J. P. and Bryan, P. G., 2002. 
Experiences of laser scanning for close range structural 
recording. Proceedings, International Workshop on Scanning 
for Cultural Heritage Recording, Corfu, Greece. 160 pages: 
121-126. 
Boehler, M. and Marbs, A., 2002. 3D scanning instruments. 
Proceedings, International Workshop on Scanning for 
Cultural Heritage Recording, Corfu, Greece. 160 pages: 9- 
12. 
Bryan, P. G. and Blake, B., 2000. Metric survey 
specification for English Heritage. English Heritage, 
Swindon. 111 pages. 
BS, 2001. Safety of Laser Products Part 1 Equipment 
classification. Edition 1.2. British Standard, BS EN 60825-1. 
Clark, K., 2001. Informed conservation - understanding 
historic buildings and their landscapes for conservation. 
English Heritage. 123 pages. 
English Heritage, 2003. An addendum to the metric survey 
specification for English Heritage - Draft June 2003- 
Terrestrial laser scanning. (Unpublished) 18 pages. 
HADCOCK, R. N., 1991. Tynemouth Priory and Castle. Fourth 
Edition, English Heritage, London. 32 pages. 
Mills, J. P., Peirson, G. C., Newton, I. and Bryan, P. G., 
2000. Photogrammetric investigation into the suitability of 
desktop image measurement software for architectural 
recording. International Archives of Photogrammetry and 
Remote Sensing, 33(B5): 525-532. 
IEC, 2001. Safety of laser products - Part I: Equipment 
classification, requirements and users guide. Edition 1.2. 
International Standard, IEC 60825-1. 
LAS Specification., 2002. LAS Format Definition. 
http://www.ziimaging.com/lasformat/_notes/LAS_format.pdf 
Last accessed June 2003. 
7. ACKNOWLEDGMENTS 
The authors wish to thank Clive Boardman, Bill Blake, Tom 
Cromwell, Tony Davies Graham Hunter, Faraz Ravi and 
Tony Rodgers, in addition to acknowledging the assistance of 
Leica Geosystems, Z+F-UK and Riegl UK. The authors also 
wish to thanks the project sponsors the English Heritage 
Archaeology Commissions Team (Project No. 3378).