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TOWARDS A STANDARD SPECIFICATION FOR TERRESTRIAL LASER SCANNING
OF CULTURAL HERITAGE
David Barber 1 , Jon Mills 1 and Paul Bryan 2
1. School of Civil Engineering and Geosciences, University of Newcastle upon Tyne, Newcastle upon Tyne
2. English Heritage Metric Survey Team, English Heritage, York
KEYWORDS: Cultural Heritage, Specification, Terrestrial laser scanning, Standards, Guidelines, Architectural Heritage
Conservation, Archaeological Heritage Conservation, Close Range Photogrammetry and 3D Scanning.
ABSTRACT:
The use of terrestrial laser scanning for cultural heritage recording is becoming increasingly popular. Although in some cases laser
scanning has been met with a degree of scepticism, scanning has, on the whole, been received with a great deal of enthusiasm. This
zeal has ensured laser scanning is now at the forefront of many new projects for the documentation of cultural heritage, leading to
the need to standardise the outcome of laser scanning surveys to ensure data is collected in a manner that can produce products
useful to the end user. The current Metric Survey Specification for English Heritage, the body responsible for preserving and
enhancing England’s cultural heritage, contains similar requirements for photogrammetric, non-photogrammetric and topographic
survey. This project increases the scope of the specification by introducing terrestrial laser scanning into the surveying workflow. It
informs about the advantages and disadvantages of using laser scanning, highlighting the pitfalls of the technique and producing
sample datasets that show exemplary practice of laser scanning within the field of cultural heritage recording. Guidelines, for the
application of terrestrial laser scanning to cultural heritage, have been formed based on the work.
A number of issues surround the definition of such a specification, such as broad range of scales at which laser scanning can be
applied, and the black box nature of some of the instruments. In particular this project deals with objects at the “building scale”
range, typically surveyed using photogrammetry or rectified photography. The guidelines have been formulated based on three laser
scanning surveys, at different English Heritage sites. In order to remove any bias for a particular instrument it was important that
different laser scanning systems were considered. After the completion of each survey the draft document was examined and
updated. As it is essential that a specification is also a practical guide to implement outside of test projects it was important that the
end users of the specification were properly consulted throughout the process. Therefore, a steering committee, whose members
represented a cross section of laser scanning practitioners, surveyors and experts in the field of cultural heritage recording in the UK,
was formed to provide guidance during the project. The project does not claim to produce the definitive specification for terrestrial
laser scanning in cultural heritage as the subject is particularly complex, however it does provide a useful starting point for future
discussion and revision. Although the definition of a specification could smother the development of terrestrial laser scanning, this
project aims to guide the development of scanning to meet the needs of the end users (archaeologists, architects, building historians
amongst others).
1. INTRODUCTION
1.1 The role of a specification
English Heritage, the national body for the protection and
conservation of England’s historic environment, has
maintained a standard specification, covering all existing
types of metric survey for over 5 years. The current Metric
Survey Specification for English Heritage (Bryan and Blake,
2001) outlines the current requirements for survey by
rectified photography, photogrammetric, orthophotographic,
architectural and topographic techniques. These techniques
play a key role in the understanding of a heritage site
(Clarke, 2001) and the specification ensures that, when
required, a repeatable level of geometric precision and
narrative recording is achieved. Within English Heritage 82
survey projects have been completed to the defined level to
date.
A survey specification is intended to define the standards to
which work must be completed. It covers issues ranging
from the required geometric accuracy of data to the required
format, along with all of the contractual responsibilities of
those involved. It ensures that the contractor understands
what is required and serves to manage a client’s expectations.
A specification also ensures standardisation between
projects, a vital requirement for organisations such as English
Heritage who both commission and advise upon a large
number of projects each year and who have a commitment to
the tax payer to achieve the best possible value.
The current metric survey specification does not, however,
include terrestrial laser scanning (TLS). TLS is an
increasingly popular survey technique which has been met
with great enthusiasm by many users. There is, however, a
need to standardise the technique’s processes and
deliverables to ensure laser scanning provides the repeatable
level of recording that photogrammetry for example
currently provides.
Defining a specification for TLS data is complicated by the
wide variety of systems and workflows available. TLS can
be arranged into two broad groups: the first being close range
scanning, operating at ranges of less than two meters and
therefore mainly restricted to small objects and artefacts; the
second including scanners that operate to ranges of greater
than two meters allowing for the efficient survey of building
façades and monuments. It is this second group of scanners
that most closely resembles instrumentation suitable for the
