In: Wagner W., Szekely, B. (eds.): ISPRS TC VII Symposium - 100 Years ISPRS, Vienna, Austria, July 5-7, 2010, IAPRS, Vol. XXXVIII, Part 7B 
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use of it may not have access to the hardware, software and 
expertise required to manipulate the data to best effect. The new 
English Heritage Guidance paper aims to advise people as to 
how they can get the most out of lidar data in a normal working 
environment using everyday technology. The most obvious 
example of this is simply using paper print outs in the field, an 
application that can be used either by professional analytical 
field surveyors looking for additional data sources, or by 
amateur archaeologists undertaking local research or walk 
through surveys. As noted above, one of the most common 
ways in which lidar data is used is as a hillshaded image and 
this is the simplest way to work with a printed image. The 
advantage that lidar has over a conventional aerial photograph 
is that it is possible to control the direction of the lighting and 
thereby light from angles impossible in the natural world so as 
to reveal otherwise hidden features. Unfortunately the simplest 
hillshaded image to produce, that lit from a single direction, has 
the possibility of missing any features that are aligned on the 
direction of the light source as shown in figs 5 -6. 
Figure 5 - Ridge and furrow near Alchester 
illuminated E-W (lidar © Cambridge University 
ULM (Dec 2005)). 
Figure 6 - Ridge and furrow near Alchester 
illuminated N-S (lidar © Cambridge University ULM 
(Dec 2005)). 
In order to get around this for hardcopy imagery it is necessary 
to produce composite images. This can be done by creating 
composite images using the transparency tools within image 
editing or GIS packages, but a more effective process is now 
seen in the use of principal component analysis (PCA) a 
statistical method to examine multiple hill-shaded images and 
compile a composite image that shows the main features from 
each image (Devereux et al 2008). One negative element of 
this, however, is that the false colours and the multiple 
combined lighting angles mean it can be difficult to 
differentiate between cut and built features as shadow and 
highlights can be present for both. 
4.4 Interactive mapping 
Whilst high quality “flat” images using hill-shading or PCA 
techniques can provide a relatively user friendly way of 
working with lidar, they do not fully capitalize on the 
interpretative potential of the lidar data. For the professional 
user there are great benefits from working with lidar data 
interactively, by manipulating the data as part of the 
interpretative process, so as to highlight specific features and 
understand as much as possible about their form and extent. 
Key to the necessary workflow is the ability to view and 
manipulate the data in 3D (although currently this is strictly 
only 2'AD within affordable software) something has been made 
possible by combining viewing and mapping software. English 
Heritage has developed over time working practices for 
archaeological interpretation and mapping from aerial 
photographs, and these have now been greatly enhanced by the 
integration of the use of lidar data. 
Figure 7 - Interactive use of lidar data in viewing and 
mapping software 
5. CONCLUSION 
Lidar data can be an immensely useful tool for archaeologists 
and has unrivalled capabilities for mapping in certain 
environments, such as within particular types of woodland. 
There are, however, still lots of uncertainties within the broader 
archaeological community about just what it can and cannot do. 
There are also many aspects of the data collection that need to 
be clearly understood and correctly specified if the data 
provided is to be as useful as possible. To this end the English 
Heritage guidelines will hopefully help those intending to use 
lidar for archaeological survey to avoid some of the pitfalls and 
maximize the value for money of this new technique. The 
guidelines are available as a downloadable PDF through the 
English Heritage website http://www.english- 
heritage.org.uk/publications/light-fantastic/ and there is further 
information available on the Aerial Survey & Investigation web 
pages http://www.english-heritage.org.uk/aerialsurvev.