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• automated orientation/triangulation of model/s 
• multiple viewing of 3D model/s 
• plotting of linework - even though analytical plotters are still the preferred choice for this, due principally to the strain on an 
operator continuously viewing a 3D digital image on a computer screen, there is still huge potential here for the automation 
of line/feature extraction drawing 
• manual generation of digital elevation model (DEM)/digital terrain model (DTM) 
• automatic generation of digital elevation model (DEM)/digital terrain model (DTM) 
• generation of digital orthophotograph 
• generation of montages 
• perspective scenes, walk throughs and fly throughs 
Within our own heritage application we have noted that some features have more immediate use than others whilst some, such as the 
automated DEM/DTM generation, are not and probably never will be, ‘100% fool-proof in terms of accuracy of 3D data generated. 
Therefore we firmly believe care must still be exercised when applying some of these automated features in close range projects. 
Within the work of English Heritage close range photogrammetry has subsequently been used on numerous projects relating to the 
conservation and preservation of the historic environment. This has included many of its own 409 historic monuments and as well as some 
of the thousands of privately owned ancient monuments and listed buildings landscapes located throughout England. Even though the 
usage of some of the more ‘traditional’ products, such as line drawings, has declined in recent years the technique is still being used not 
only for recording purposes but other associated activities such as condition reporting, specifying works, design proposals and the 
increasing areas of presentation. This continued application can best be illustrated by reference to a number of example projects. 
6, STONEHENGE 
Within English Heritage, Digital Photogrammetry was first introduced during a survey of the standing stones at 
Stonehenge, the World Heritage site located on Salisbury Plain in Wiltshire. 
This project, known as the ‘Mapping the Stones’ project, was to form the next phase within the rolling 
programme of data capture, data enhancement and public dissemination that has been developed on this 
important monument (Bryan et al, 1997). The project was to have two fundamental aims - to produce an accurate 
and complete photographic based archive of every standing stone forming the Henge and to generate three 
dimensional computer CAD based survey data on every visible external surface of each visible stone. 
Survey commenced in early 1994 with the acquisition 
on site of the required stereophotography and survey 
control of each visible stone. Around 671 stereo 
photographs were taken using a Wild P31 metric 
camera along with 1482 survey control observations using a Geotronics total 
station. The package was processed over the following two years utilising two 
digital photogrammetric workstations - the Helava DPW750 from Leica and the 
Phodis ST30 from Zeiss - to form the required series of computer based models. 
Each model comprised three dimensional point data, set out on a regular 2cm 
grid across each stone face. The co-ordinates were generated using the 
automatic image correlation feature of each workstation using scanned versions 
of the original stereo-photography. The 
resultant DEM’s appeared to fit the 
surfaces very well with only 10% of 
points requiring some form of editing 
especially within crevices and holes with heavy lichen growth. However a number of problems 
were encountered that collectively delayed progress on the project. The inability of each system to 
set up each stereomodel within a common co-ordinate system; the inability of the system at the 
time to carry out the required exterior orientations and the lack of suitable coverage around the 
edges of each stone. These days the majority of workstations are now able to deal with the first 
two problems within their standard orientation procedures. However precious few of the 
manufacturers saw Close Range Photogrammetry as a high profit market and so were reluctant to 
develop dedicated packages that can accommodate the wide variety of stereo-imagery and 
orientations commonly encountered in a typical close range project. 
Figure 5; Stereopair of Stone 3 
Figure 6: DEM of Stone 3 
In terms of applying digital photogrammetry to heritage conservation this project has become somewhat of a benchmark survey, certainly 
within the UK. It was one of the first heritage surveys to be tackled in England using digital photogrammetry and the lessons leamt have 
since been developed within other similar surveys as well as the standard specifications previously mentioned. In addition this unique 
survey material has demonstrated the potential of 3D survey for site visualisations, proving to be an essential component within ‘Virtual 
Stonehenge’ - the Virtual Reality model of the Henge that has recently been used to aid the redevelopment of the whole site. Within the