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they are designed for the relatively consistent exposure 
conditions of aerial photography, but also because the 
operators are generally photogramme trists rather than 
scanning specialists. It has been found that it is possible to 
use Kodak PhotoCD as an alternative to dedicated 
photogrammetric scanning. (Thomas, Mills and Newton 
1995). This system has been used by the English Heritage 
Metric Survey Team to improve colour balance in 
orthophotograhs (Clowes 2002). 
6.2 True Colour 
When studying the decoration of one floor it will usually be 
acceptable to have each colour reproduced consistently as 
long as the colours look approximately correct. When 
comparing two or more examples or where a floor is likely to 
be re-buried after excavation it will be desirable to reproduce 
the true colour of the decoration as accurately as possible. 
In order to give an exact representation of the colours of a 
floor it is necessary to have a way of measuring those 
colours. This could possibly be achieved by recording the 
colours of the individual components of the floor using a 
colour measurement device. However, the number of 
different colours typically found in an historic floor would 
make this impractical. Even a mosaic made up of, say three 
different colours, will exhibit variations due to changes in the 
natural materials. 
A more feasible approach is to place a standard colour chart, 
such as a Macbeth chart, in each photograph (see Fig.l). The 
colours of the individual elements in the chart can then be 
measured and corrected throughout the process. Each process 
and piece of equipment used will have its own effect on the 
colour so individual colour profiles are required for digital 
cameras, scanners, monitors, printers and even the type of 
paper used. Even then the colour rendition will only be 
correct if the final product is viewed under the same lighting 
conditions as the original. This is almost impossible to 
achieve because the reaction of the eyes to the lighting of a 
subject is also affected by the colour and lighting of the 
surroundings. The general aim is to reproduce the colour as 
accurately as possible but with the caveat that it will never be 
absolutely correct. 
7. CONCLUSIONS 
Mosaic, tiled and other decorative floors are a valuable part 
of our cultural heritage which should be conserved and 
recorded for future generations. A photographic approach is 
the most useful and is the only practical way of recording the 
many textural variations exhibited by most historic floors. 
Floors are usually quite flat and so can be successfully 
recorded using the relatively cheap and accessible method of 
rectified photography. Some floors, are however quite 
undulating and so warrant the application of 
orthophotography. The use of orthophotography although 
more expensive provides added value in the associated 
products such as contour maps. Colour balance is important 
if an acceptable looking product is to be produced. Correct 
representation of colour is important to some users but 
actually very difficult to achieve. It is also difficult to know if 
it has been achieved. 
8. REFERENCES 
Clowes, M., 1997. Mosaicing the Mosaic - Roman restoration goes digital. Surveying World, May/June 1997, pp 36-37 
Clowes, M., 2002. Digital Photogrammetry at English Heritage: a Pictorial Review of Projects to Date. Photogrammetric Record, 
17(99), pp 441-452. 
Dallas, R. in Fawcett, J., 1998. Historic Floors: Their History and Conservation. Butterworth Heinemann, Oxford, pp 91. 
Fawcett, J., 1998. Historic Floors: Their History and Conservation. Butterworth Heinemann, Oxford, pp 2. 
Hunt, R.W.G., 1995. The Reproduction of Colour. Fountain Press, Kingston-upon-Thames, pp 71. 
Thomas, P.R., Mills, J.P., Newton, I., 1995. An Investigation into the Use of Kodak Photo CD for Digital Photogrammetry. 
Photogrammetric Record, 15(86), pp301-314.