Creating a Record

“Creating a record of an historic building embraces a range of activities.  They are often overlapping and mutually informing.  In many circumstances choices will need to be made:  is a feature best captured by drawing, photography or a written description, or by a combination of the three?  The guiding principles should be accuracy, intelligibility and efficiency, together with a view of the purpose of the record.” (English Heritage, Understanding Historic Buildings, A guide to good recording practice, 2006)

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220 narrowvia dThe photomosaic methodology was developed in response to the specific needs of archaeologists excavating properties in Pompeii who wanted to document the fronts of entire city blocks as well as large buildings for study and project records. Recording the facades of properties in Pompeii presents several challenges:

  • Street widths are narrow, generally making it difficult or impossible to stand back far enough to adequately view an entire city block or large structures.
  • Extended wall lengths and heights make them difficult to measure and draw or photograph.
  • Walls and wall paintings can be easily damaged.

The restricted distances limit the ability of archaeologists to perform integrated visual examinations and analyses and to document structures graphically. Several alternatives were investigated to satisfy the needs of the projects.

Vertical planes of buildings, such as wall surfaces and doorways, can be architecturally represented by elevation drawings.  Elevations are usually drawn as orthographic projections, or as an object would be viewed from infinity thereby eliminating dimensional distortions.  Although orthographic projections are utilized extensively in new architectural designs, they are more difficult to produce for existing structures for several reasons:

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  • Surfaces must be carefully measured, recorded and drawn with appropriate detail.[1]
  • Archaeological elevations (commonly called wall drawings) must have, in addition, carefully measured and recorded information about other important details such as blocked doorways and multiple plaster layers.[2]
  • The process is time-consuming even when modern surveying equipment and computer aided drafting (CAD) software is used.
  • The final line drawings are usually monochromatic and have an artificial appearance.

Photography is a much more efficient recording method.[3] However, the technology has inherent limitations:

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  • Photographs usually depict perspective views.
  • Although photographs can accurately reflect color and detail, they may contain distortion because of camera tilt.
  • If a subject is photographed at too close a distance, only part of it will be recorded.
  • If a subject is photographed at too great a distance, detail will be sacrificed.
  • An object of known length (such as a graduated rod) must be photographed with the subject in order to convey its scale.
  • The scale of multiple photographs will vary unless each is taken at exactly the same distance from the subject.

Creating elevation drawings of the facades would be very time consuming, but more importantly, the finished product would lack color and detail.  The restricted distances make it impossible to record entire city blocks with one photograph.  A possible solution would be to take a number of photographs of the fronts of the buildings and combine them into one single, long image.  The objective would be to produce a photo-realistic and dimensionally accurate representation of the structures.  Between 2002 and 2004, a methodology was developed that combined the efficiency, color and realism of photography with the dimensional accuracy of a measured orthographic elevation drawing in order to achieve that objective.

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[1] John King, ed., Understanding Historic Buildings, A guide to good recording practice, Swindon:  English Heritage, 2006, pp. 8-12.

[2] Craig Spence, Archaeological Site Manual,   2nd edition,  London: Dept. of Urban Archaeology, The Museum of London, 1990, p. 3.3.

[3] King, Understanding Historic Buildings, A guide to good recording practice, pp. 8-12.