Photogrammetric Survey of Ancients Musical Instruments

Today’s violin makers try to replicate the characteristics of the best ancient instruments, such as Stradivari’s. To this aim, they need templates to replicate the soundboard with as much accuracy as possible. Despite several attempts, surveys with laser scanning did not produce usable results, because the instrument’s varnish coating gives rise to multi-path and reflections. Controlling illumination and using a projected pattern to get successful results from image correlation, a photogrammetric survey provided the requested accuracy, in the order of a tenth of a mm, although through careful survey planning and execution. The paper describes first of all the preliminary tests, focussed on trying to avoid spot reflections of the light sources and coping with the changes in the visual appearance of the violin texture from different standpoints by using a PC projector and random pattern. Method to assess the survey accuracy are also discussed. Finally, the results of a Garimberti violin surveyed in Cremona at the International Luthiery School “A. Stradivari” with a Nikon D70 are presented.