'Czech Technical University in Prague - Central Library'
Doi
Abstract
This paper was presented at the CIPA 23rd International Symposium, 12 – 16 September 2011, Prague, Czech Republic:http://www.conferencepartners.cz/cipa/Cultural heritage is under a constant threat of damage or even destruction and comprehensive
and accurate recording is necessary to attenuate the risk of losing heritage or serve as basis for
reconstruction. Cost effective and easy to use methods are required to record cultural heritage, particularly
during a world recession, and close-range photogrammetry has proven potential in this area. Off-the-shelf
digital cameras can be used to rapidly acquire data at low cost, allowing non-experts to become involved.
Exterior orientation of the camera during exposure ideally needs to be established for every image,
traditionally requiring known coordinated target points. Establishing these points is time consuming and
costly and using targets can be often undesirable on sensitive sites. MEMS-based sensors can assist in
overcoming this problem by providing small-size and low-cost means to directly determine exterior
orientation for close-range photogrammetry. This paper describes development of an image-based
recording system, comprising an off-the-shelf digital SLR camera, a MEMS-based 3D orientation sensor and
a GPS antenna. All system components were assembled in a compact and rigid frame that allows calibration
of rotational and positional offsets between the components. The project involves collaboration between
English Heritage and Loughborough University and the intention is to assess the system’s achievable
accuracy and practicability in a heritage recording environment. Tests were conducted at Loughborough
University and a case study at St. Catherine’s Oratory on the Isle of Wight, UK. These demonstrate that the
data recorded by the system can indeed meet the accuracy requirements for heritage recording at medium
accuracy (1-4cm), with either a single or even no control points. As the recording system has been
configured with a focus on low-cost and easy-to-use components, it is believed to be suitable for heritage
recording by non-specialists. This offers the opportunity for lay people to become more involved in their
local heritage, an important aspiration identified by English Heritage. Recently, mobile phones
(smartphones) with integrated camera and MEMS-based orientation and positioning sensors have become
available. When orientation and position during camera exposure is extracted, these phones establish offthe-
shelf systems that can facilitate image-based recording with direct exterior orientation determination.
Due to their small size and low-cost they have potential to further enhance the involvement of lay-people in
heritage recording. The accuracy currently achievable will be presented also