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The paper presents a photogrammetric method for creation of developments of a Byzantine polychromy located on three apse walls of the cathedral church in Sandomierz. A big part of the polychromy is presently located behind a baroque altar, which was built in 18th century. The paintings behind the altar are either fully hidden by a brick wall, connected with altar, or hard to reach because of pillars and the cornice of the altar. Additional difficulties for photogrammetric measurements are caused by metal scaffolding elements situated close to the wall. To prepare the development of polychromy in a digital photoplan form of high resolution, and overcome the difficulties, a particular method of photogrammetric measurement was adopted. A digital camera Sony A900 (format 24x36mm) with objective of focal length 20mm assured maximum angle of view. Pictures of stereograms were taken with a calibrated digital camera Minolta Dynax 5D/f=20mm, from specially constructed vertical basis. Proper lighting was insured by a collar flash lamp Sigma EM 140 DG. Photogrammetric control points were measured from four levels of the scaffolding, and then transformed to one coordinate system, based on ground tie points (details of object), measured at least from two observation points. For surveying, the reflectorless total station TCR 407 Leica was used. Photoplans of development of the hard to reach fragments of the polychromy were made with a two stage method. In first stage, the development matrix was generated, based on stereo-measurements and photograms used in the stereograms. This matrix had proper geometry, but the quality of image was not good enough, because of wrong angle of the exposure axis relative to the wall surface. In second stage, photograms with the axis normal to the wall, were resampled into the basic matrix. Digital stereoplotter VSD, softwares: PI-calib, ImageAnalyst and MicroStation V8 were used for processing of high-resolution developments. For radiometric correction of the product, the program Photoshop CS2 was used.
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