Evaluation and calibration of X-Y-coordinatographs used in cephalometric analysis

The aim of this investigation was to clarify some of the sources of error inherent in coordinatographs and to establish a suitable method of calibrating these instruments. Using a test grid standard measurements were made and parameters for both systematic and random errors calculated. For the instrument employed small but significant errors were recorded for scale error, orthogonal error and X-axis play. Operator and instrument precision were also determined. It is concluded that regular testing of coordinatographs used in research is necessary if suitable calibration of systematic errors and a control over wear and tear is to be achieved.