Fig. 1. Camera model

Fig. 2. Schematic of calibration principle

Fig. 3. Geometrical relationship of plane measurement

Fig. 4. (a) Distribution of measurement precision of different positions in the measuring area; (b) distribution of measurement precision versus xM, when yM=-500 mm; (c) distribution of measurement precision versus yM, when xM=0 mm

Fig. 5. Measurement precision versus camera angles

Fig. 6. Experimental setup

Fig. 7. Target images. (a) First group; (b) second group

Fig. 8. Schematic of precision measurement experiment. (a) Measuring planes; (b) positions of small targets; (c) feature point intervals of a small target

Fig. 9. Measurement error of different positions on 0 mm plane. (a) Absolute error; (b) relative error

Fig. 10. Measurement error of different positions on 100 mm plane. (a) Absolute error; (b) relative error

Fig. 11. Measurement error of different positions on 200 mm plane. (a) Absolute error; (b) relative error

Fig. 12. Relationship between total measurement error and distance of different planes using multi-target method. (a) Absolute error; (b) relative error

Fig. 13. Measurement error distribution of different planes using multi-target method. (a) Absolute error; (b) relative error

Fig. 14. Error of XM and YM axes in different positions on the 50 mm plane. (a) Absolute error; (b) relative error