4.2.2. Experimental Results

We used the line or edge detection algorithm to extract the road in a typical scene; the detection results are shown in Figure 9.

**Figure 9.** The line detection results of a typical scene. (**a**) HiroshimaWest Airfield and (**b**) enlarged details.

Figure 9a shows the Hiroshima West Airfield. As seen in Figure 9b, the airfield runway had obvious periodic wavy patterns which were caused by short-period errors. The optical system of PRISM was affected by the motion of another sensor's mirror when this image was in the process of being captured, therefore, Step 3 of the proposed method was performed to deal with this image data. The partial details of the calibration results of a typical scene using the different methods are shown in Figure 10. The periodic wavy patterns in the calibration results of the proposed method are hardly recognizable in Figure 10a, but the periodic wavy patterns are easily recognized in the calibration results of the RFM method in Figure 10b.

**Figure 10.** Partial details of the calibration results for a typical scene. (**a**) Proposed method and (**b**) RFM method.

The calibration results of the two methods for 50 RCPs in typical scene are shown in Table 1, which shows that the mean value and RMSE of the calibrated results for the proposed method were less than those of the RFM method. The results of this experiment indicated that the proposed method did well in estimating the short-period components of equivalent bias angles when compared with the RFM method.


**Table 1.** Calibration results of the two methods using 50 RCPs in a typical scene.
