Table 1 Comparison of Zernike moment between the original and rotated images in two coordinates system
From: A new method based on stacked auto-encoders to identify abnormal weather radar echo images
Image feature | Original image | Rotation angle (°) | |||
|---|---|---|---|---|---|
30 | 45 | 60 | 90 | ||
Value in log-polar coordinate system | |||||
 Zernike moment | 1,775,000 | 1,543,900 | 1,563,000 | 1,578,700 | 1,325,600 |
 Normalized value | 1 | 0.87 | 0.88 | 0.89 | 0.75 |
 Difference value |  | 0.13 | − 0.01 | − 0.01 | 0.14 |
Value in Cartesian coordinate system | |||||
 Zernike moment | 5,257,300 | 3,423,600 | 3,188,100 | 3,748,300 | 3,298,300 |
 Normalized value | 1 | 0.65 | 0.61 | 0.71 | 0.63 |
 Difference value |  | 0.35 | 0.04 | − 0.11 | 0.09 |