Defining radial lens distortion

Radial lens distortion is the symmetric distortion caused by the lens due to imperfections in curvature when the lens was ground. In most cases, the errors introduced by radial lens distortion (around 1 to 2 um) are much smaller than the scanning resolution of the image (around 25um). Entering the values may significantly increase the processing time while contributing very little value to the final product. The values for radial lens distortion may be provided to you as R0 through R7 coefficients or in tabular format.

The equation for the lens distortion is:

delta r = R0 + R1*r + R2*r2 + R3*r3 + R4*r4 + R5*r5 + R6*r6+ R7*r7

where:

r: radial distance from the center of the image
R0 to R7: radial distortion coefficients

If you are using a USGS camera calibration report, the coefficients are given as K0, K1, K2, K3 and K4, which correspond to R1, R3, R5, and R7. K4 is discarded since it is usually zero.

The radial lens distortion parameter is optional and the coefficients may or may not appear in the camera calibration report.

Note: It is recommended that you obtain the radial lens distortion values for digital cameras. Because the manufacturing of digital cameras and their lenses is often not as precise as that for high-end photogrammetric cameras, the radial lens distortion tends to be higher.