Spatial Distortion Correction

The distorted data should be input in the normal manner (See Section 15.51, Page ). Before entering the calibration sub-menu the ROI may be defined if only a sub-region of the data is of interest³⁴ (using the REGION command, the PIXEL REGION command, or the IMAGE graphics sub-menu ZOOM IN graphics command). If only part of the data is of interest, defining a smaller ROI will save time. The correction will be applied throughout the ROI (provided the interpolating function is valid). If the ROI extents outside the valid region of the interpolating function, only the region within these limits will be corrected and the user will be informed of the limits.

Enter the calibration sub-menu using the command CALIBRATION. In general the command INPUT DISTORTION FUNCTION will be used to recover a previously calculated spatial distortion function. (If such a function has already been defined this is not necessary.)

The correction is applied to the data using the command SPATIAL CORRECTION. This re-bins all pixels in the current ROI and outputs them in the memory. This process may take several minutes for large images (further optimisation of this process is possible).

Having corrected the spatial distortion the result is in the memory, so after using EXIT to leave the calibration sub-menu, you should use EXCHANGE to make the corrected data the current data (this is the default option).