8
matrix can be calculated to align the current image to the
previous one. Starting from the first one, the frames can be
aligned and stitched one by one to get the stitched image
of a borehole. One segment of a stitched borehole image is
shown (see Figure 11). It can be found that, even without
blending, the geological features can be easily identified in
the stitched image. Researchers at the National Institute
for Occupational Safety and Health (NIOSH) are work-
ing on improved methodologies involving the stitching of
borescope images to ultimately have a vertical image with-
out the offset (see Figure 11). After image straightening, a
measurement scale can be applied to the image so that the
images could be directly used in a geological cross section.
Figure 7. The original images for stitching
Figure 9. All matches of key points that were detected.
Figure 8. Key points that were detected with the ORB
algorithm
Figure 10. Filtered matches of key points between two
images