Sub-pixel edge detection for photogrammetry using laplace difference of Gaussian and 4th order ENO interpolation

In modern photogrammetry for structure health monitoring, the detection of retro reflective targets, play a vital role in the accurate measurement of structural objects. However, due to the limitation of the resolution in photogrammetric equipment, a sufficient accuracy may not be achievable. While existing sub-pixel interpolation techniques may be used to overcome this limitation, they may produce unreliable results when presented with weak edge points. This paper presents a new sub-pixel edge detection algorithm namely, the ENO-LDoG method, which incorporates a high-order ENO interpolation scheme and a Laplace of a difference of Gaussian to accurately determine edge points. Experimental results on sample targets show that a higher precision can be achieved when compared to existing methods.