Line positioning based on HT error compensation

The discretization of a HT space results in the ρ value detection error of a line. This paper addresses the ρ-direction precision improvement by compensating for this error. The mage are vertically or horizontally shifted, and a series peak positions are obtained by applying the standard HT (SHT) on these shifted images. The change of ρ value of a line due to these shifts is studied. On one hand this change can be measured by detecting the peak shift in HT space, on the other hand it can be obtained by geometric analysis on the vertical or horizontal shift in image space. The difference between the unit change in HT space (i.e. the ρ-direction resolution Δρ) and the unit change in image space (i.e. ρ value change due to vertical or horizontal unit shift) is used to measure the SHT ρ value detection error. A high precision ρ value is obtained by compensating for this error. The experiments show the effectiveness of the proposed method.