how can the coordinates of an intersection point of a cross

[jodel]

there is a cross on a chart and i need the coordinates of the intersection point as a reference for further measurements

[BruceAmmons]

The simplest way is pattern matching. Train the routine with the cross, then search for it. It should always be within about 1 pixel of the intersection. You can use sub-pixel accuracy to improve the results sometimes.

To improve the pattern matching results, you can use edge or peak finding routines to find the horizontal and vertical lines that make up the cross. You can determine the center from these lines.

Bruce