Applying a Hough transform on original (top row) and filtered (bottom row) distance-time plots shows a more accurate EUV wave speed estimation in the latter case. The first column shows the distance-time plots. The second column shows the result of a Hough transform of the distance time plots for the first 100–250 Mm. The third column shows the “brightest” EUV wave detected, corresponding to a vertical feature caused by “flickering” in running difference images due to flaring in the top panel, and the actual EUV wave in the bottom panel. The last column displays all detected EUV wave segments projected on the distance-time plots.