the time delay by the speed of sound we will define radius first ergo shell on which lining took place if we have three such measurements Center at different locations we will have three spherical shells the intersection of the three shells will pinpoint the thunderbolt right so photoacoustic CT in essence is a straightforward as this its triangulation right something we learned in middle school or high school right you can triangulate geometrically you can figure out the source right except in a real situation we don't have a