The method of isolines for the shower axis determination
  The method of isolines (contours) is proposed to be used for deter- mination of core location of extensive air shower on the array plane. As variable z=f(x,y) are used flux densities of particles, registrated from ground detectors. Obtained isolines are approximated with circles, which centers show impact point of shower axis. The method was demostrated on experimental data from Tien-Shan shower array in period 1974-82. The possibilities and difficulties of the method are discussed. 
I.N.Kirov, J.N. Stamenov