A remote-sensing method for reconstructing the reconnection rate and the location of X-line from single-spacecraft observations developed recently is extended to a compressible plasma and an asymmetric magnetic field configuration. The method is based on the two-dimensional analytical model of time-dependent Petschek-type magnetic reconnection. The reconstruction technique is applied to a nightside flux transfer event recorded by Cluster spacecraft in the near-Earth magnetotail on 26 September 2005. The reconnection rate is found to be 3.7-4.8 mV/m; the reconnection distance is around 9-11 Re in the tail.