Classical triangulation techniques determine the impact point by capturing the Time of Arrival (TOA) delays of some elastic waves at different sensor locations. This paper presents an impact localization technique that exploits the low frequency content of the global vibration response. A modal signature of the impact location is described instead of a time signature based on the TOAs. The proposed approach uses the simple idea that the vibration modes of a structure are not excited in the same proportions depending on impact location. The proposed method is applied to a large aircraft composite panel equipped with a sparse distribution of accelerometers. An experimental modal analysis was performed prior to the impact tests to identify the first low frequency vibration modes of the structure within 10-50Hz. The results of the study show that the technique succesfully localizes impacts applied at any location on the panel.