"Chip Time" versus "Gun Time"
The 2007 USATF Rule 245.1 states "The order in which the athletes cross the finish line will be the official finish position." Further, Rule 245.3 - regarding transponder timing - "the actual time elapsed between an athlete reaching the starting line and finish line can be made known to the athlete, but will not be considered as official time." In short, official time per USATF rule is gun time.
Also, USATF Rule 165.16 covers the use of transponder timing systems (i.e., the chip) and Rule 165.16(h) states that "times for other competitors will be adjusted, based on the official winning time." In other words, "chip" timing cannot be used for official time(s) nor records unless the "chip" time is properly adjusted (i.e., gun time) except for LDR Masters age group records if the record setter wins his/her age group and the timing mats are properly placed before the start line and after the finish line (Rule 265.10).