Certification of climb performance has traditionally been accomplished using reciprocal heading climbs. This was done to eliminate wind gradient effects. However, the FAA allows climb certification to be done on a single heading when inertial methods are used. A method was developed utilizing a DGPS system that allows an engineer to apply the inertial corrections to a single climb without the need of INS equipment. This method has been validated on several aircraft by comparing conventional reciprocal heading climb results to results obtained using the GPS method on the same climbs. The GPS climb method presented here can potentially reduce the number of climbs required for development and certification as well as provide more consistent data.