The well-known positions of the Bursting Pulsar (GROJ1744-28) and the soft gamma repeater SGR1806-20 represent “space truth” data (the equivalent of “ground truth” data in remote sensing) which can be used to verify the accuracy of the IPN location technique. About 500 bursts from GROJ1744-28, and several dozen bursts from SGR1806-20, have been observed jointly by BATSE and Ulysses. Using these data, we have been able to verify the timing accuracy of the Ulysses data in numerous spacecraft and experiment operating modes, the cross-correlation technique used to compare the light curves of gamma-ray bursts from different spacecraft, and the method used to derive burst positions by triangulation. We show that the uncertainties in the triangulation technique are dominated by count rate statistics, and that no systematic errors exist whose magnitude is comparable to the statistical errors. ©1998 American Institute of Physics.