Here we present North American observations of the 3-dimensional structure of large-scale traveling ionospheric disturbances (TIDs) that affected the low- and mid-latitude ionosphere during the stormtime period of October 1--2, 2002. Using TEC data from the American network of dual-frequency GPS receivers, we are able to examine the effect of the TIDs on the background TEC and thus image their horizontal scales. Incoherent scatter radar data from the Arecibo Observatory give information on the vertical structure of the disturbances. The meridional and zonal structure of the TIDs are explored by computing the TEC perturbation, a method which has a resolution of a fraction of a TEC unit. The technique is effective in mapping the global structure of large-scale disturbances, as the lower latitude perturbations can be examined at the same time as the higher latitude sources. The method may prove valuable in studying the formation and propagation of TIDs.