We present a technique which combines time series of line-of-sight (LOS) velocity and electron density measurements from the Sondrestrom incoherent scatter radar (74.5¿ invariant latitude) to reconstruct the large-scale horizontal structure of the F region ionosphere during polar cap patch events. This reconstruction technique provides a new density-based means of examining patch morphology. Its wide region of coverage also facilitates comparison of radar measurements with other observational data sets. For two periods when patches were present and convection conditions in the nightside polar cap could be adequately approximated by the simple velocity model used in this initial implementation of the technique, we compare reconstructed radar data montages with in situ ion density data from DMSP satellites and 630.0 nm all-sky images taken at the radar site. The satellites data agree well with the radar reconstructions near the observation site, and show general agreement well beyond the radar field of view (FOV). Data from satellite passes to the east and west of the radar coverage suggest high densities were present over many hours of magnetic local time in the nightside polar cap. Many of the patches observed in the radar data were elongated perpendicular to the convective flow and may have extended well beyond the radar FOV. The characteristics of density enhancements observed by the satellites in the nightside auroral zone were found to be consistent with the creation of auroral zone blobs by distortion of patches seen exiting the polar cap in the radar data. Radar data reconstructions also show reasonable qualitative agreement with instantaneous 630.0 nm all-sky images regarding the location, size, and shape of patch features. In addition to validating the streamline-mapping technique, this result also lends support to previous optical studies of patch occurrence and morphology. ¿ 2000 American Geophysical Union