An underexpanded axisymmetric jet exhausting across an adjacent planar surface generates a unique flowfield that has received relatively little attention. To date, most research within this area has been motivated by acoustics, and consequently little flowfield data exist. This study aims to provide such a data set for an axisymmetric jet operating at a nozzle pressure ratio of five, and shows how variation in the plate-to-surface separation distance, h/Dj, results in large-scale changes in the flowfield. Planar particle image velocimetry (PIV) data, obtained on the jet symmetry plane, is complemented by schlieren imagery, surface oil flow visualization, and pressure-sensitive paint measurements. Results indicate that the flowfield is dominated by a shock/boundary layer interaction (SBLI) generated due to the presence of the plate, and that the SBLI subsequently alters the structure of the jet. The size, strength, and location of the SBLI vary as h/Dj increases. The data sets obtained in this study are inherently two-dimensional, necessitating interpretation to gain insight into the three-dimensional nature of this flow. To better understand the three-dimensional structure of this flow, a tomographic PIV system was used to obtain three-component velocity field data within a volume. Preliminary results from these measurements are presented herein.