The ground effects of propellers have been extensively studied in the literature both theoretically and experimentally via a variety of methods; however, there are limitations with regards to global analyses of the mean and unsteady flow along the surface of the ground plate. This study provides a proof of concept that back-imaged pressure-sensitive paint (PSP) can successfully analyze the mean and unsteady surface pressure distributions along such a ground plate. In particular, the unsteady nature of the pressure field was successfully measured utilizing this technique. By analyzing the pressure field in the frequency domain, the unsteady characteristics of the flow were able to be quantitatively determined. In particular, the PSP-derived power spectral density of the surface pressure fluctuations show primary peaks at a frequency which agrees both with the theoretical predicted blade rotation and the spectral results calculated from the supplementary Kulite pressure sensors. The amplitude of this primary spectral peak is then shown globally at every PSP pixel location, which showed a clear low-amplitude region near the center of the blade radius, and a clear maximum-amplitude ring located at approximately 75% of the blade radius. Lastly, the concavity of this spectral amplitude profile changed signs near the blade-radius percent where previous works by the authors qualitatively measured a dividing streamline between primarily tangential flow and radial flow. These data provide a promising area for potential use of PSP to more fully understand the flowfield under rotor blades in ground effect, thereby improving safety and performance. © 2024 by Carson L. Running. Published by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.