A method for retrieving a corrected spectrum from a measured spectrum (e.g., retrieving a top-of-water spectrum from a measured top-of-atmosphere spectrum) includes creating a scene-specific model of a region of interest and performing a ray-tracing simulation to simulate rays of light that would reach an airborne (or spaceborne) sensor. The region of interest can be an optically complex area such as an inland or coastal body of water. Based on the ray-tracing simulation, a scene-specific correction for unwanted effects (e.g., adjacency effects, variable atmospheric conditions, and/or other suitable effects) is obtained. A corrected spectrum is obtained by correcting the measured spectrum using the scene-specific correction. The ray-tracing simulation may be performed using a graphical processing unit, allowing the scene-specific correction to be performed in real time or near real time.