How do you measure spatial resolution?

Spatial resolution is typically measured by the smallest distinguishable detail in an image or representation, often quantified in units such as pixels per inch (PPI) or dots per inch (DPI). In remote sensing, it can also refer to the ground sample distance (GSD), indicating the size of the smallest object that can be detected on the ground. Higher spatial resolution means finer detail and greater clarity in the representation of spatial features. In medical imaging, it may be assessed through metrics that evaluate the ability to distinguish between closely spaced structures.