Wikipedia quotes Campbell 2002 as saying:
Spatial resolution is defined as the pixel size of an image representing the size of the surface area (i.e. m2) being measured on the ground, determined by the sensors' instantaneous field of view (IFOV)
Geometric resolution refers to the satellite sensor's ability to effectively image a portion of the Earth's surface in a single pixel and is typically expressed in terms of Ground sample distance, or GSD. GSD is a term containing the overall optical and systemic noise sources and is useful for comparing how well one sensor can "see" an object on the ground within a single pixel. For example, the GSD of Landsat is ~30m, which means the smallest unit that maps to a single pixel within an image is ~30m x 30m. The latest commercial satellite (GeoEye 1) has a GSD of 0.41 m (effectively 0.5 m due to United States Government restrictions on civilian imaging). This compares to a 0.3 m resolution obtained by some early military film based Reconnaissance satellite such as Corona.
I'm confused by what the difference is between spatial and geometric resolution.
Is geometric resolution where a satellite image is said to resolve to 50cm, meaning that's the area on the ground that is sampled into a given pixel... And is spatial resolution defined along the lines of 1000x2000 pixels / square mile? Wikipedia's mention of "(i.e. m2)" makes me think the spatial resolution is defined in a square measurement of ground area, which is the same unit as geometric resolution, which gives me my confusion. Or would it just be said as a 1000x2000 pixel image, with no reference to ground size?