As per wikipedia angular resolution is the ability of device to capture minute details of an object and is the same definition in case of spatial resolution.
Whats the difference Between Angular Resolution and Spatial Resolution of optical device(Camera)?
Whats the relation between these two resolution?
Assuming we are talking about resolution in object space (where the the camera is looking towards), the difference is just in how the objects are described. If several objects are located at infinity, spaced (say) 1 degree apart, and just resolved, then one would say the resolution is 1 degree.
But if objects are located 35 mm apart, at a distance of 2000 mm, then each object occupies 1 degree. If the objects are just resolved, you could say the resolution is 1 degree in angular terms, or you could say the spatial resolution is 35 mm at 2000 mm distance. Usually, but not always, angular resolution implies the objects are at infinity. Spatial resolution implies the objects are nearby.
If the distance to the object is greater than about 10 times the focal length, the angular resolution for most lenses will not change much with distance, and it would be sufficient to describe the lens resolution only in angular terms.
As a warning - sometimes the spatial resolution describes the resolution at the image plane. If this is done, they should be explicit about it. For objects very far away from a lens, the relation between the angle in object space and the size of the image at the image plane is h=f*tan(theta). So for example, a 100 mm focal length lens, imaging an object that occupies 1 degree, will form an image that is 1.7 mm high at the image plane.
The relationship between the two is that at the focal plane of the instrument there will be a certain number of microns per arcsecond (or whatever your favourite units are).
This ratio is set by the optics of the camera - particularly its focal length.
There can be a difference though that trumps this conversion factor, if there is a mismatch between the pixel size in the focal plane and the angular resolution. You can talk about the angular resolution of a camera independently of the detector. To properly sample the angular resolution then you need at least 2 pixels covering the angular FWHM of a point source. If there are fewer, then the angular and spatial resolution of the camera+detector system as a whole will be at least whatever two pixels corresponds to in angular or spatial terms.
Sometimes, spatial resolution will instead refer to the ability to resolve two objects of a given separation at a given distance. e.g. HST can resolve two objects 190m apart on the Moon. In this case it is really just converting an angular resolution of 0.1 arcsecond, which is set by the fact that two pixels in the HST plane corresponds to 0.1 arcseconds on the sky, by multiplying it (in radians) by the distance to the Moon.
