It is entirely possible and is not infrequently done. There are certain cases where it's fairly common. One is when there is a need to establish the value tha

It is entirely possible and is not infrequently done. There are certain cases where it's fairly common. One is when there is a need to establish the value that a piece of land had at a certain time in the past before an improvement was made (e.g., to determine what tax liability existed at that time, or how assets were distributed among partners or heirs). Another is when someone needs an appraisal that separates the land and the improvements in order to convince someone to give them a loan to do something with the land that will involve getting rid of whatever's already built on it. This can happen for instance when there is an "underutilized" piece of land (e.g., a one-story building in a dense urban area). It's true that determining the value of the unimproved land is not an exact science, but that is true of real estate appraisal in general.