Not all assessors do this accurately, especially in California, but there are many that do. This article includes a section on land valuation which summarizes and links out to various other articles about various approaches

https://www.astralcodexten.com/p/does-georgism-work-five-yea...

> In its ideal form, this tax would capture and redistribute the annual rental value of land; that is, the recurring value of the land excluding the value of any buildings or other improvements on top of it.

> but you see the same basic patterns everywhere. Land in the city center is worth much, much more than outlying areas.

The calculation of the "unimproved value" always perplexed me.. it seems like you're not taxed for the things you build on your land, but instead for the things other people built around your land. After all, why would property in a city be valuable if not for all the high rises, subways, and office buildings?