For land assessment, many countries or municipalities assess it regularly. In my country (New Zealand), most city councils re-assess land value and improvements value every three years (and charge council rates based on them).
I live on around 80 acres (30 hectares?). Our land is a bit unique in the area, and in general there hasn't been a single piece of land sold near us since before the pandemic and all the economic change that came with it. I don't know how the county could possibly know what our land is worth until something similar sells on the open market again.