Here's a dumb idea:

- Take the most recent sale prices of all neighboring parcels within a quarter mile

- Take the land-area weighted average price per square foot

- Assess the given property as its land area times that average

Practically, this can be assessed without ever visiting any of the properties, and there are no games for either the assessors or the owners to play to manipulate it. Each neighbor serves as an example of the potential use (and therefore value) of local parcels. Yes, your hole-in-the-ground gets taxed the same as a skyscraper of the same size. Have you considered building something useful on it?

(Yes, as usual, parks, churches, and other non-economically-extractive community amenities would be exempt from _paying_ the tax, but that doesn't change the assessment)