In Carcassonne: The Land Surveyors, surveyors roam the countryside, changing the value of roads, cities, and monasteries when they're scored.
More specifically, you'll create a stack of surveyor tiles for each of these three landscape features, with one tile being active for each feature and one tile being the next in line. When at least one feature scores points for any player, you resolve everything based on the currently active tiles, then you place those tiles on the bottom of their stacks, making the next-in-tile of each type the active tile. Some tiles give you bonuses, others penalties, so time the scoring carefully while the surveyors are on your side!
This expansion was first released as a print-and-play through Hans im Glück.
—description from the publisher