To better discern directions, she specifically bought a "road map." She had spent quite some time studying it before she could understand, but having the map alone wasn't enough, she also needed to be able to discern directions, so trees were planted on both sides of the official road, helping to identify the road's direction.
These trees served two purposes: one was to provide shade and a cool retreat for passersby, and the other was to mark the road's course. Consequently, as long as they followed the regularly arranged trees, they hardly strayed from their path.
As for determining how far they had traveled, in Yan Country, the government erected stations at regular intervals along the main official road, which served government officials, similar to the service areas on our modern highways, while the official road was akin to the highways of this era.
