At this time Hosts do not currently have the ability to update the Nearby recommendations, as they are automatically suggested based on an algorithm we've built, but we hope to offer a feature for Hosts to recommend nearby places in the future.
Currently, we calculate these distances "as the crow flies." Think of it as if someone is on a road trip to your Hipcamp, we try to point out what's nearby so they can stop along the way.
We'd love it if you could add or vote for improvements to this system on our Hipcamp Host Transparent Roadmap where you can see what features we are working on and submit new ideas! Many other Hosts would love to weigh in on ideas and vote for them, which will help us prioritize changes. Here's some extra info on how to get involved with the roadmap if you'd like to read up on it!