Hacker News new | ask | show | jobs
by danielsamuels 132 days ago
The website claims the longest line of sight in my city is 24.7km from someone's garden that is surrounded by houses. I walk past this particular spot on my way to the gym. I walk downhill from my house to get there. I seriously question the reliability of this data.
2 comments
tombh 132 days ago
The resolution of the underlying data is only ~100m. So most houses, vegetation, etc, gets blurred into the same smooth surface. There are actually higher resolution data sets, even up to centimetre scale, using LiDAR, of cities. We'd love to integrate these but it's a few orders of magnitude more data.
link
DiggyJohnson 132 days ago
I think you're assuming more fidelity than the project is claiming
link
danielsamuels 132 days ago
I'm assuming that when the project says you can see 24 km from a given location, that you can see 24 km from that location. That's not the case. Fundamentally, it doesn't do what it claims to do.

Why allow the user to select any arbitrary location on a map and give an answer when you know the answer is most likely nonsense? You don't need to compute for 2 days to accomplish that; you could just make it up.

link
crazygringo 132 days ago
Surely you understand it's based on limited resolution data, and therefore intended to be used at the scale of general topography like mountains and valleys?

That it's not taking into account human construction or distances of tens of meters?

Presumably you can walk a little bit and climb on someone's roof to see the claimed 24.7 km. Assuming a sufficiently clear atmosphere, and that there isn't a tall office building in the way or something.

link
wat10000 131 days ago
Why not complain that there's a point inside somebody's basement and you can't see any distance from that? Why not complain that it's wrong any time you close your eyes? Those would be about as sensible.
link
danielsamuels 131 days ago
Ironically, the site would probably say you can see 20 km from inside the basement.
link
wat10000 131 days ago
What's ironic about that? Of course it would. It's working off of large-scale terrain features, not structures. It will also tell you that you can see distant mountains when it's cloudy or you don't have your glasses on.
link