How far can the party see?
I've been noodling around with a STALKER inspired OSR game, which has had me thinking about sightlines for hex crawls. For my purposes I've been using 3 mile hexes because so much of the maths around hiking works out well.
With 20:20 vision you can spot a person as a dot for about 1.5 miles (½ hex) and a 6ft square object (e.g. a car) for about 3 miles (1 hex). With a scope you can theoretically make out details at magnification X that distance (but you'd need sufficient elevation and clear weather).
You can see further when higher up (or when the thing you're looking at is higher up).
Assuming flat ground and a clear day, here's how far you can see the ground from different heights:
| Height | Equivalent to | Horizon Distance | Looking out a window on the... |
|---|---|---|---|
| 1-3 ft | Lying Prone / Crouching | ~ 1.5 miles (0.5 hex) | Ground floor |
| 6 ft | Standing | ~ 3 miles (1 hex) | Ground floor |
| 12 ft | Standing on a car | ~ 4.5 miles (1.5 hex) | 2nd floor |
| 30ft | Roof of a two storey house / top of a telephone pole | ~ 6 miles (2 hexes) | 3rd floor |
| 90ft | Water tower / church steeple | ~ 12 miles (4 hexes) | 9th floor |
You can assume every 30ft of additional elevation (approximately 3 stories) will let you see another 3 miles (1 hex).
The same is true for the thing you're looking at. The same values work if you're at ground level and your target is at the given height.
If you want to check if the party can see something that is at a different height, add together the respective distances to the horizon for the party and their target. If that sum is greater than the distance the party is from the object, they can see it.
If you're wondering, the effects of atmospheric haze on a perfect day would be minimal, with elevation being the limiting factor. On a perfect day you could see 150 miles, so you'd need to be at a height of about 15,000 feet looking at the ground at sea level before it starts to become a problem.
