how can i easily and quickly determine an object's distance from me, without a laser range finder, or the like

Question

i'm not too keen on sextants, astrolabes, slide rules, and their ilk, either. an accuracy of +/- 5 feet would be at the very outside of my desired knowledge. i know this might be impossible. rules of thumb are acceptable, but don't go overboard. thanks!

Answer 1

You can buy a cheap range finder that works with mirrors where you line up 2 images of the same object and read the distance from a scale. Another method would be if you know the height of an object... let's say another person... who is 2 meters tall, you can hold a ruler vertical at 0.5 meters away from your eye and measure the apparent height of the person on the ruler. The formula would be (distance) = 1/(ruler reading) in this case. This is a simple formula to use if you are looking at a 2 meter object and holding a ruler at 0.5 meters away, you would multiply 0.5 x 2 to get 1. You can use any objects but the math becomes more complicated if the values don't multiply to equal something even.

Answer 2

tape measure