Laser range finder for measuring bridge height

[Marexetan]

Originally Posted by stimpsonjcat

You could just do the math once for a fixed forward distance...say 100 feet to the bridge, horizontally. Solve for angle from your boat to the height of your mast at 100 ft, then just check angle to the bridge when you are 100ft away and as long as the bottom of the span is above that, you're good.
Let's see...
Angle= ASIN(<mast height in feet>/100)
So for a 50ft mast at 100 ft that yields 30 degrees.

Mount something at 30 degrees from the horizon someplace on the boat, or get a bubble level and a friend, and sight along that when 100ft horizontally from the bridge. My acquaintance Sam loves to ask me to do the math in such cases. Here's a task he's solving for his son right here on https://essays.edubirdie.com/math he actually keeps it hidden from his son. I remember he wasn't strong in math at school, but he always could handle difficult situations.

You could also solve for how long the hypotenuse would be at that angle, mount the rangefinder at that angle, and check the distance when the bridge crosses the rangefinder.

The signs seem a lot easier, if present. ;P

I couldn't even guess about that. Thank you.

[Shrew]

Originally Posted by Bullshooter

Couldn't you just measure the distance to the underside of the bridge (hypotenuse) and the distance to the bridge base at your level height (one leg) and solve for the height using the Pythagorean theorem? (c2=a2+b2 > I couldn't do a superscript for "squared"). It seems like you could measure c and a when you were about 70 feet from the bridge and solve for b. Correct me if I'm wrong though.

To type SuperScript in a Forum

1) Type the first character or integer (e.g. "C")

2) Press and hold the <ALT> key, then type the decimal code 0178 using the number pad.

4) When you release the <alt> key, the number 2 should show up in superscript (e.g. c²)

https://www.webnots.com/alt-code-sho...and-subscript/

The old standard C^2 = C² has been around since print type was invented.