What are those little yellow A-frame things along the roadside?

Factual Questions
1

I often see these little yellow signs that look like an A-frame along the roadside in rural areas. Actually they are about the size of and look like the roof of a birdhouse. They are yellow in color with numbers in black on both sides of the “roof”. They are usually mounted on a pipe a bit higher than a fencepost. At first I assumed the sides of the sign were tilted from the vertical to facilitate reading from an airplane, but the numbers aren’t that big - it would have to be a pretty low flyer to read the things.

So what are they and why the odd shape?

2

Pipeline markers? I realize that one’s orange, but the idea’s the same.

3

http://www.farwestcorrosion.com/images/fwst4/cars20.jpg

Look for “Aerial Patrol Marker” on this page.

4

they are pheremone-baited insect traps that entemologists use to catch specific bugs of interest

5

They are, indeed, markers intended to be read by aircraft as well as ground personnel. And yes, pipeline patrol craft do fly quite low.

Around here they seem to use helicopters more than airplanes, but I’m sure that varies from place to place.

6

That’s exactly what I see on the roadsides. Wow, I’d think you’d have to be flying at 200 ft or less to see the digits on those things.

Watch those wires, boys.

7

There is a requirement to have 20/20 vision for a commercial pilot’s license (either natural or corrected to that figure). Now you know one of the reasons why. :wink: