Eli5: how do rain gauges work and how accurate are they?
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At their very simplest, it’s just an open-topped container. Rain falls in and you just measure how much rain fell in. Even if it’s windy and rain isn’t falling straight down, as long as it’s not so bad water literally bounces off the inside of the gauge and out then it’s still accurate.
They’re reasonably accurate, as long as they’re out in the open. A lot of them will have wider openings to catch more rain and the markings are calibrated to account for that. They do it that way so there’s more rain hitting it so even if some water does bounce out after hitting the inside it’s a smaller percentage of the overall water collected, making the gauge a little more accurate.
The simplest versions are just a straight tube with a ruler printed on the side. 1″ of rain will fill the tube up 1″ and you just read that off the ruler.
You can mess with geometry (big opening, small tube) to make it more sensitive as long as you adjust the ruler to match properly.
They can be pretty accurate; a good digital gauge is good to 0.01″. A manual tube is only as good as the ruler & eyeball using it…down to 1/16″ of an inch is perfectly realistic.
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