How do surveyors determine where a property line is at when they get to a new property? Do they just use landmarks like trees and drive ways to determine the property line? What’s the difference between me taking a few wooden stakes and orange flags and just saying that’s my property line opposed to an official surveyor?
I imagine there is a process they go through to determine the exact measurements of the property but what is it?
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The funky optical devices (usually yellow) on the tripods are called theodolites** – basically they measure distance and angles from where they are very accurately. And it can use GPS as a backup location assist.
So there will be some known spot. Maybe a manhole cover for the sewer. The city knows exactly where that is in relation to… well whatever they use as an origin for measurement. City hall, who knows. The location of that manhole is know to within the inch. From there they use and move the theodolyte and the stick (for the other end of the distance being measured) to mark out where exactly the boundary of your property is according to the map of your street or development on file. Street and subdevelopment plans, accurately plotting every plot and street and utility line have been filed somewhere at city hall and are required before any work can get done.
The reason the city keeps track is because they have to. Whups, we need to move this sewer. Can we move it a foot north? Nope, it’ll run through /u/zeek1999’s lot so now we have to get his permission. And for knowing where stuff is for safety (call before you dig etc.)
** so they know where they are right? Or you tell it where it is. The manhole cover lets say. The other surveyor goes over to some place and holds the stick – the theodolite shoots a pulse of light, it bounces off the stick – using the delay, it measures distance. Meanwhile you’ve calibrated the device to a particular origin bearing and very accurate angle measurement is built in. So if you know a distance and the angles from some reference bearing you can accurately measure anywhere in sight from your known reference point.
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