How do property surveyors figure out where to start?

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I think I can figure out once they have a reference point, how they could super accurately measure everything from there. But often times property disputes seem to come down to a matter of inches.

How does a surveyor know *this* spot is for sure correct and I can base the rest of the measurements on it? It seems like tiny errors over many plots of land could add up to being off by several feet.

In: Engineering
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In the UK at least there are numerous trig points set up throughout the country and surveyors will work back from one of those to create their own reference point within the site.

There’s a system with a small number of level-1 markers in a country and then many more level-2 markers based on those, and so on. By the time local land surveyors do their job they’re using level-4 or -5 markers which can be just plaques set in the curbs. They have access to a database giving the positions of the markers. Unless some gross error comes to light, these markers are considered accurate enough for property disputes.

Everything you said is true, and surveyors have to consider it. There are survey markers (monuments) scattered around that serve as reference points. When a surveyor starts a new survey, they’ll place a GPS receiver on it for several hours to get as good a fix as possible before basing the rest of the survey from that point. They’re not *that* ubiquitous though, so you kinda have to daisy-chain points that aren’t in line-of-sight to the monument. That does accumulate error, and there are limits to what is acceptable.

My dad’s a land surveyor practicing in the state of Georgia. It’s been a while since I worked with him. Somebody with a license or more recent experience can probably give a better answer.

others have answered how surveyors work so I’ll just add

> It seems like tiny errors over many plots of land could add up to being off by several feet.

it’s rare for them to be that far off, but the law actually has stipulations to deal with things like this. if you treat an area as part of your property in good faith (meaning you honestly and reasonably believed you had the right to) and the rightful owner of that land doesn’t contest it for an extended period, you can be granted the legal right to continue to use that land (called an easement), if not gain ownership of it outright.

this is fairly common in suburbia, where fences and parts of driveways can extend into neighboring properties.

In what you’re describing, you’re trying to make a whole pie from slices of pie with all the little crumbs and cuts along the edges butting up against each other; it’s messy. Surveyors bake pies and then precisely slice them up; they seek to know the “whole” and are then able to precisely determine the “parts”. Surveyors won’t start at your rear lot line to measure the block. They’ll measure the block and then determine where your lot line is in relation to the block.