# Is a point a shared border?
**URL:** https://boards.straightdope.com/t/is-a-point-a-shared-border/982100
**Category:** In My Humble Opinion
**Created:** [April 3, 2023, 8:07pm UTC](https://boards.straightdope.com/t/is-a-point-a-shared-border/982100 "2023-04-03T20:07:40Z")
**Posts on this page:** 15
**Page:** 1
### Author:  [@enipla](https://boards.straightdope.com/u/enipla)
#### Post date: [April 3, 2023, 8:07pm UTC](https://boards.straightdope.com/t/is-a-point-a-shared-border/982100/1 "2023-04-03T20:07:40Z")
Am having a rather esoteric friendly debate with co-workers.
If a property(land) is described as having a point (corner) with another property point (corner) with the exact same coordinates, is that a shared boundary/border?
Or must it be linear, such as a property line, or state or country line.
I’m thinking it is a shared ‘boundary’, not a ‘border’ It works both ways really. I could argue either way. It’s semantics all the way down.
One guy, a really sharp programmer said of course because a point has dimensions (dude, really??). Well, no it does not. A defined point (used in mapping and math) has no dimensions, it is different than a monument on the ground, which does, have dimensions. A monument is a physical thing.
I’m in GIS. I don’t think I’ve ever seen a deed that would say that a shared point, is a shared boundary/border.
This came from a trivia question about the four corners - Colorado, Utah, Arizona, New Mexico. Does Arizona share a border with Colorado? It’s a point.
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### Author:  [@Ynnad](https://boards.straightdope.com/u/Ynnad)
#### Post date: [April 3, 2023, 8:12pm UTC](https://boards.straightdope.com/t/is-a-point-a-shared-border/982100/2 "2023-04-03T20:12:07Z")
This is a very controversial question in some contexts. See the following for just one example.
> **[Corner Crossing - The American Surveyor](https://amerisurv.com/2023/02/09/corner-crossing/)**
>
> In October of 2021 four hunters travelled down Rattlesnake Pass Road in Carbon County, Wyoming…
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### Author:  [@enipla](https://boards.straightdope.com/u/enipla)
#### Post date: [April 3, 2023, 8:24pm UTC](https://boards.straightdope.com/t/is-a-point-a-shared-border/982100/3 "2023-04-03T20:24:05Z")
> [@Ynnad](#):
>
> This is a very controversial question in some contexts. See the following for just one example.
Yep, had seen that. It’s really quite stupid really. Thanks for posting that link though. Forgot about it.
Really the Four Corners, is just a tourist trap (of sorts). My Wife and I went once because our travels took us real close and we said ‘might as well’.
Surveying is a very odd animal as well and depends on history and Prescriptive rights and all manner of wrenches that can be thrown in the works. The accuracy of surveying 20 years ago is a very different animal than today. Let alone 100 years ago. Accepted previously marked property corners are generally accepted. But can make a real mess all around.
In the County I work for, there is a ‘Bearing Tree Road’. That was because surveyors took there bearings off of that tree. That tree is long, long gone.
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### Author:  [@TriPolar](https://boards.straightdope.com/u/TriPolar)
#### Post date: [April 3, 2023, 8:49pm UTC](https://boards.straightdope.com/t/is-a-point-a-shared-border/982100/4 "2023-04-03T20:49:18Z")
Doesn’t count as a border for the Four Color Map problem.
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### Author:  [@N9IWP](https://boards.straightdope.com/u/N9IWP)
#### Post date: [April 3, 2023, 8:59pm UTC](https://boards.straightdope.com/t/is-a-point-a-shared-border/982100/5 "2023-04-03T20:59:17Z")
They adjacent for the Manifest Destiny board game
> **[Manifest Destiny](https://boardgamegeek.com/boardgame/12283/manifest-destiny)**
>
> Guide North America through times from colonial era to the present.
10.1 “Territories that are connected at one of its corners, including the four-corner space, are considered adjacent”
Brian
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### Author:  [@enipla](https://boards.straightdope.com/u/enipla)
#### Post date: [April 3, 2023, 9:02pm UTC](https://boards.straightdope.com/t/is-a-point-a-shared-border/982100/6 "2023-04-03T21:02:10Z")
> [@TriPolar](#):
>
> Doesn’t count as a border for the Four Color Map problem.
Interesting and embarrassing. Never heard of that.
We do thematic maps based on attributes of the polygons. Click, click, click and Bob’s your uncle.
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### Author:  [@enipla](https://boards.straightdope.com/u/enipla)
#### Post date: [April 3, 2023, 9:03pm UTC](https://boards.straightdope.com/t/is-a-point-a-shared-border/982100/7 "2023-04-03T21:03:05Z")
> [@N9IWP](#):
>
> “Territories that are connected at one of its corners, including the four-corner space, are considered adjacent”
That’s a good word for it.
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### Author:  [@Thudlow\_Boink](https://boards.straightdope.com/u/Thudlow_Boink)
#### Post date: [April 3, 2023, 10:15pm UTC](https://boards.straightdope.com/t/is-a-point-a-shared-border/982100/8 "2023-04-03T22:15:57Z")
> [@TriPolar](#):
>
> Doesn’t count as a border for the Four Color Map problem.
Yes, that was the first thing I thought of.
And I notice that the very second sentence of the [Wikipedia article](https://en.wikipedia.org/wiki/Four_color_theorem) states:
> [@](#):
>
> _Adjacent_ means that two regions share a common boundary curve segment, not merely a corner where three or more regions meet.
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### Author:  [@Kent\_Clark](https://boards.straightdope.com/u/Kent_Clark)
#### Post date: [April 3, 2023, 10:20pm UTC](https://boards.straightdope.com/t/is-a-point-a-shared-border/982100/9 "2023-04-03T22:20:40Z")
> [@Thudlow\_Boink](#):
>
> _Adjacent_ means that two regions share a common boundary curve segment, not merely a corner where three or more regions meet.
Nonsense. I can step directly from Arizona to Colorado without passing through another state. If that isn’t “adjacent” then the word needs to be redefined.
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### Author:  [@Chronos](https://boards.straightdope.com/u/Chronos)
#### Post date: [April 3, 2023, 10:42pm UTC](https://boards.straightdope.com/t/is-a-point-a-shared-border/982100/10 "2023-04-03T22:42:46Z")
> [@Kent\_Clark](#):
>
> Nonsense. I can step directly from Arizona to Colorado without passing through another state.
You might not step in any other state, but unless you’re very skinny you’ll pass through them.
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### Author:  [@TriPolar](https://boards.straightdope.com/u/TriPolar)
#### Post date: [April 3, 2023, 10:44pm UTC](https://boards.straightdope.com/t/is-a-point-a-shared-border/982100/11 "2023-04-03T22:44:17Z")
Unless you are infinitesimally thin then you have to pass over one or both of the other states at the corner.
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### Author:  [@enipla](https://boards.straightdope.com/u/enipla)
#### Post date: [April 4, 2023, 12:25pm UTC](https://boards.straightdope.com/t/is-a-point-a-shared-border/982100/12 "2023-04-04T12:25:14Z")
OP here, my Wife is an appraiser. I asked her how an appraiser would describe one property that shares one point with another (not linear).
She said they call it touching. 🤷♂️
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### Author:  [@Peter\_Morris](https://boards.straightdope.com/u/Peter_Morris)
#### Post date: [April 7, 2023, 5:39am UTC](https://boards.straightdope.com/t/is-a-point-a-shared-border/982100/13 "2023-04-07T05:39:26Z")
> [@Thudlow\_Boink](#):
>
> And I notice that the very second sentence of the [Wikipedia article](https://en.wikipedia.org/wiki/Four_color_theorem) states:
>
> > [@](#):
> >
> > _Adjacent_ means that two regions share a common boundary curve segment, not merely a corner where **three** or more regions meet.
“ **Three** ”? Shouldn’t it be **four**?
I mean, if three areas meet at a point, all of them will border the other two. But with four or more, there will be several pairs with no border except the point.
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### Author:  [@jjakucyk](https://boards.straightdope.com/u/jjakucyk)
#### Post date: [April 7, 2023, 12:42pm UTC](https://boards.straightdope.com/t/is-a-point-a-shared-border/982100/14 "2023-04-07T12:42:01Z")
> [@Chronos](#):
>
> > [@Kent\_Clark](#):
> >
> > Nonsense. I can step directly from Arizona to Colorado without passing through another state.
>
> You might not step in any other state, but unless you’re very skinny you’ll pass through them.
And that is the exact problem with corner crossing. A border isn’t just a horizontal line/arc, it’s a vertical plane too. So as @TriPolar said, unless you’re infinitesimally thin then you’re still passing through the other states. Those states could put up fences that meet in the corner, and thus you have no way to get through without going up and over with a ladder or something, but you’re still then “trespassing” in a sort of “I’m not touching you, I’m not touching you” way. Air-drops from helicopters have been done, because these borders don’t go up forever into space, but for all practical purposes they may as well.
So to circle back to the OP, it’s not so much a point as it is an intersection of vertical planes. I don’t know if it really changes anything though.
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### Author:  [@enipla](https://boards.straightdope.com/u/enipla)
#### Post date: [April 7, 2023, 1:47pm UTC](https://boards.straightdope.com/t/is-a-point-a-shared-border/982100/15 "2023-04-07T13:47:37Z")
> [@jjakucyk](#):
>
> So to circle back to the OP, it’s not so much a point as it is an intersection of vertical planes. I don’t know if it really changes anything though.
Yeah the whole is a point border is kinda debatable.
What stunned me is this co-worker (a very smart guy) said that a geometric point has length/dimensions. Sure the monument on the ground does, but the coordinates that define that location of the monument is not what gives the monument dimensions.