Determining my Chor...
 
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Determining my Chord bearing and distance

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BStrand
(@bstrand)
1,000+ posts Member

@david-baalman

Exactly, so how can that also be the measure of the angle between the pins the OP has highlighted?

There are the 3 elements of an arc, if you change one then at least one of the others has to change.  The plat information describes an arc 192.22 feet long, but we're interested in an arc 158.68 feet long.  If we want to keep the same radius on the shorter curve then the delta has to shrink, or if we want to keep the same delta then the radius has to shrink.

And this is where the ultimate solution to the problem lies I think.  I'm pretty rusty on this but I think since pi is involved and is a ratio then it's possible to use proportioning to get the answer.  I'll fiddle with it after dinner and see.  If some other math guru has the answer then feel free to throw it out there.

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Posted : May 24, 2022 7:03 pm
David Baalman
(@david-baalman)
100+ posts Member

@bstrand simple they gave the delta only on the overall curve and the arc lengths of the individual segments for each arc, but not the deltas for them. Chord distance is the number I gave in the original reply, delta is as computed above as well.

I think we can all agree that the chord bearing is a lost cause without additional info, and on a more soap-boxy note, whoever drew and stamped this plat, short plat, partition plat or whatever it is gave little to no thought about someone having to retrace it in the future, unless there is significant information shown elsewhere on it that we can’t see in this screen grab. 

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Posted : May 24, 2022 7:09 pm
BStrand
(@bstrand)
1,000+ posts Member

@david-baalman

OK, so maybe this will demonstrate the point.  Take the delta you calculated for the 158.68 foot curve, calculate the delta for the 33.54 foot curve and add them together.  Do you get 183°33'30" like the plat says you should?  I will eat my work boots if you do. 

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Posted : May 24, 2022 7:28 pm

holy cow
(@holy-cow)
10,000+ posts Member

DUEL  At sunrise.  EDM's.  No seconds allowed.  At thirty paces each. The first to drive a nail, set up perfectly over the center of it and level perfectly while drinking a two-liter of root beer wins

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Posted : May 24, 2022 7:49 pm
Brad Ott liked
David Baalman
(@david-baalman)
100+ posts Member

@bstrand Within 6 arc seconds yes. 33.54' arc length at 60' radius is a delta of 32d01'42". 158.68' arc length at 60' radius is 151d31'42". Add those up you get 183d33'24", so within 6" of 183d33'30" shown on the plat. With arc length given only to 0.01' that is all just rounding error. 

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Posted : May 24, 2022 8:06 pm
David Baalman
(@david-baalman)
100+ posts Member

@holy-cow Hell no! If we are dueling I'm using my chaining grips & plumb bob!!

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Posted : May 24, 2022 8:07 pm

BStrand
(@bstrand)
1,000+ posts Member

@holy-cow

They have these contests at the conference each year and from what I hear it's always won by the guy that gets lucky and sticks the tripod almost level on the initial flop.  😆 

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Posted : May 24, 2022 8:58 pm
RPlumb314
(@rplumb314)
200+ posts Member

Late to the party here, but perhaps the OP or others are still subscribed.

The drawing looks like a plat prepared for recording, but it has a sort of watermark reading "UNOFFICIAL COPY." There may well be an official copy out there with more information.

There's a heavy line, with easements on both sides of it, that looks like the line between Lots 3 and 4. But there's no bearing or distance on it. In any jurisdiction where plats are checked, that information would have been added before recording. There might also be chord bearings here and there.

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Posted : July 4, 2022 9:37 am
MathTeacher
(@mathteacher)
1,000+ posts Member

Note that 158.84 + 33.54 = 192.22. 158.84 is not the length of the curve although it's labeled as if it is.

So, we're dealing with a curve with delta = 183 33 30, R = 60, and L = 192.22.

This post was modified 1 month ago by MathTeacher
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Posted : July 4, 2022 1:57 pm

Dave Karoly
(@dave-karoly)
10,000+ posts Member

There are lines missing bearing & distance and some of the arc lengths are unclear from where to where?

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Posted : July 4, 2022 3:46 pm
Nate The Surveyor
(@nate-the-surveyor)
10,000+ posts Member

If you enter all the brgs and distances, you can get a coord for both ends of that curve. Now we can calc in the rp, via dd int. And compare. It'll have the cumulative rounding error, but it will get us close enough, to go to the field...and get observations, and come up with something that would make a hand grenade smile!

N

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Posted : July 4, 2022 5:09 pm
RPlumb314
(@rplumb314)
200+ posts Member

On the south line there is a non-tangent curve with nothing to indicate its orientation. It might be tangent to some line that is outside of this drawing.

Bearing and distance are missing on the line between Lots 3 and 4 (marked below), plus there's a watermark saying "UNOFFICIAL COPY." Both those things suggest that this is not a final plat.

If the OP could come up with a final plat with complete geometry, there might well be enough information to compute the chord bearing he's looking for.

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Posted : July 4, 2022 5:26 pm

Nate The Surveyor
(@nate-the-surveyor)
10,000+ posts Member
Posted by: @rplumb314

On the south line there is a non-tangent curve with nothing to indicate its orientation.

You are right. Multiple non tan curves are only good for.... Hmmmm dunno!

 

N

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Posted : July 4, 2022 8:26 pm
MathTeacher
(@mathteacher)
1,000+ posts Member

The delta for a diameter is 180°, the given delta of 183°33'30" is nearly a diameter and it's West of the center of the circle, not the typical curve diagram in textbooks. I get 119.94' as its length.

Complete the triangle from the SW tangent point to the NE corner (see diagram). In the low resolution of the map, it appears to go through the mark on the curve that shows the intersection of the easement and the curve. If that's true, then the angle of the constructed triangle at its SW point is 48.0234°.

The law of sines can be applied to find the azimuth of the chord.

Based on a big assumption that has to be verified in the field.

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Posted : July 5, 2022 6:37 am
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