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Curves?
Posted by spledeus on March 21, 2017 at 9:05 pm***************** (expletive deleted)
Curves from the 50’s, 60’s and 70’s can make me angry. I have no problem with 0.01 or 0.05 but 2.0′ on curves with 25′ tangents?
spledeus replied 7 years, 4 months ago 7 Members · 7 Replies 
7 Replies

Is that errors in the length of the curves? Perhaps a long chord instead of an arc? My big problem with “old” curves is not enough data to reproduce.
Andy 
I assume you mean errors of 2.0′?
Here in Oregon, the platting laws are such that you are required to put 5 elements of a curve on a plat. Radius, Delta, Arch Length, Chord Bearing, Chord Distance. Problem is since everyone sees this on plats they think that is what is required on everything, and noone seems to be able to put a radial bearing on a nontangent curve. So the item held… Chord Bearing!!! That is where a lot of times we find the error. Someone couldn’t calculate their way out of a hole, and puts the chord bearing on, then the next guy doesn’t check it, and holds it.
But as Andy says, at least there is enough data on these that we can figure it out… just the problem is to many surveyors in days past have only calculate around a property with B & D from the chord and never check… 


paden cash, post: 419510, member: 20 wrote: Here in Oklahoma curve data on plats use to be optional apparently. With plats like we have, you can pull just about any distance out of your butt and try to make it fit…
That goes for around here as well. I’m dealing with one right now, technically it should be a spiral, but it’s not. Radius at PC on incoming tangent is 25′, but 30′ on the PT outgoing. F’it, used the mean and call it nonradial. I guess if they aren’t going provide any curve data, I’m free to fudge things here and there. The surveyor of record did.
Willy 
I’ve complained before about the 1950’s plats our church is on (straddles two subdivisions by same owner). Usually there is a curve table with enough data you can TRY to check. Some street curves check nicely by arc formulas. One or two check nicely by chord (railroad) formulas. The ones right in front of us don’t check as either. Maybe designed by arc formula and then backcomputed railroad degree of curve? And the lot dimensions don’t add up right, so you can’t work back into the curve design from the surroundings.
. 
I was working on one with tangents, lengths, radii and bad math… some 2 foot busts with 20 to 30 foot tangents…
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