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How is centerline, and stationing defined?
aliquot replied 3 years, 3 months ago 24 Members · 51 Replies
If it’s a DOT highway, calculate an average bearing for the centerline tangents each side of the curve based upon the R.O.W. mons, then fillet with the record degree of curvature. The PC and PT monuments only establish the bearings on the tangents, the calculated PC and PT will slide up and down the tangents.
- Posted by: @scrim
If it’s a DOT highway, calculate an average bearing for the centerline tangents each side of the curve based upon the R.O.W. mons, then fillet with the record degree of curvature. The PC and PT monuments only establish the bearings on the tangents, the calculated PC and PT will slide up and down the tangents.
That’s all well and good right until the mons get ripped out during rehab and new ones are set by second-rate contractors, maintenance crews and/or engineering departments without any regard for precise location. Or they never get replaced at all.
It doesn’t take much error in those CL mons to start seeing ROW lines, especially through those filleted curves, that significantly disagree with the original ROW as monumented, not to mention long-established occupation lines, meaning you’re now open to litigation from landowners along the ROW. Utilities running just inside the actual ROW may now be shown on private land, which can cause even more headaches.
I don’t mind centerline mons (although I dislike having to dodge traffic to pick them up), but they absolutely must be tied to a maintained control network existing outside of the right-of-way itself, so that they can be re-established precisely. There are precious few highway and public works departments (not to mention licensed surveyors) that both understand that and conduct projects accordingly.
“…people will come to love their oppression, to adore the technologies that undo their capacities to think.” -Neil Postman Until you have to tie one in a busy roadway.
@john-putnam Or stand there with a hammer drill to set and epoxy them in. Not sure which is worse.
In a great many cases – particularly with plats and road alignments created in the last 30 years or so – the math fits the (undisturbed) monuments close enough that the differences are not significant. Centerline monuments, being installed in the asphalt or in monument cases are most likely to be undisturbed. Any deviation of individual monuments outside of the travelled way can be attributed to disturbance.
So … this may be heresy to some … It seems to me that there is little to be gained in fiddling with the math, thereby clouding the record … just to put the point that already falls on the cap right on the dimple.
If that is not the case – if the monumentation isn’t matching the math by a large swing – I’m going to seek to hold the tangents as monumented, the tangency of the curves, and the radii.
- Posted by: @nate-the-surveyor
Do we shoot centerline, and make all curves tangent?
Or, shoot r/w markers, and use Hwy dpmt radius, holding the r/w markers, even though this makes broken back curves, and odd road widths?
Or, a combination of these, making the curves properly, and just figure that the whole shootin match was not that accurate in the first place, so we modify the curve data, to make it pretty close, and tangent?
What is the right answer?
Thank you,
N
yes, yes, yes and all of the above.
You’re welcome
In my experience, Alaska DOT&PF will back down when faced with a strongly opinionated surveyor or land owner that insists that they abide by their own monuments.
This issue comes up over and over again and those that favor the math over the monuments have never been able to provide any justification besides, “that was the way I was tought”, or “that is how DOT told me to do it.”
I don’t get the, “but they were set by contractors” argument. Courts do not generally reject monuments becasue they were not set by surveyors. Don’t forget that more than half the original PLSS monuments were set by contract laborers picked up locally.
@jim-in-az
The invisible centerline is pushed by DOT in many states. Of course we as professionals know better then to do something just becasue a goverment agency wants it that way. For years I have been waiting for someone to come up with something authoritative to translate DOT’s wish into law.
- Posted by: @john-putnam
I would need a real good reason to create one were it not called for.
Monuments set under the direction of DOT and relied on by land owners?
There are some areas in my area where the monuments were set from center line using a 90 prism or clapped 90. The distances are very tight as they were carefully chained. Soon after the center planting was done and only the r-o-w mons remained. I’ve retraced many of these.
As some have said the process of recovering the r-o-w established this way is simple. Recreate the tangents and fillet at the proper degree of curve. The monuments fall on the r-o-w but usually miss the station. This method will preserve the location through the curve nuch better than a non-tangent curve. It honors the way the monuments were set.
If you apply this method and it disrupts long-standing occupation you have more work to do. I would encourage you to work through evidence based methods rather than trying things until it appears to fit. Accidentally getting an apparently correct answer without evidence to support it will eventually end poorly…
Highway right of way monuments in Oklahoma are generally only very crudely positioned. Paden has written of how, in the past, they were set by fencing contractors working from half-hearted survey crew guidance. If they fall within single digit feet of the theoretical you are doing well. If nothing else is available hold the mons for tangents, develop a centerline between them, hold the tangency, hold the radii, hold the right of way width. The land is cheap enough that nobody is going to get real exited about a few feet of prairie.
@mark-mayer
We have areas like that as well. Depending on the method of creation the width may yield to the monuments. A lot of guys flip out when you do that…
- Posted by: @nate-the-surveyor
Or, shoot r/w markers, and use Hwy dpmt radius, holding the r/w markers, even though this makes broken back curves, and odd road widths?
I’ve always been told R/W markers, formerly known as “mower’s markers”, weren’t set with any high degree of accuracy. The only ones I’ve ever shot were along Florida’s Tpk. in Palm Beach County for an FDOT R/W survey. They had SRD scribed in the side facing the Tpk. along with an “X” scribed in the top.
MH It is certainly true that many ROW monuments where set by very imprecise methods, but since when has inpresision been a reason to reject “first” monuments?
- Posted by: @nate-the-surveyor
Do we shoot centerline, and make all curves tangent?
Is it a requirement that all highway curves should be tangent? Maybe a highway engineer’s safety requirement? What’s the purpose of the survey? Topo or design? No way I would shoot the centerline of Florida’s Tpk. back in 1994. I suppose that would be doable nowadays with a scanner? On that same survey the boss had me locate the edge of pavement. That was not clearly defined because of overpour. I think I wound up shooting the white stripe along the shoulder. Anyway, great question!
MH IMO, the assumption is that curves are tangent unless they clearly and positively aren’t. Remembering that highway curves often have spirals in and out.
The design centerlines of course have to be tangent. It is no fun driving around non tangent curves. But there is no particular reason the right of way curves have to be tangent.
@mark-mayer
High speed highways often are designed with spiral curves, but spiral ROWs are less common.
spiral ROWs are an abomination.
Hopefully the complaints and discussions to the DOT removed them from future design.
However, the guy that was on board with putting a stop to it retired.
It’s remarkable how little the mid-point of a curve will differ between a typical spiral-curve-spiral and a simple curve.
I’m putting together a property line against an interstate highway, the right of way was designed in the 1950’s, simple curves, nearest minute bearings, curves all designed using degree of curve, jogs at even stations, PCs, PTs or property/section lines, frankly a pleasure to work with.
Then nearby is a state highway designed in the early 2000’s: ROW spiral-curve-spiral, jogs 15-30′ beyond the TS or before the ST, very messy.
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