I disagree - Chord Bearings can be the best information.
People don't make a non-tangent curve because they use a chord bearing. There is usually some other reason. But if you have the CB, then it doesn't matter if it's tangent or not.
Wattles used radial bearings - that's good enough for me!
Chord length and bearing are the most directly relatable data to what is on the ground, and therefore most important. The main information you really use in a retracement is the chord.
You don't measure radius (or equivalently degree of curve) and length for a typical curve. Nor do you use any of the other parameters for anything but a calculation check unless you are staking points on the curve, such as for the street C/L and curb.
With today's pathetic excuse for a business model you are correct. Back when a party chief computed and checked his own work and set pins in subdivisions using a plat we needed complete curve data...
:good: :good:
I don't have a problem with using chord bearing or the radial bearing (I use chord bearing but just as a matter of habit), but I say always state the direction of concavity. (if that's a word). The chord bearing and distance will work perfectly regardless of the direction of the curve. Radial bearing, by definition, is the bearing from the radius point out, but not everyone thinks of it that way and sometimes it is hard to tell on a sketch especially if it's a 6,000 foot radius and a 175-foot arc length.
> I think the reliance on cad is a big factor in this problem. "Just click on it", mentality. Oregon requires chord bearing and chord distance along with radius, length and delta on plats. I like the idea of chord bearing and chord distance because you can always compute the curve along with radius and legnth, but it does result in a lot of broken back curves because one does not have to be so cautious about computing concentric curves, where as in California we typically computed through the radius with radial bearings where needed, which was ok until someone busted the radial. My 2 cents, Jp
That is exactly why I despise Chord bearings.
If a curve is tangent, it is usually not labeled tangent. If the chord bearing and distance are provided, then that is now a platted (original) value and must be weighted as a plat bearing and distance. No where on the plat does it say "Tangent Curve" so it is implied. In court which is going to win, an original value shown on the plat, or an implied tangent curve? I have a feeling if it came down to it the chord bearing and distance, and all the broken back curves would hold.
The probable answer as to the winner would be 'which one matches the monuments', followed immediately by, 'which one makes it close'...
I've seen that, too. I think "delta, radius, and arc" are the default settings on a LDD CAD curve table.
What irks me is that Florida MTS actually does codify that as an option, which is probably why a few surveyors who don't use their heads thinks it's okay in all situation. I which the Florida BOR would delete or clarify that line.
(2) Boundary Survey, Map, and Report:
(a) Boundaries of Real Property:
....
5. Curved lines with circular curves shall show the radii, arc distances and central angles, or radii, arc distances, chord distances and chord bearings.
At LSU, I teach my Civil Engineering Juniors to post EVERYTHING for every curve. The future Land Surveyors in class do take note.
If I am reconstructing an alignment I will always use a tangent curve (unless specified otherwise) using the delta and radius. If chord bearing and distance is supplied I will use it as a check. If things are close enough I hold my tangent curve. If I was to use the chord bearing and distance for the tangent curve...my curve 'can' become non tangent...albeit slightly, which is why I don't use them when recreating centerlines.
On my maps I will put all the curve information because it's there and easy to show.
When describing curves in a legal I will only use the direction (left, right)radius, arc length and delta...unless indicated otherwise by the reviewing agency. I always indicate tangency in the legal for clarification.
For non tangent curves in a legal I will use the chord brg and distance along with the information above.
I was taught to assume tangency unless otherwise noted and that's stuck with me.
almost forgot...seems WA likes to have the radial bearing shown on maps and in legals. I am constantly amazed at how many radial bearings that are completely backwards...and not FROM the center.
I'm with you two.
The curve data shown on any plan is there so you can calculate the bearing and distance between the end points of the curve. Without that bearing and distance you may never get the boundary to close.
> > ... There are only the usual three curve elements (delta, radius, arc)....
> In each of the 3 states I'm registered in the required curve elements are specified in the statutes. It's not a matter of personal preference.
>
> The radial bearing thing works fine. In fact that is what is required in British Columbia. It is actually easier to annotate on a map. But OR, WA, and OK law requires that chord bearings and distances be given.
I Know about OK. It is ridiculous. A radial bearing is much more accurate way to mathematically build a curve from the data.B-)