Not too sure?
Nobody tried surveying???
😆
For curves I want to know four things: radius of the curve, arc length, chord length and chord bearing. They do not tell you if the length provided is the chord length or the arc length. On a large radius the two numbers are very similar but a few hundredths here and there add up over a long route survey.
I've seen too many with HUGE radii and a relatively short length where it is next to impossible to tell if it's an angle to the left or the right. It would help if the curve data was ALWAYS given on the inside of the curve, but, that's seems to be asking too much. That is where having both chord bearing and distance is quite helpful.
Yeah... unless it's potentially a non-tangent curve. That's why I like chord data, it covers all the types of curves. I mostly like chord data because it lets me quickly draw a boundary without having to change out of the BD tool.
Except the chord distance is rounded, typically to the hundredth. The radius is typically an even number, exactly, say 400' and the Delta is to the arc second. My experience is that if I construct the ends of a curve using a chord bearing and distance, the computed radius and delta will not be the exact numbers (or proper second) they are intended to be, so I have always gone through the radius point, going 400.00 feet (in my example and assuming a tangent curve or where a radial bearing is given for non-tangent), use the labeled delta (left or right) then then back the 400.00 to the EC. The integrity of the numbers remain intact that way.
Guess I'm an old hand, degree of curve was always the standard for design. Of course I long ago stopped laying out curves on line, still habits die hard.
Well, if the delta was the given dimension then that's what I would use too. If all you have is the arc length, radius and chord data though then who's to say what the delta is intended to be? But I think you are right about the chord length being the weak link. The end of the arc rarely lands on the end of the chord but at least the bearing is maintained. Hopefully that is enough to build an accurate curve.
@spmpls P.S. The map example for this thread came out of your former agency. Not casting any blame, mind you -- everyone makes mistakes!
Surely done after I departed, likely under contract to get all of the SSJDD parcels digitally mapped. I am sure that parcel number is a "levee" parcel number and not for the State Water Project.
I want the delta and the radius. Interesting to see what people prefer.
I prefer the delta because it tends to give the correct (same as shown) out bearing on a tangent curve when I use CAD to calc it.
If provided the arc length you can back into the delta. We encounter so many non-tangent curves it is handy to have the chord data to confirm the intent. People screwup left and right so often it is amazing.
I grew up in a world where almost everyone can identify cardinal directions in a flash and know left from right. My high IQ daughter still has to form an L with her left thumb and pointer finger to remember that is her left hand. Tell her to go east or west and she'll get that right every time.
Chord bearing and length would be great.
Around here, it is delta, length, radius, and (if you are lucky) a radial bearing IF the curve is non-tangent. I cannot remember seeing anything else on a plat or legal description. Of course, all of the data can be derived (backed in) given adequate information. I wouldn't mind chord bearing and length.
For the most part, however, the arc length is the last thing I use in actually calculating curve.
My experience is that if I construct the ends of a curve using a chord bearing and distance, the computed radius and delta will not be the exact numbers (or proper second) they are intended to be, so I have always gone through the radius point, going 400.00 feet (in my example and assuming a tangent curve or where a radial bearing is given for non-tangent), use the labeled delta (left or right) then then back the 400.00 to the EC. The integrity of the numbers remain intact that way.
That's the way I handle curve data - I will use chord information as a check, but nothing more, if I have supplementary data. Draw the entry/exit tangents and fillet with the record radius, check the delta and arc length first before looking at chord info.
Nowadays I label the radial bearings at all curve PC/PTs on my plats, even if the curve is tangent. Gives the next guy a check on tangency, and an easy way to calculate/check the radius point.
My preferred method has become creating the two tangent lines and using the fillet command with the radius. I then can check the curve information. The question is always where to put the rounding on calcs in CAD.
They should make this website a requirement for the degree seeking students that need to experience the many and more or less correct ways you can lay out curves etc.
Man I love this site!
NC requires chord bearing and distance so I add it below R and L. In the Boone, NC area it seemed as though PLSs discovered horizontal curves in the 60s and 70s.
Like most people, I'm drawn to symmetry like a moth to flame, but other than aesthetics, I don't see that tangent (or non-tangent) curves are a great improvement in many cases. There's beauty in simplicity.
Do you get physically ill when reviewing plans that have bizarre non symmetrical compound curves and convergent giant radius almost straight lines??
Just wondering (twitch....twitch...) 😎 😎 😎
As professionals it's helpful to have discussions with designers about some of these issues.
I believe it's been helpful when I have sat down with them.
The No.1 issue I've brought up is spirals in the ROW.
Then it's the jogs in and out slightly after a direction change. One of the designs from the early 2000's had numerous jogs before or after a TS or SC. The highway needs to flare out for cut/fill, culvert, drainage purposes but why do it 10' up station from a TS. For a 30' jog that's 300 sq ft. and even at $10,000 an acre that isn't $100. Way more than that is spent buying a $100 concrete ROW monument, installing it, writing the description, calculations, ect.
I think it's helped, no more spiral ROW curves and legals, no more jogs slightly before or after direction changes and hopefully no more 1/4 degree curves, I think it's safe to say that a 1 degree curve covers almost all situations.
It's a matter of cleaning up a ROW as much as possible and making them as clean as possible. Of course, there are times a ROW has to get very complicated, when it's up against senior lines and such. But out in the middle of ranch lands with no homes or development......that's a time for a simple design.
@jitterboogie lines that are seconds from being -//- And center lines with minor deflections for tenths over hundreds of feet...twitch twitch
Mules always used short chords for road design. Following in their footsteps is a challenging task at times.
