We've all seen the curve with a arc length and radius that don't work, or aren't tangent to bearings in/out. I typically try to fit best I can, look at field evidence and go from there. What say you? I see this a lot on very old plats.
Pretty much the same.....
Field evidence gets a high priority for sure, but when fitting the curve to it I generally like to hold the radius if I can -- it's the one dimension that has intuitive significance to everyone, layman and professional alike. Next I try to make the curve tangent, but I often have let that go. I usually don't sweat the delta or chord.
Same here, Jim. Although I find I have to let tangency go more and mor and more...
I have a fairly recent plat in front of me with non-tangent curves in the streets, and non-tangent curves on both the front and back of the lots, all with insufficient data, so none of the street centerlines and none of the lot lines can be computed. Not one.
I'd say fall back on asbuilt evidence. Occupation (especially ver old) shows intent, we hope.
I also usually regard the radius as sacred.
There's something almost spiritual about the radius and it's relationship with other elements of the curve.
Going off on a tangent can have advantages however.
Or so I'm told.
Don
Delta is stronger, but I agree. Kind of..lol
If I get a bigger hammer usually I can force it to be tangent. Makes some odd bent or twisted looking curves though.
I like to hold a radius, and I try to keep everything normal.
The only thing I wish folks would do is to label a curve "non-tangent" if that's the way it works out. It's ok, just let people know it's what you meant to do. It can drive you nuts.
> I like to hold a radius, and I try to keep everything normal.
> The only thing I wish folks would do is to label a curve "non-tangent" if that's the way it works out. It's ok, just let people know it's what you meant to do. It can drive you nuts.
JB,
How does this look to ya?
Part of a recent plat of mine.
:good:
Are we going round and round?
When routes were initially being located they used angle points, "PI's", I hold the tangent intersections and then for the PC and PT locations I use the record tangent lengths, compute the tangent curve and compare it with the given radius, if close I hold the PI and Tangent length and let the radius float. I measure the external as a check. Reasoning being that the PI and tangents were located in the field and the radius is seldom measured which makes it a weak link.
jud
Curves that don't work should do the responsible thing and go out and get a job.
They should not be given welfare, food stamps and other free lunch programs.
Oh, sorry, I figgured it was another P&R post.
If their non-tangent curves match their linework (and the field evidence), then just drop the tangency.
Depends. Many of the FM roads in Texas are not monumented at the right-of-way, but the construction plans show many of the culverts with stations. I try to use these to back in the curve and fit to the existing centerline (where possible). Sometimes, the curve is so long, I end up setting the radius based on the delta between structures and then evaluating the curve data from there.
My experience is that no curves before 1980 were built tangent (try as they might) and I end up with nontangent curves to hold the radius. I've only seen a few that I could make ALL parts of the curve work and were tangent.
Now, old railroads, with the rails intact, seem to work better than highways, and I can generally (after understanding that the curve won't fit the rails due to the rails making spirals in and out) make it tangent and make the curve work.
Also, I consider it a win, if the curve data is to the nearest minute and distances to the foot if I can keep it within a minute either way and within a foot either way.
It depends... I try to determine which piece of curve data is inconsistent with the rest. If the radius is an even foot I usually try to hold it, if the tangent distance is an even foot I usually try to hold it, if the degree of curve is an even foot I will try to hold it. It is usually possible to determine the intent, but not always...
I agree Jud on highway plans but many of these curves are on subdivisions etc that never were layed out by those methods. I try and hold radius but there are cases where i will hold arc length. it just depends.
I also would attempt to hold the radius over the other elements of the curve. Judging by the answers produced here it is considered good general practice.