I am currently surveying a parcel, and running into something that I have seen a handful of times:
The rural route whose right-of-way comprises roughly 1/4 of the exterior boundary has a mathematically defined centerline, that only "mostly" matches the road as it exists in the field. The road is in a curve at each end of the property and tangent about 2/3 of the length of the east side. The tangent section is pretty much the correct length, and both curves look pretty good by themselves, but when I hold the tangent and the northern curve, the souther curve is out about 1.5' from centerline in places. When I hold the southern curve and the tangent, the northern curve is out about 2' in places.
What do you usually do in this situation? Split the difference between the two curves, or hold one as good? I'm inclined to split the difference. I also plan on locating some additional back tangent to see if that clears anything up - I suspect it will, as the curves have probably slowly "walked" with re-pavings through the years. There is no ahead tangent, the northern end is the limit of the road project.
I'm used to things matching really well, or not at all when it comes to route surveying. You can lose a lot of hours quickly playing around with these "tweener" scenarios.
What created the defined centerline?
Was it title survey that found its way into a deed description?
Did the County dedicate the road by the description?
For rural road, 1ft to 2ft off actual centerline is close enough in my books because most of the time a survey is to locate something that changes every time the road is rebuilt and/or graded and ditches cleaned out.
There are a few defined county roads in this area that once were County and/or State Highways that were turned over to the county.
They were purchased and surveyed and they fit on the ground as designed and described in deeds.
Most county roads have gone thru rerouting by maintenance over long periods of time.
IMVHO, the movement of a rural roadway driving lanes by naintenance does not move a boundary line. If that were so, people would be moving them on purpose as they have in the past in attempt to cut access off to other owners and to gain use of land.
0.02
A Harris, post: 343658, member: 81 wrote: movement of a rural roadway driving lanes by maintenance does not move a boundary line
:good:
Agreed for sure, that's why I'm going to locate more back tangent, because the tangent sections should be pretty much the same as always. The right-of-way was created by a conveyance by deed, and described well in the deed. I have the highway plans for simplification, they match the deed well. Even when there's an occasion to say 1-2' is close enough (and I agree that it is), I like to have a documented reason as to how/why I settled on the location that I did.
A Harris, post: 343658, member: 81 wrote: What created the defined centerline?
Was it title survey that found its way into a deed description?
Did the County dedicate the road by the description?For rural road, 1ft to 2ft off actual centerline is close enough in my books because most of the time a survey is to locate something that changes every time the road is rebuilt and/or graded and ditches cleaned out.
There are a few defined county roads in this area that once were County and/or State Highways that were turned over to the county.
They were purchased and surveyed and they fit on the ground as designed and described in deeds.Most county roads have gone thru rerouting by maintenance over long periods of time.
IMVHO, the movement of a rural roadway driving lanes by naintenance does not move a boundary line. If that were so, people would be moving them on purpose as they have in the past in attempt to cut access off to other owners and to gain use of land.0.02
I meant for the above comment to be a reply to your post. Not sure what happened.
Plumb Bill, post: 343652, member: 226 wrote: I am currently surveying a parcel, and running into something that I have seen a handful of times:
The rural route whose right-of-way comprises roughly 1/4 of the exterior boundary has a mathematically defined centerline, that only "mostly" matches the road as it exists in the field. The road is in a curve at each end of the property and tangent about 2/3 of the length of the east side. The tangent section is pretty much the correct length, and both curves look pretty good by themselves, but when I hold the tangent and the northern curve, the souther curve is out about 1.5' from centerline in places. When I hold the southern curve and the tangent, the northern curve is out about 2' in places.
What do you usually do in this situation? Split the difference between the two curves, or hold one as good? I'm inclined to split the difference. I also plan on locating some additional back tangent to see if that clears anything up - I suspect it will, as the curves have probably slowly "walked" with re-pavings through the years. There is no ahead tangent, the northern end is the limit of the road project.
I'm used to things matching really well, or not at all when it comes to route surveying. You can lose a lot of hours quickly playing around with these "tweener" scenarios.
I'd decide what really controls the location of the boundary - the centerline of the roadway, the road right of way, or the "mathematical" locations. In my experience, the math is usually "close", but usually doesn't control anyway.
I have found that nearly all road alignments start off being constructed with tangents and simple curves. Over time, they end up being more of a spiral curve. Because of this, when fitting record geometry to an existing roadway alignment, I do not mind seeing a little discrepancy near the BC / EC.
In truth, we should be building roads with spiral curves instead of simple curves.
imaudigger, post: 343787, member: 7286 wrote: we should be building roads with spiral curves instead of simple curves.
And those will fit within a ROW defined by a simple curve, although not precisely centered.
Within a monumented ROW
Around here many of the older plats started life as logging roads or railroads. A surveyor or engineer as-built them and fit curves and tangents as they saw fit to establish boundaries. I don't stress about where current pavement is unless the geometry doesn't work for some reason. Actual location of improvements is pretty far down the list of determining factors in my decision process in many places.
imaudigger, post: 343787, member: 7286 wrote: I have found that nearly all road alignments start off being constructed with tangents and simple curves. Over time, they end up being more of a spiral curve. Because of this, when fitting record geometry to an existing roadway alignment, I do not mind seeing a little discrepancy near the BC / EC.
In truth, we should be building roads with spiral curves instead of simple curves.
This is a surveyors board not an engineerÛªs board. I canÛªt believe you posted "In truth, we should be building roads with spiral curves instead of simple curves". I once staked a couple of miles of a large concrete boxed channel that was designed with spiral curves. That was even more absurd than roads with spirals (other than rail roads). Especially when the R/W's include the spiral alignment. My 2 cents, Jp
Should be in meters as well....
I have never designed or staked a job with spiral curves, but, it ends up being spiral after 25 years and it drives better that way as well. Why not start out that way? In metro areas, it is not un-common to see cars running 80-90 mph on the freeway. Spiral curves are now included in the AASHTO Green Book and have been shown to be safer if guidelines are followed.
I sure wouldn't want to have to hand calculate things in the field...but that is unnecessary anyway if you come prepared.
For the record, I would probably kick and scream if I had to work on a road project with spiral curves...especially if there were structures that were designed with spiral curves. I hear ya.
