I have a project where one of the deliverables is cross section data (tabular) at 25' intervals for a 2900' section of highway (one side only, two eastbound lanes). We scanned it, so I just need to cut the sections out of the point cloud. It is tangent-curve-tangent. But, there is a station equation at the PC, with a change of about 5.8 feet. How is this typically handled? I have a request in to the end client, but just wondering what others do.
I would usually put sections at even 25'. This project was a bit difficult because the highway is the original 1949 section (most other parts have been widened, with monuments placed). This section has no monuments, so all I have to go off of is the 1949 plans. The only things on there that I can use are two overhead bridges with data on the plans, one on a curve and one on a tangent (which is skewed to the C/L of the road). It does have a C/L median barrier, which is where the alignment line goes (no spiral). Interestingly the catch basins in the median are all on 200 foot spacings (if there is one). Since the median barrier was not there originally, I have to assume that the CB's were rebuilt, one on either side of the median barrier. My client located all four corners of all of the CB's, plus the inverts. But the stationing on these varies å± a foot or so, so not real useful for trying to recreate the original alignment and stationing. They had to shut down a lane to get these as there is no real shoulder. It matches our scan data extremely close, not even perceptible.
For topographic mapping I would just give a cross section every 25 feet since it is the density that is more critical that the actual stationing for this type of mapping. We normally specify that we will collect data on a nominal 25' cross section so I'm not tied to a specific station and I have a little wiggle room on the spacing. Our DTM would then be produced and supplied to the client. Given the fact that you are cutting cross sections out of your scan data I would suggest cutting them on even 25' stations and curve points making sure the actual distance between any two cross sections is more that 25'. That is how I would handle the mapping if I was requested to provide cross sections. Similar to design plan sets.
Sounds like there should be PennDOH (Department of Highways) construction plans. I did a survey of a farm parcel a few years ago based on 1927 PennDOH plans. The plans called for station ties to iron pins and ties to dwellings. I found one of three 1" iron pins in concrete at a P.I. (it was 1 of 2 perpendicular offsets), 2 ties for a station, 1 to a 1" iron pin in concrete and one to a P.Q. house corner, at about a 1/2 mile away I located porch and front house corners, it was the porch that was centerline station ties. I held them like gold and the tangent along the sideline was also the first course of my new description. The iron pins were well buried and had nothing to do with property corners and were thankfully not near any construction since 1927. I have used inlets multiple times to get on highway stationing, and used it them to lay in record curves. I have also used culverts and bridges to get on RR stationing.
Paul in PA
Not a PennDOT highway, it is PTC. They gave me the only plans they had, which were the original 1949 design plans. The only thing on the plans with real stationing were the overhead bridges. None of the inlets had stationing, although they are shown on the plans at even stations (at least in the medians). This section has been repaved, and a barrier installed, but not rebuilt, so they don't have anything newer. Two nearby sections (30 miles away) we scanned were totally rebuilt and realigned (major realignment) in 2010 and so we had newer plans with monuments, everything on project grid (modified SPC, all coordinates multiplied by a combined scale factor, which I am against in concept). That was of course much easier, except it has spirals. We only scanned the EB side, but they want the alignment and all ROW on the drawings.
John Hamilton, post: 407608, member: 640 wrote: Not a PennDOT highway, it is PTC. They gave me the only plans they had, which were the original 1949 design plans. The only thing on the plans with real stationing were the overhead bridges. None of the inlets had stationing, although they are shown on the plans at even stations (at least in the medians). This section has been repaved, and a barrier installed, but not rebuilt, so they don't have anything newer. Two nearby sections (30 miles away) we scanned were totally rebuilt and realigned (major realignment) in 2010 and so we had newer plans with monuments, everything on project grid (modified SPC, all coordinates multiplied by a combined scale factor, which I am against in concept). That was of course much easier, except it has spirals. We only scanned the EB side, but they want the alignment and all ROW on the drawings.
Did you get the Charlie Miller Reference notes?
It seems that someone named Charlie Miller had to go back and reference alot of the Turnpike. We could find very few of the references that show up on the original plans, but when we got the Charlie Miller notes most of his references are still there.
What section are you working on?
I did get two pages called "miller references FB 3-007" (pdf). I did not realize what they were, very basic sketch on each page, but now that you mention it I do see some IP's, looks like in the C/L (which would be under the median barrier), but some IP's on 90's as references, including a set of 4 at the PC. These notes are dated 1979. This is a section around MP 234. The other two sections are on the recently realigned section exiting the Blue Mountain tunnel (eastern tunnel of the back-to-back tunnels). Our scan starts at the tunnel portal and goes for 450', then starts again 0.5 miles east and goes for 0.6 miles, three sections in all, 5500 feet total. We had to do the scanning in the week before their holiday "shutdown" (where no work is allowed during holiday peak travel times). We had to do the "quadruple" scan mode so that we could get shots on almost everything despite the traffic.
Interesting thing was I got on at New Stanton, went out to look at all three sites (my crew was out there scanning), and did U-turns at the exits just before the toll plazas, and also at the tunnel where there is a crossover above the portal. I then went back and exited at New Stanton 6 hours later. So, I entered and exited at the same place. I checked my ezpass account and they charged me a flat $5.00.
I may have a little bit of "fill-in" scanning to do, I will look for those miller references then, if not I will check on the way to or from Hershey later this month. We looked for all of the new rebars and references and benchmarks set for the new section (about 25 points), and only found one, a reference for the EB baseline at the portal, all the others had been wiped out by construction. We did find most of the concrete mons that I bluebooked in the late 90's (set and surveyed by others), all of the control was based on those mons.
