I understand curves well enough, but have never really had to work with railroad plans to become familiar with how they present the info. Nor have I worked much with spirals.
A little history: the RR was first built around 1880 or so. Then, they just went through the local farms and got a deed for 60' wide R-O-W withouth really specifying where it was. Not too long after that they realigned this portion of the railroad.
From about 1895-1930, they were purchasing adjacent lots and portions of lots. The lots were from an 1837 plan of lots, with references to roads, etc that aren't there at all.
At one time there were 4 sets of tracks here, nowadays just one.
I have a 1991 map from the railroad that shows a MBL (monumented base line) with stationing, and a dotted line which I assume is the single track as it exists now. There is a tangent to the SE and a tangent to the NW of the area I am looking at. Actually, I already did the tangent area to the SE, it worked out fine, but later they extended the area of interest. My previous work shows the track to be about 7 feet from the MBL (which of course I cannot recover the monuments, as they are under the ballast). Without getting into details, the government wants (MAYBE) to buy/obtain by whatever means a portion of one side of the railroad property for an access road. They have a crossing in the tangent area I already worked on.
So this new 1991 plan shows the following:
On the dotted line (I assume TA means track alignment?):
PSC 878+97 T.A./100' SP
PCC 880+47 T.A./1°30R DEL16°21'
PCC 889+87 T.A./100' SP
PST 891+37.0 T.A.
Okay, so what I don't understand above is there are 100 foot spirals at either end, but the stationing between the start of the spiral and the PCC is 150', and the stationing at the other between the 2nd PCC and the end of spiral is 150'.
Next the MBL:
PSC 880+74.4/60' spiral
PCC 882+61.4/3°07R DEL16°21"
PCC 885+99.0/60' Spiral
PT 887+86.0
I have an old rr plan that describes 5 parcels (which are the area of interest) being conveyed from the RR to the County for a road (which is the adjoiner, now a state highway). It specifies that the R-O-W is xxx.xx feet (varies) "from T.P. of M.B.L." What is a T.P.? I went to DOT, they don't have R-O-W plans for the road, says the county should still have that. Of course the County says they gave it to the DOT way back when....
So, sounds easy, just find the MBL....which I pretty much have done previously in the adjacent area by finding corners that are called for with distances to the MBL on the plan. But, I need to extend the MBL through this curve section, and the above data is not real clear to me as far as the spiral lengths and stationing.
Any help from a RR expert would be appreciated.
This is my helper when it comes to calculating spiral curves
From my experience with RRs, they do not do easements, they do License for crossing R/Ws. Since you are doing this for DOT, it may help when talking to each side as to what they understand.
Nah, not the DOT, it is the US. They seem to think they can take it one way or the other. It is a strange case, this probably won't happen anyway. Depending on how they do it, they would have to build a massive retaining wall.
There was a landslide closing the road leading to the crossing, which the US has a license for. The road on the other side, between the river and the tracks, leads to a US facility that is critical infrastructure, and has probably 5 to 10 people there 24 hours a day. It also leads to a township park (now closed because of the landslide) and a township maintenance facility of some kind. The US now has a temporary license or permit or something to drive along the tracks for about 600 feet to the crossing. The RR put up a gate and gave the US keys. I never see it closed, though.
The simple solution is to fix the landslide. That helps them, and the town. But there is some animosity between the US and the town. The town is small, and can't afford to fix the landslide themselves, altough it is on their road. The township warned the US that the road was going to fail, but the US ignored them. So they closed it. Then it failed, drainage problems in my opinion. It could have been repaired relatively cheap at first, before the landslide, not anymore. It threatens a nearby road that leads to 10 or 15 houses.
Nice program, thanks for the link. But, looking at their diagram, shouldn't a "100 foot spiral" mean a 100' long spiral (i.e. Lm in their diagram)? The stationing being 150' difference is what throws me. Same thing with the 60' spiral on the MBL.
John I have some experience surveying around railroads, not as much as others here, that leads me to question some of what you have assumed. Terms I have seen used in both highways and railroads would be as follows:
P.C. = Point of Curvature, beginning of circular curve or beginning TANGENT POINT (your TP?)
P.T. = Point of Tangent, end of circular curve or end TANGENT POINT (your TP?)
T.S. = Tangent to Spiral point, where tangent center line ends and spiral begins.
S.C. or P.S.C. = Point of Spiral to Curve, end of spiral beginning of circular curve.
P.C.C. = Point of Compound Curvature, may be any point where radius of circular curve changes.
C.S. or P.C.S. Point of Curve to Spiral, Point where a circular curve ends and an exit spiral begins.
S.T. or P.S.T. Point of Spiral to Tangent, end of exit spiral and highest numeric station in a compound spiral/curve combination.
Given the above I would expect what you have posted to have additional entries similar to those shown in bold:
PTS 877+97 Begin 100' Entry Spiral
PSC 878+97 T.A./ End 100' Spiral Begin ?°R DEL ??° 150' Curve
PCC 880+47 T.A./1°30R DEL16°21'
PCC 889+87 T.A./ Begin ?°R DEL ??° 150' Curve
PCS 890+37 End curve Begin 100' Exit Spiral
PST 891+37.0 T.A.
The total deflection of the entry and exit tangent lines will be equal to the central angle (DEL or Delta) of the circular curve(s) and the deflection (? THETA) angles of both spirals. Check the bearings of the tangents and the totals of the data you have. The entry and exit spirals would normally be equal (mirror image) having the same amount of (? angle) deflection. There is likely just enough data on the plans to derive the needed values. Also don't forget "Searles Spiral - A surveying technique used by railroad surveyors in the the late 1800s and early 1900s whereby they approximate a spiral by use of multiple curved segments." I have seen up to three 100 foot long circular curves leading into and exiting a longer (1 mile) circular curve.
John Lm in the diagram is the length of the circular curve. Ls would be the length of spiral and Ts the length of the tangents from the ST to the PI or PI to the TS.
You need to talk to Charlie Tucker.
The RR's are highly regulated for a long time. The ICC required some maps be made. These are all on record with the government. Besides all the deeds from the local records you can get:
DV-107 Land Schedule
ICC Field Notes (sort of an alignment by station topo)
ICC Valuation Maps (The Val Map)
These would probably help you sort out the evidence and figure out where the CL of the ROW is.
John,
Try Nick Remy of PA-PLS. There was a seminar given in the eastern part of PA on railroad surveying. The presenter, if memory serves me well, did work in the Philadelphia area on RR realignments. Maybe Nick can give you his contact info. Try to get the "custodians" records that go with the VAL maps if you can. The custodians records are the key to the numbered parcels on the val maps. They usually have the parcel owners names, the type of real estate interest conveyed, the deed book and page numbers for the taking, acreage and other incidental information. Spirals were usually used for rails while the ROW was usually done with simple curves. Of even more help would be the construction plans, but I have never been able to get these from any railroad.
Sorry I can not offer more than that as I am in Leverett, MA visiting the grand kids until Saturday.
Al
Dallas: thanks. Much of what you are saying makes sense with what I have, slthough not all (that would be too easy!).
I find it strange that a "Monumented Base Line" has spirals.