It has been a challenge getting any information from the Union Pacific Railroad's real estate or map department. My messages have gone unreturned. I assume they are laying low in response to the coronavirus pandemic.
My challenge is that my vesting deed for a tract just south of their right-of-way doesn't close and the geometry doesn't seem to fit the facts on the ground. My north boundary line is calling to be 50 feet from and parallel to the right-of-way centerline, which makes sense because the r.o.w. is 100 feet through this section. The dilapidated right-of-way fence along the curve is within a few hundredths of being exactly 50 feet from the centerline and has a radius of 4299.14 as measured, but when I trek west into the tangent, it veers 64' south because of topography and becomes more of a fence of convenience than a right-of-way fence.
I was reviewing the Texas General Land office website and they actually have a map with the geometry on it. The GLO is also closed for an undetermined amount time, so there is nobody in their office to scan it or ship it to me. It seems like there are two lines at the beginning of the curve, 25204+13.2 PS and 25203+68.2 PC with 3?ø35' chords and Delta 1?ø00' in between. I'm guessing PS is point of spiral? I'm definitely guessing on the stationing.?ÿ
Looks like at the western end of the curve it says 25232+83.4 PC and 25234+33.4 P.T. with 3?ø50' chords and Delta=1?ø00' between.
https://s3.glo.texas.gov/ncu/SCANDOCS/archives_webfiles/arcmaps/ZoomWork/6/4/6467 4"> https://s3.glo.texas.gov/glo/history/archives/map-store/zoomer.cfm?z=https://s3.glo.texas.gov/ncu/SCANDOCS/archives_webfiles/arcmaps/ZoomWork/6/4/64674
If anyone wants to donate a second set of eyes. Anyone else seeing something different? Also, is there a good spiral curve calculator or information on how to calculate that curve based on that data. I've never dealt with spirals (assuming that's what I'm seeing) New territory here for me.
Cadd can be your friend right about now. If there is enough data to generate tangents both sides of the spiral-curve-spiral you are in business. You can run dozens of scenarios in under an hour. However...
There are as many texts on railroads as there are spur lines. Read up a bit on spirals before wasting time on the math. The dats supplied to define the spiral may point to the type. The regular curve section will almost undoubtedly be chord definition. I am remote now and have no access to my library, but there are a few on here that can get you pointed the right direction. Don't forget some railroads asserted and occupied a regular curve that did not match center line. The list goes on..
Good luck, Tom?ÿ
My default position would be to use a simple RR curve for the ROW, spiral curve spiral for the rails and CL construction. It looks like a VAL map not a ROW map and they were used for Tax purposes.
Using a RR curve I would put in a 1d15' curve, the mid point of that curve will be only .2' from the mid point of a spiral curve spiral so the tracks should fit well, radius of 4583.75. If you explain what you are doing in your map can't imagine anyone disagreeing.
The linked scans are really hard to read (for me), even with a magnifying glass.
Both spirals appear to be Searles spirals (1?ø spiral delta, 3 x 50 ft chords). That works out to:
Chord?ÿ ?ÿ ?ÿ ?ÿDegree?ÿ ?ÿ ?ÿDelta?ÿ ?ÿ ?ÿ ?ÿ Radius
?ÿ ?ÿ1?ÿ ?ÿ ?ÿ ?ÿ ?ÿ0?ø10'20"?ÿ ?ÿ 0?ø20'00"?ÿ 17188.739914097 ft.
?ÿ 2?ÿ ?ÿ ?ÿ ?ÿ ?ÿ 0?ø20'00"?ÿ ?ÿ 0?ø40'00"?ÿ 8594.379047316 ft.
?ÿ 3?ÿ ?ÿ ?ÿ ?ÿ ?ÿ 0?ø30'00"?ÿ ?ÿ 1?ø00'00"?ÿ 5729.596131861 ft.
I think that if you look closely at the Stations, you will find them to be 150.0 feet through the spiral.
Also, bear in mind that the central (simple) curve stationing is also a function of 100 ft. chord lengths AND the CHORD lengths of the first even [100] station POC minus the [odd] PC station value at the beginning, and the [odd] PS/PT station minus the last even [100] POC station at the end. I hope that makes sense.
Loyal?ÿ ?ÿ
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"Hickerson" Route location and design , professor from N.C State. My small gerbal wrote HP41 programs using them many years ago. I probably have an extra copy of the book. Spiral curves take some time to wrap your head around. It fitting what is found in the field, a whole different issue.
Good luck. Be safe.
Been lucky enough to find most RR information in the Region Office Design Section of TxDot.
@a-harris, there's another agency which isn't open either. Even if they had it, nobody's making copies right now.
@samlucy3874 I think I'm going to get a copy of that book. My library could use some expansion. I found a copy of one on ebay, but if you'd like to sell yours, please message me.
OOPS. I just noticed a typo in the above solution:
Chord Degree Delta Radius
1 0°10'20" 0°20'00" 17188.739914097 ft.
2 0°20'00" 0°40'00" 8594.379047316 ft.
3 0°30'00" 1°00'00" 5729.596131861 ft.
Should be;
Chord Degree Delta Radius
1 0°10'00" 0°20'00" 17188.739914097 ft.
2 0°20'00" 0°40'00" 8594.379047316 ft.
3 0°30'00" 1°00'00" 5729.596131861 ft.
It's a good thing that I am retired!
😕
Andy Nold, as expressed earlier railroad right of ways were simple curves, not spirals.?ÿ The railroads weren't obsessed about maintaining center line in the right of way on curves.?ÿ The spiral is an engineering curve.?ÿ The railroad right of way maps should show both curve data.
I've actually backed in the spiral-curve-spiral data on Val maps, figured out the degree of curve, created a simple curve for the ROW and looked at the PC-PT for that geometry and found RR right of way monuments at the PC-PT position.
They should be a rail set vertically at the PC or PT. The ROW's will be calculated with an easy degree of curve to stake so when the line is laid out the crew could add each deflection and pull the chord distance.
The one from the OP drawing calculated to a 1d15' central curve so a 1d15' simple curve would follow the construction line very well, hardly sliding from the physical tracks, I would check the TS location, the ST location and the PC PT locations for ROW rails.
These maps showed the spiral-curve-spiral data for the track construction, bridges, crossings, the little signal shacks, all the items to have property taxes calculated. But, the old right-of-ways were almost always simple curves, as it should be.?ÿ
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Search for "CC4W.net" to find excellent spiral curve reference material and software
