I have a Colorado DOT Right of Way map that was done in 1908 latest revision 1930.
The curves are stationed at the PC, PI and a BACK/Ahead at the PT. The PI is PC+T and the BACK=PC+L But what I need is the Ahead Station. I have the P.O.T. point to the right edge of the following picture, and I need to get through the curve.
You may or may not be able to read anything in this picture.
Another curve in the same set of plans yields PC+2T=Ahead, but that answer does not look right with whatever is there no matter how much my imagination is tweaked.
> Another curve in the same set of plans yields PC+2T=Ahead, but that answer does not look right with whatever is there no matter how much my imagination is tweaked.
PC+2T would make sense if they ran the stations before the curves were designed. Then, they added the curves, and a station equation (back & ahead) was required at each PT in order to match the previously run stations.
You're correct, nothing is legible on the plan.
Ditto! I've seen that.
From the field book Stations PI to PI. Back off tangent distance for PC
for the plan add arc length for the PT & Station Equation at the PT.
I have seen the same on highway plans made before 1930. In addition these plans had buildings near the curve stationed from the fore tangent rather than the curve. Appeared that all topo needed for design was located from the tangents and the curve designed to miss existing structures.
EDIT: The plans were from the Ohio inter-county highway system that predated the 1930s formation of the Ohio Department of Highways. These were joint state/county funded roads.
I downloaded the rest of the sheets of this plan set. The equation stations on the curves I can read do not seem to have any consistency. The PC+2T curve is the only one like that. There is one 1 degree curve that has no equation. The remaining six curves are 6 degree curves, two of them the ahead station is an average of PC+L and PC+2T, one is completely illegible and this one and one other seem to be random numbers.
