OK, I might just be having a brain fart and can't see the forest through the trees so bear with me.
What does CH DIST. mean on the attached image?
On the south side, the ROW appears to be 165' but at the PC and PT there is a callout for 164.8 and 164.90 respectivly. Also on the north side, there is a callout for +25/ 141.44 and then another call to the same point for CH DIST 141.70. On the south is a call for +38/ 165' and another call for CH DIST 165.30
I'm trying to figure out the north side and hoping I can get some clarity on this. MoDOT is no help at all.
Thanks.
"chord distance"?
Meaning the distance from the ROW line to the chord of a curved centerline/baseline.
If the number in question is an offset to a curved centerline, then the offset to the chord of the centerline could be either larger or smaller, depending upon which side of the curve you are on.
My first thought would be chord distance.
I see Silicon Cowboy beat me to it.:good:
My guess is "chained" distance as in measured.
Interesting but that doesn't seem to make sense either. In this instance, a distance to the chord of the curve would result in differences of several feet. This reference is made in tanget sections of roadway as well.
Not sure what the "CH" is but it looks like it is hand written on the page. It might be a check distance from someone to a metal R/W post. Depending on where they were able to get a shot has a affect on the distance to centerline.
Did you try calling the District Office in St. Louis and asking for the District Land Surveyor? Usually they are willing to help out on something like this.
That could be. It would be pretty sloppy tolerances especially since the map represents newly acquired ROW. Par for the course from my experience.
I haven't tried that route yet. Thanks. The people manning microfilm and even ROW department are of little knowledge and help.
The "CH Dist" notes seems to have been written after the fact by someone other than the original draftsman. The lines are not ruled, the notes are jammed into odd spaces, and the lettering is different. So you may be looking at a copy of a drawing that was marked up for field use in staking out ROW points. Such a marked-up drawing, if that's what it is, ought not to be used as a record copy, but maybe it was the only one they had left.
The C/L radius of the 1 degree curve is that of a 100-foot chord definition curve. The middle of a 100-ft. chord on such a curve comps to be 0.21 inside the arc, which seems to explain at least a couple of the "CH Dist" figures on the South side, i.e. 164.8 from the chord rather than 165.00 from the arc. The North side ROW is not concentric, of course, so it's harder to tell if this hypothesis would fit.
The angles of 84-04 and 95-42 and the accompanying stations and offsets are clearly after the fact, which again suggests that they were computed for field use.
If you were to compute the ROW points based on the original draftsman's dimensions, you might be able to check this hypothesis and come up with an explanation for the apparent field dimensions.
In Minnesota the DOT used to file ROW documents containing metes-and-bounds descriptions corresponding to the ROW geometry shown on the drawings. I don't know if that's done in Missouri, but if so those descriptions might enable you to check the "official" ROW geometry and separate it from the apparent field comps.
I have the impression that the field comps might be sort of quick and dirty, and may contain some errors.