How accurate are track charts compared to real life?

[Brickrail782]

I'm in the process of making markers in Google Earth for a route I'm making, and I noticed that in many places, there is a pretty big difference between where the charts say something is located, and where it is located IRL. For example, this https://fobnr.org/wp-content/uploads/2018/09/1993prof_KansasCity.pdf (you may need to scroll down to page six, if it isn't already there) says that milepost 4.0 is located between Southwest Blvd. and Mill St., but according to the measuring that I've been doing in GE, MP 4.0 is located ~45 meters west of Mill St.

Are track charts not meant to be an exact representation of the real life, or am I misinterpreting something?

[tntrainer]

Hi Brickrail782,
The first thing I can say is that the art of surveying can be very precise and also be fraught with errors. That's a confidence building statement, isn't it? Many factors go into whether it is accurate or not. When it was done and methods used can be a factor and I have to imagine the technology of today is far more precise than a document created 150 years ago or even in 1993 as your profile was. Even it was probably created transferring a lot of info from previous versions rather than new measurements. I have to admire the way it was done in years past without GPS, satellite imagery, and all the electronic devices in use today. In the early days the surveyors used poles with a 100 foot chain in between to mark "stations" where some key point of demarcation was needed. In these images of profile charts and tax maps I am using to create my route, you will see these "stations" where I have used an arrow. So for instance mile 144 is at 7649+80. That is 7649 stations plus 80 feet. Its a simplified way of saying 764,980 feet from the STARTING point say for instance.... milepost 0.0....
The catch is there are errors in anything mechanical such as walking and measuring with a 100 foot chain, obviously. How can we prove this? Subtract the station number for 144 from 145. The answer is 5316. A mile is 5280. A difference of 36 feet longer. The next mile also has an error of 3 feet, the next is 75 feet short.....
How did this happen? WHO KNOWS for sure. Maybe Fred and Bubba missed the spot when they installed the third new milepost over 100 years. The mile markers are used for reference more than accuracy. Most railroad timetables have "measured miles' used to check the accuracy of speedometers. This is because they know the majority of mileposts could be wrong. The mile could have fallen where there is a road, a creek, a boulder, a switch stand. They would place it as close as possible but it may not be exact. The red and blue circles show the elevations at grade change which is handy. On my chart they are simplified to the "tens" with the "hundreds" only being at the change point. Your chart appears to show the whole number. Style differences with the era of the chart and the Chief Engineers preference.

Chatt Sub 002.jpg

This is a small snippet of a Right Of Way And Track Map from the N&C Railway. It is for the route I am creating in TSXX and acquired from the State of Tennessee tax department website. It shows greater detail that a profile chart might not have giving the "station" numbers for every culvert, tile, bridge, point of switch, siding, milepost, road crossing, water tank, etc etc etc.
They are huge maps detailing only a couple miles usually. They have the curvature but not grades. They also give higher detail of ownership, property rights, and locations of structures to the STATION! Very useful if your going overboard on precision. I'll comment on that below.

Example 001.jpg

Example 002.jpg

SO how accurate are we going for? 99% of the people who will run the route (if you share it after it is completed) will never know if you are 100% on the accuracy of the representation you are creating in the simulator. I doubt that they would have any way of knowing. My position would be use the charts for the key information they contain, curvature, grades, elevations of the track, siding location and arrangement, and approximate mile posts. If you become too attentive to complete accuracy, you may never complete the project and get frustrated with lack of progress. I use the Google overlay and try my best to lay the track based on that. Part of this route has been abandoned for 50 years now. So using Google is looking at tree lines and fence rows in some cases. The profile chart tells me what was there in that era too. I do use the curvature and grade info to set those but, that's about it as far as actual position of the railroad from a profile chart. Google is REAL LIFE. It might not be the exact era we are shooting for but it is real. Yes, I have tried to set the mileposts according to my station numbers on the charts too. I also look for them in the overlay and sometimes find them.

I'm a novice at building routes but I have really gotten into that aspect. More than doing a repaint or creating a 3D model to add to the world. I'm sure other more experienced route builders will speak up and offer good opinions. I am a career railroader and work on and inspect track, bridges, and right of way, so I feel I can comment on the technical aspects of the charts. That's my

Happy to comment further and good luck with the route,

George

[tntrainer]

I would also say I noted your chart did not have stations listed. If you could find an older version I bet it does. Not really important except in the context of proving the accuracy of any point. I'm sure they have engineering drawings with stations and such at BNSF. They have chosen not to go into that detail on the 1993 charts. We have to work with what's available to us, right? I would bet money that when they check a point in real life today, some of those are based on points created over a hundred years ago. Its just easier for them to find with GPS today.

[BoostedFridge]

I'm in the process of making markers in Google Earth for a route I'm making, and I noticed that in many places, there is a pretty big difference between where the charts say something is located, and where it is located IRL. For example, this https://fobnr.org/wp-content/uploads/2018/09/1993prof_KansasCity.pdf (you may need to scroll down to page six, if it isn't already there) says that milepost 4.0 is located between Southwest Blvd. and Mill St., but according to the measuring that I've been doing in GE, MP 4.0 is located ~45 meters west of Mill St.

Are track charts not meant to be an exact representation of the real life, or am I misinterpreting something?

The track chart is correct in the location of the milepost. MP 4 is slightly (~35m) east of the Mill Street crossing.

The mile numbering on the signal bungalow corroborates this.

MillStBungalow.JPG