I’m wondering if the RR’s use any small portable devises to measure the grade at any given location of the track?
The measure the angle the sleeping conductor’s head is at…
The way they recently did it at the Cass Scenic RR was taking a hand held GPS device, going up track 100 feet, and calculating the grade. The previously marked 11% grades were now found to be no greater than 9%…
Phil
Having used my GPS to verify grades on our railroad, I question the accuracy. I’ve passed the same point several times with the GPS and have gotten different elevations each time. For that matter, I’ve placed the GPS on a solid surface, with excellent satellite coverage, and watched the elevation change as it sat there.
As for the original question - very easy to do. Set up a surveyers transit, make sure it’s level, then shoot a point some distance away (100’ makes for easy calculations). Using the standard surveyors stick, it’s easy to determine the rise or fall (ie, grade).
You could do the same thing yourself using a common carpenter’s level (2’ or more), your camera tripod or other suitable stand, and an 8’ stick or board.
Set up the level so it’s level and pointing at the second point you want to measure. You’ll need to find out how far it is from the ground to the top of the level, and mark that distance from the bottom of your 8’ stick/board.
Measure out 100’ and stand the stick/board there. With one person at the level and the other at the stick, sight across the top of the level and have the person at the stick mark that point on the stick. There will be some calling of “up,” “down,” etc, but it wont take too long.
Measure the distance between the two marks. One foot will equal 1%, six inches will be 1/2%, two feet will be 2%, etc.
If you want to do the calculations and have a transit that measures vertical angles, you could simply measure the angle between points and figure it out that way, too.
Given a 100 foot chain and a transit which also measures horizontal angles, a crew can determine grade and curvature quite quickly for a pretty good distance.
As for the Cass - I think I’d trust the transit more than I’d trust the GPS. Given the margin of error I usually see displayed on my GPS, it’s not u
Since most tracks have been down since before GPS I would assume that the surveyers who laid out the route also figured the grade with a transit. Having helped layout a steel mill line over 3/4 of a mile long the accuracy astounded me. You can hold an 1/8 of an inch over that distance. In the case of elevation simple trigonometry will allow you to calculate the rise by knowing the distance and the angle of it. I would also assume that some grades have varying degrees of pitch and are not consistent over the entire grade.
…I would imagine most grades were intended to be a constant grade for a given distance and not weaving up and down on it’s way. That is if it was not built on the cheap. Of course the grades are compensated on curves {lessened}, to allow constant drag on certain up grades.
I too have always been amazed {and then some}, the accuracy of surveying over long distances and also in extreme circumstances such as building tunnels {and digging from both ends, etc…}, and meeting in the process, perhaps near the center with accuracy enough to be just inches off of exact meeting.
The Chunnel in England’s English Channel crossing comes to mind.
But to go beyond that, much of the infrastructure {RR}, was done under less than good conditions over a hundred years ago. Which adds to it as well…!
I agree with Larry re: GPS signals can wonder…Have seen it right here in my drive way as the instrument was stationary, figures moved up and down. But {in a built in one}, it sure did show the vehicle was pulled right into my driveway…!
Other than standard surveying instruments? No. It would be pointless. If you want to know the grade you look at the track chart. If you need greater accuracy you call a surveyor.
RWM
Unless you have a surveying grade quality device (several thousands of dollars) using a GPS device will not give you accurate enough measurements to calculate grade. Its only good to plus or minus several feet. So your 9% measured grade is somewhere between 12% and 6%. And that assumes that the same offset of error at both ends. If the down end measured high and the up end measured low the difference could be even more. Since the grade was probably measured by traditional surveying methods to begin with, I would go with them. they would be accurate to inches, whereas handheld GPS is only accurate to feet.
Over long distances (miles) the couple feet error isn’t as big a factor. Railroads use traditional surveying methods, high accuracy GPS surveying or low accuracy GPS over longer distances to calculate grade.
Dave H.
…GPS is a very important instrument in position location in emergencys. A few years ago over in our home location of Pennsylvania the location where to drill a rescue bore to get to trapped coal miners…{down 240’}, was very much assisted by GPS as time was of essense. The bore broke thru the mine cavity right where it needed to and a rescue was accomplished. One might remember the famous line from that resue…“9 for 9”…meaning all envolved were rescued alive. That was the Quecreek, Pa. location.
Quentin, GPS is useless in mine surveying because there is no reference point inside the mine because there is no radio signal inside the mine. Mine surveying uses traditional techniques.
RWM
[(-D] [(-D] [(-D] [(-D]…Good one!
He meant using GPS to know where to drill the rescue hole from the surface down, not for mine surveying. Try reading the entire post next time.
…RWM:
Reread my comments…GPS was used to position the drill to do the 30" bore down to the mine cavity. I didn’t say it was used in the mine. It was used to find the location the miners were thought to be, and…they did correctly hit that cavity the men were trapped in.
Railroad grades were (are) established by locating engineers with criteria given them by the RR’s Chief Engineer who is also given criteria (keep construction cost down - ruling grade - etc.). In the 19th century keeping initial construction costs low was a dominate theme and thus many changes to the original construction have occurred over the years.
When Santa Fe elected to relocate 44 miles of the TRANSCON between Williams and Crookton Arizona in 1959-1960 the gradient criteria chosen was ’ no grade at any point will be greater than 1% (compensated) '. And at the location where a minus 1% gradient changed to a plus 0.88% a 10,000 foot vertical curve was created for the purpose of minimizing slack action. This kind of 20th century engineering did not have a ’ low cost ’ theme and was consistant with the continual upgrading of the TRANSCON. It is one illustraion why the TRANSCON is so heavily utilized today.
Zeiss level instruments and a level rod were the tools used at Williams, not a transit which was used solely for alinement.
I read your post both times, Quentin. I think we’re talking around each other. While GPS is useful to find an underground location that is already mapped, it’s of no good otherwise in underground mine surveying. Having a mine map in hand, you can use GPS to reference yourself to a surface location, but I’d back that up with traditional surveying if it was my reputation and money on the line.
(So far this year I’ve spent more than $250,000 buying surveying services … and to quote my friend Mudchicken there’s darn few surveyors that have a clue around railroads. I’d rather send a railroad-knowledgable surveyor 1,000 miles to the project site than hire a local who “might” know what they’re doing.)
RWM
Well, now we know where the idiots reside.
West By God Virginia
…RWM:
Fair enough. With maps in hand and the GPS to get the surface position located {quickly}, it wasn’t money that was on the line…it was human lives…There wasn’t time to do all the land surveying you mention. So GPS was employed and as I stated earlier, it hit the pocket cavity the men were trapped in dead on. They started two rescue bores and one had trouble with breaking equipment {drilling bits, etc…}, and the other was as I’ve been saying…successful. All 9 men came out alive in a rescue cylinder…! Of course, one at a time.
Edit: A smaller bore was sunk first to validate the location. Then the serious bore size needed was put down…No easy task…around the clock by super human efforts.
Level (wye and-or dumpy/tilting dumpy) and babbit faced steel chain - no transit. Most 1840’s-1880’s engineer’s transits did not even have a vertical circle. A Parkhurst theodolite would have been impossible for railroad crews to move around with any economy. The 1873 Gurley Engineer’s Transit in my living room does not have one. Even with today’s electronic instruments, trig-levelling normally is not used (and we often use conventional levelling techniques with second order levels to find errors in local GPS networks or ignore GPS vertical readout entirely). Optics and collimation issues can eat your lunch. Those old railroad mudchickens did their job by repeating measurements and level loops over and over again over the same piece of ground.
With GPS, your timing signal can be interfered with in so many ways (multi-path, etc.), especially in the vertical. The comparison of vectors can throw you way off. “P” codes can be interfered with. If you have no concept of how the equipment you are using works and what your limitations are, you are what most surveyors refer to as a “button-pusher” with zero technical credibility…
Well, that’s what the loggers thought the grade was, and who was going to challenge the loggers’ reliability?? Turned out, the local historian, who back in the **60’**s told everyone their grades were wrong…
Phil