Are there any plans to convert train movement and safety to computer controls. For example, GPS locators on each end of the train and a computer monitoring that train’s speed/position and that of other trains.
Having full computer monitors on the individual lead locomotives could give engineers a clear picture of all trains around them.
At present Civil GPS does not have sufficient precision for railroads to rely upon it for the exact location of trains. Remember the centerline between tracks is nominally 15 feet or less.
Railroads have Million$ to Billion$ invested in their presend Computer Aided Dispatching Systems with which they operate their properties. The CADS are also integrated their corporate data processing computer systems.
Not to soud like a curmudgeon Dispatcher, however, the clearest picture that Engineers need is the Signal Indication in front of them or the Track Authority they get to operate in the so called dark territory. Too many engineers have gotten into too much trouble when their thinking begins to focus on what others are doing as opposed to what the Engineer is required to be focused upon.
Flipside, there’s been cases where engineers have saved themselves and others because they are paying attention to what’s going on around them.
Yes - one reason why CSX Rules have trains broadcast on the road radio channel signals and track autorities that they are seeing/entering.
In order for GPS location to work effectively ‘enough’, the effective constellation of satellites needs to be expanded, and backed with a network of strategically-positioned ground beacons (as high-accuracy civil GPS is now coming to use).
This has to be combined with good GIS, kept carefully updated, and then some predictive means determines how the train should be controlled for minimum fuel or brake wear, least slack action, etc. as it ‘gets over the road’. This can also include strategic speeding up or slowing down to optimize meets, passes, and terminal activities.
All this needs to be presented in a way that neither precludes or distracts from the engineer actually running their train. In some ways that’s the hardest part of the design.
PTC uses both GPS and track circuits to keep track of train locations. Our Energy Management Systems have auto throttle. The engineer engages the computer and it operates the throttle and dynamics as needed. I would be disciplined if I operated a train the way EMS does much of the time.
Engines are the only equipped rolling stock that has GPS for PTC purposes. (Some cars, especially reefers, are GPS equipped to keep track of the cars and refrigeration equipment status.)
I’ve noticed when stopped with PTC engaged at a Stop signal, the distance to that signal will change while stopped. It’s only a matter of a few feet, I think 10 feet is about the most I’ve noticed.
While running at track speed, I’ve noticed GPS is off by about one to two engine lengths when comparing the screen to the real world.
Jeff
It’s likely due to jitter in the receiver’s time standard, most likely for thermal reasons.
The clock in the receiver is what allows the receiver to distinguish between speed-of-light transmissions from satellites only a few thousand miles at most ‘differentially’ distant from the receiver, to an accuracy capable of giving the distance measurements seen.
A really good receiver will have an ‘oven’ around the time crystal, and the crystal will be cut to run at reference frequency at that temperature. But many receivers don’t have this much precision in their construction – iPhones and the like are notorious for many feet of random drift when the phone comes out of a pocket, or sunlight falls on it, or someone holds it wrong. What is pernicious is that the guidance instructions may instantly change to reflect this wack position… I think everyone has had the ‘turn left’ … ‘turn right’ (in exactly the same tone of voice) or been directed down side streets to turn around to get somewhere you passed.
“A really good receiver will have an ‘oven’ around the time crystal”
Were you an engineer (not the railroad type)? Not many people know about ovens and oscillators.
//raises hand
I was, and I do know about them. One of the last projects I was a Senior Systems Engineer on had an extremely accurate TCXO (temperature-controlled crystal oscillator) built into a data transmitter/receiver.
TCXO’s? OCXO’s? How about a Rubidium frequency standard? These are getting down to about 1 cu in and a not outrageous price. These could be of help when only a couple of satellites are in view.
Most of the inaccuracies are NOT due to the accuracy of the time standard in the receiver. As long as four satellites are in view, the position calculated in the receiver from the GPS satellites includes very accurate time. With only 3 satellites in view, the accuracy becomes degraded slightly more and more for the duration of the limited view. With only 2 satellites in view, position can no longer be calculated.
4 “birds” give you poor precision and awful accuracy . You really need 5 and a computer the size of a small locomotive to process in real time to handle the level of accuracy the OP expects in kinematic mode.
The alleged shielded main generators on the locomotives frequently aren’t and the multipath errors around locomotives are a major problem.
There are not enough CORRS stations around, especially in the stix and we still have issues with clueless engineers (they have a coordinate and no idea of how good it is … Brian probably saw that with discouraging frequency … we still do)
My race car has a GPS driven Data Logger. One of the things the logger measures is the number of GPS Satellites the device is in contact with during the recorded lap. One lap that I looked at had the logger in contact with between 8 and 11 GPS Satellites during a lap around Virginia Internationa Raceway. As Info.
It was previously stated that the accuracy of civilian GPS was only about 15 feet and not good enough for train location. If that’s true, how accurate can GPS for a race car be?
How common is it to have 8 or more satellites available to the datalogger?
Here is one of the original papers on the SA.45s CSAC when it was being marketed by Symmetricom. (The current version has a 1PPS input that lets the clock be further disciplined to ~1ns in phase and 0.5e-12 accuracy.)
I believe most of the existing modern cores can read up to 32 satellites, so the limitation is reception quality. A race or track car is likely not operating in confined spaces or where multipath is an issue… railroads would often need peak accuracy precisely in areas where satellite reception is compromised.
Right now you have a surplus of birds. Ten years ago you still were fighting to get a minimum constellation of 5 that stayed above the horizon. You had to carefully plan your work then. With GLONASS and the others now in the mix (plus servicable older birds still working), redundancy is pretty good. You still have to have the processing power to make real-time use practical.
…and then there is the issue of trees, tunnels, buildings, p-code flutters* and inertial guidance systems…GPS is NEVER going to be the solution for everything, the real world is not that simple.
(*) p-code is still messed-with by the military. Surveyors often notice something is about to happen before everybody else
Right now you have a surplus of birds. Ten years ago you still were fighting to get a minimum constellation of 5 that stayed above the horizon. You had to carefully plan your work then. With GLONASS and the others now in the mix (plus servicable older birds still working), redundancy is pretty good. You still have to have the processing power to make real-time use practical.
…and then there is the issue of trees, tunnels, buildings and inertial guidance systems…GPS is NEVER going to be the solution for everything, the real world is not that simple.
GPS in the race car is only logging data points - in the case of my equipment at 10hz. GPS does not have active control of anything.
As mudchicken postulates, the race car has full open access to the sky in all areas of the track
Nice thing about rails is that the don’t move (or at least should not) a transponder between or above the rails can give an exact reading to identify track number.