Western Railroad Discussion > PTC/GPS Issues on Sunday

On my way to Montana Sunday I heard several trains reporting PTC issues, where the map suddenly went away and they couldn't get it back. Both the PTC desk and the dispatcher admitted to widespread issues. The dispatcher said the GPS issues were "planetary". The typical solution offered was to cut out the PTC, run for 20 miles and try to cut it back in.

Ted Curphey
Ontario, OR

I heard the BNSF PTC desk discuss the same issue with a train in central Oklahoma on Sunday.

Ken Brown
 

funnelfan Wrote:
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> On my way to Montana Sunday I heard several trains
> reporting PTC issues, where the map suddenly went
> away and they couldn't get it back. Both the PTC
> desk and the dispatcher admitted to widespread
> issues. The dispatcher said the GPS issues were
> "planetary". The typical solution offered was to
> cut out the PTC, run for 20 miles and try to cut
> it back in.

One of my fundamental criticisms of the recent NTSB DuPont hearing and report is that the chanted the PTC Mantra, then criticised Sound Transit, Amtrak, BNSF, and even WSDOT (clue, they don't have a railroad, they have trains and hire railroads to operate them), then the railroad industry in general for not bothering to implement PTC, and even Congress for letting them get away with it.

Once again, we have....

TAW

"The dispatcher said the GPS issues were "planetary". "

Incredibly broad but basically correct. There's a number of GPS Satellites used to make a location determination, if any of the radio signals give a problem the whole calculation could be corrupted. I'm not sure how the RR equipment uses the GPS signals, whether it dumps if one is corrupted or if they can use fewer signals. Agree they seem to be having an awful lot of problems. In Northern California they have a problem with PTC determining that a wheel slip, or possibly an unusual change in the GPS reception or calculation to be an overspeed condition which requires a PTC/Software intiated emergency application, dumping the air.

There are a number of smartphone Aps that you can use to check individual GPS Satellite/Signal performance, if you're really in to it. In my line of work there had been an attempt to use GPS as a time standard at remote Test sites, we also used it to confirm Customer site locations. Eventually we just used the hard wire Internet time and tossed out all the junk RF hardware a Contractor had built for us. We would still verify the Google Map coordinates though.

There doesn't seem to have been any solar events, outages or interruptions reported on Sunday.

Solar weather:  https://www.swpc.noaa.gov/

reported status: https://navcen.uscg.gov/?Do=GPSReportStatus

Coast Guard reported status, there are some events on other days in there: https://www.navcen.uscg.gov/?Do=constellationStatus

Planned Interference due to Testing: https://www.navcen.uscg.gov/pdf/gps/gpsnotices/GPS_Interference.pdf

There are a couple of newer GPS Satellites up there this year but I don't know what their status would be. I have been meaning to check that out though.

Looks like quite a few reports have come in as far as decreased accuracy on GPS for PTC receivers:
https://navcen.uscg.gov/?Do=GPSReportStatus   (search for train)

The short version is that NAVCEN's response has basically been: "We didn't change anything and this doesn't correspond to GPS degredation tests, satellite outages, or space weather anomalies, so go talk to your receiver manufacturer."



 

Yes, good catch. The RR's are discussed in the CG report but not on that particular Sunday.

Not obvious whassup. PTC also has layers of Software behind the error messages, just like a Boeing 737. Hopefully not the same folks writing the code.

+  Interesting point is made how the RR data could be used to 'map' GPS performance across the reporting area. They also point out that there seems to be an overall error in the RR equipment, that could be a simple calibration standard that has corrupted all the receivers in the field, but somebody at a higher pay grade should have figured that out already.

++ btw GLONAAS is the Russian version of GPS. It was said, at one time, to be capable of making GPS data invalid. Same for the EU version, the intials of which elude me at the moment.



Edited 1 time(s). Last edit at 07/01/19 21:01 by TCnR.

This morning towards the end of my trip, in the last 20 miles, PTC decided to throw a "SIGNAL STATUS UNKNOWN," message regarding the clear signal that we were rapidly approaching at 60 mph.  It promptly put us into penalty, then when it realized it wasn't going to stop in time it threw us into emergency.........for a clear signal.   Such a wonderful and reliable system.

It will be hard to walk the train after the emergency brake application once single person crews are instituted unless that rule is tossed out as well.

TCnR Wrote:
-------------------------------------------------------

> ++ btw GLONAAS is the Russian version of GPS. It
> was said, at one time, to be capable of making GPS
> data invalid. Same for the EU version, the intials
> of which elude me at the moment.

Galileo. 

Mmmm, good omens for self-driving cars and trucks, eh? === === = === JLH

HogheadMike Wrote:
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> This morning towards the end of my trip, in the
> last 20 miles, PTC decided to throw a "SIGNAL
> STATUS UNKNOWN," message regarding the clear
> signal that we were rapidly approaching at 60
> mph.  It promptly put us into penalty, then when
> it realized it wasn't going to stop in time it
> threw us into emergency.........for a clear
> signal.   Such a wonderful and reliable system.

I've had that happend and still skated past the signal and into the crossover by three car lengths, so what good is it.

highgreengraphics Wrote:
-------------------------------------------------------
> Mmmm, good omens for self-driving cars and trucks,
> eh? === === = === JLH

Will be even worse when people have forgotten how to drive, or never had to learn.

mapboy

They still don’t know how to drive.

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