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Re: PTC not solely dependent upon GPS?
Author: BOB2
Date: 12-19-2009 - 08:39
Yes it is a partially GPS based system, it is not dependent solely upon the GPS coordinates for location, it is to be designed, to compare the GPS information to the on board data base, and line side inputs.
The system data bases and accurate locational data containd in them are probably a more critical element to the success of PTC, than the issues raised by the relative accuracy of GPS. In some regimes, only very limited confirmational information is needed, in more complex operating environments, higher levels of information can be gathered-like track cicuit conditions using DSRC technologies for things like signal indications, track occupancy, or even fault detection systems. This multiple confirmation of multiple data inputs and operator response is where the safety and operator oversight happens.
The route surveys that create this on-board data base, for GPS and inertial confirmation, are underway on several properties already.
I usually find OPB's input very well informed, but in this case, I find the concerns to be based upon what appear to me to be some minor issues with only part of the system, the relative accuracy issues with GPS. As to the relative accuracy of commercial GPS, I've often been able to calibrate locations to within 10 cm of confirming USGS bench marks, in the bus and truck tracking projects I've worked on. This is not a guaranteed accuracy, which is usually 3 meters, and may be as much of a function of the mislocation calculation error of the actual benchmark (triangulated with old fashioned ground survey techniques), as to the ethereal vagaries of the range of likely wavelength variance, interference, or the relative wobble of the statellites and the earth?
I do have a concern that we may be creating some standards for PTC which may not be fully "open", but may impose less competitive "proprietary" characteristics, through the regulations. This would potentially add excessive monopoly contractor profits, from the limited innovation and competition, to the costs. I've seen this use of proprietary standards to benefit specific vendors attempted, through political influence being exerted, in other applications of ITS technologies. But, America's railroads are woefully behind other rail systems in adapting advanced technologies for safety and efficiency in operations. Years of decapitatlization have created a corporate culture of doing little except making do with antiquated systems.
We need our railroads again, and it is time to make sure that they are brought into the 21st Century. As to the cost effectiveness? Well Chatsworth alone will test the $200 million liability limits, and we have been frankly lucky with several avoidable hazmat incidents in major urban areas, that could have been catastrophic. PTC also increases not just safety, reducing significantly the liklihood of avoidable liability costs, but also can greatly increase speed and capacity, if used properly, increasing operating efficiency. So I don't buy the "sky is falling" no ROI on PTC nonsense, either.
The system data bases and accurate locational data containd in them are probably a more critical element to the success of PTC, than the issues raised by the relative accuracy of GPS. In some regimes, only very limited confirmational information is needed, in more complex operating environments, higher levels of information can be gathered-like track cicuit conditions using DSRC technologies for things like signal indications, track occupancy, or even fault detection systems. This multiple confirmation of multiple data inputs and operator response is where the safety and operator oversight happens.
The route surveys that create this on-board data base, for GPS and inertial confirmation, are underway on several properties already.
I usually find OPB's input very well informed, but in this case, I find the concerns to be based upon what appear to me to be some minor issues with only part of the system, the relative accuracy issues with GPS. As to the relative accuracy of commercial GPS, I've often been able to calibrate locations to within 10 cm of confirming USGS bench marks, in the bus and truck tracking projects I've worked on. This is not a guaranteed accuracy, which is usually 3 meters, and may be as much of a function of the mislocation calculation error of the actual benchmark (triangulated with old fashioned ground survey techniques), as to the ethereal vagaries of the range of likely wavelength variance, interference, or the relative wobble of the statellites and the earth?
I do have a concern that we may be creating some standards for PTC which may not be fully "open", but may impose less competitive "proprietary" characteristics, through the regulations. This would potentially add excessive monopoly contractor profits, from the limited innovation and competition, to the costs. I've seen this use of proprietary standards to benefit specific vendors attempted, through political influence being exerted, in other applications of ITS technologies. But, America's railroads are woefully behind other rail systems in adapting advanced technologies for safety and efficiency in operations. Years of decapitatlization have created a corporate culture of doing little except making do with antiquated systems.
We need our railroads again, and it is time to make sure that they are brought into the 21st Century. As to the cost effectiveness? Well Chatsworth alone will test the $200 million liability limits, and we have been frankly lucky with several avoidable hazmat incidents in major urban areas, that could have been catastrophic. PTC also increases not just safety, reducing significantly the liklihood of avoidable liability costs, but also can greatly increase speed and capacity, if used properly, increasing operating efficiency. So I don't buy the "sky is falling" no ROI on PTC nonsense, either.
