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Free eBook: Testing GNSS receivers for railway use

eBook Cover GNSS Receivers for railway use

The use of GNSS receivers in the rail industry may be in its infancy, but the potential impact of GNSS technology on our railways is huge—from ushering in new levels of efficiency and safety, to dramatically enhancing passenger information services.

Download a free eBook to discover:

  • The safety-critical railway applications of GNSS
  • The unique GNSS challenges of the railway environment
  • The solution to the high costs and limited scope of field testing

Simply enter a few details opposite to receive your free eBook—and happy reading!

About Spirent

Spirent has been the global leader in GNSS testing for near 30 years. Spirent delivers navigation and positioning test equipment and services to governmental agencies, major manufacturers, integrators, test facilities and space agencies worldwide.

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    Testing GNSS receivers for railway use Testing GNSS receivers for railway use 1 Why use GNSS on railways? The use of global navigation satellite system (GNSS) receivers in railway applications might seem strange. After all, with a vehicle on fixenullrails, there is little scope for navigation. nullut the availability of precise positional information for each train, or even each carriage, in a railway system can enable new levels of efficiency, safety annull improvenullinformation services for passengers. Page 2SPIRENT eBook 2 Safety-critical applications nullany of the potential railway uses for GNSS navigation will involve safetynullfnullife applications. These inclunullnull • Positive train control, used either as a supplement to, or as a replacement for conventional line-side signalling and control systems • Automatic door operation • Train integrity and separation control • On-train monitoring and recording • Train protection and warning systems • Off-train infrastructure protection (level crossing operation, end-of-line stop limits) SPIRENT eBook 3 Problems with the railway environment Any GNSS receiver operating in a railway environment will face three specific challenges to normal operationnull Signal obscuration – caused by tunnels, deep cuttings and overhead structures such as station canopiesnull Multipath effects – caused by signals being renullcted by tracnullide structures (particularly in urban environments)null Electromagnetic interference – from both enullernal nullrcs and sparnullnulland from other on- train enullipmentnull Any one of these phenomena can challenge the accuracy annullintegrity of an unprotectenull or uncompensatenullGNSS receiver. Page nullSPIRENT eBook null nullulti-GNSS opportunities The GNSS lannullcape is changing. nulln anullition to the longnulltannullng nullnull controllenullGnull, new systems are beginning to come online. These inclunull GnullnullASS (nullussia), Galileo (nulluropean nullnion) annullnullmpass (nullina), annullwill be nullinenulllater by a new annullimprovenullGnull. There are two implications for this expannullng ecosystemnull null nulllti-nullnull receivers capable of processing signals simultaneously from multiple satellite systems will offer improved global coverage and more reliable performancenull null nullme of the new systems, such as nulllileo and the modernised nullnull will offer higher- integrity signals (for a fee) that will be more suitable for safety-of-life applicationsnull SPIRENT eBook null The importance of testing nullegarnulless of which GNSS is chosen (annullof whether the navigation system is GNSSnullnly or augmentenullwith inertial or other sensors) any railway navigation system will renullire extensive testing to nullliver the confinullnce renullirenull This testing will be necessary throughout the lifecycle of the pronullct, coveringnull nullnullstem testing from nullnullto verinullation, production and deployment null Performance assessment, both in nominal and adversarial conditions nullnullstem or unit calibration null nullstem verinullation and certinullation to prescribed standards nullnullpair and fault diagnosis for enullipment in the nullld Page nullSPIRENT eBook null The problems with nulllnulltesting Although it might appear that the logical methonullfor testing a GNSSnull basenullrailway navigation system is to mount it on a train annulltest it in the fielnullusing nullivenullnullnullsatellite signals, this approach has several serious shortcomings, inclunullngnull nulligh costs nullthe cost of obtaining rolling stocnullannulleffectively shutting nullwn a section of railway line to perform testing can be astronomical. Page nullSPIRENT eBook No repeatability nullthere is little point in performing any test nullst once, annullno GNSS test is fully repeatable in the fielnull(even if the same motion profile coulnullbe replicatenull the positions of the satellites usenull will never be replicatenull. nullmitenullscope of testing nullas there is no reliable way of recreating abnormal or anullersarial operating connulltions, the receiver can never be testenullto its limits. Page nullSPIRENT eBook null The simulation solution The alternative is to test the unit in the controllenullenvironment of the laboratory using an null constellation simulator unnullr software control. nullnlinull livenullnull testing, the simulation solution offersnull nullenullcenullcosts nullwith no neenullto source rolling stocnullor shut nullwn busy rail lines nullmplete repeatability nullas tests are performenullunnullr software control, each one can be savenull annullrepeatenull right nullwn to the positions of each of the satellites Winull scope of testing nullwith unrestrictenull ability to create abnormal test connulltions, receivers annullsystems can be testenullto the extremes of their performance Page nullSPIRENT eBook null Testing with a simulator Tonullynulls multichannel null simulators are capable of simulating all current annullfuture nullfinenullGNSS signals, annullso can be usenullto nullvelop annulltest tomorrownulls systems tonully. Sophisticatenullsoftware allows users to automate simple iterative testing tasnull as well as creating complex test scenarios, inclunullng simulatenullmotion, simulation of terrain effects annullsimulation of obstructions, inclunullng multipath effects. Simulators can be combinenullwith other instruments, such as interference generators, to create a variety of abnormal operating connulltions to test GNSS receiver basenullenullipment up to annull beyonnullits limits of performance. Page 1nullSPIRENT eBook null nullilway nullalinullation nullile no specific stannullrnullyet exists for the use of GNSS receivers in a railway environment, it is inevitable that when such a stannullrnull is pronullcenull it will mannullte the use of null simulation as the test methonulllogy. New stannullrnull for the use of Galileo receivers are beginning to appear, such as nullnullnullnullnullnullGalileo nullnulleceiver enullipment null nullerformance renullirements, methonull of testing annullrenullirenulltest results, which mannulltes the use of null simulation in testing nullvices for use in the maritime sector. As a result, enullipment manufacturers can base their nullvelopment on simulator testing using the same test methonulllogies that are employenullin the test stannullrnull. This means that their nullsigns will be much more linullly to meet the renullirements of the stannullrnull. Page 11SPIRENT eBook 10 The future nullile the use of GNSS receivers in the railway innullstry is still in its infancy, null simulator manufacturers can have a manullr role in helping to anullance nullvelopment, inclunullngnull • nullaluating real-world data on railway nullurneys in order to create scenarios for use with simulatorsnull • nullmparing nullld-test results with simulated results Annullprovinullng expertise to support stannullrnull annullcertification nullvelopment for GNSS railway applications. Page 12SPIRENT eBook nulle hope you founnullthis Testing GNSS receivers for railway use nullnullonullof interest. nulle are continually anulling new content to our website on a regular basis. nullonullarnullthis linnull www.spirent.comnullositioning nullisit the Spirent GNSS nulllognull there are currently more than null posts with nullto nullnew posts anullenull per weenull nulltch up on whatnulls newnull www.spirent.comnulllognullositioning Neenullmore informationnull gnssnullolutionsnullpirent.com Sharenull nullaceboonull nullnnullnulln Twitter Technorati Google nullunull nulligg nullelicious nullenullit Stumbleupon null Spirent nullnullnullnull nullnullnull globalsalesnullpirent.com www.spirent.comnullositioning Spirent nullenullral Systems null nullnullnullnullnullnull infonullpirentfenullral.com www.spirentfenullral.com Got a smartphone? nullan the null nullde for more information