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Application Note: Fundamental GNSS Receiver Characterisation

Fundamental GNSS Receiver Characteristics Cover

GNSS technology continues to find new and unexpected applications—and to change our relationship with even the most everyday devices. But as we become increasingly reliant on GNSS technology, the consequences of it failing become increasingly severe.

With the stakes rising, it is crucial that manufacturers of GNSS-enabled equipment are able to accurately and comprehensively test the performance of their GNSS receivers throughout the development process.
Download the Application Note to discover how designers, developers, integrators and testers can:

  • Understand the key performance parameters of GNSS receivers
  • Run controlled, repeatable simulations to assess and enhance receiver performance

Simply enter a few details opposite to receive the Application Note—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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    Fundamental GNSS Receiver Characterisation APPLICATION NOTE Spirent Communications PLC Paignton, Devon, TQ4 7QR, England Webnull httpnullnullnullnullpirentnullomnullositioning Telnull null4 nullnull nullnullnull nullanull null4 nullnull nullnullnull Copnullight nullnullnull Spirentnull nulll Rights Reservednull nulll onullthe compannullnames andnullr brand names andnullr product names renullrred to in this document, in particular, the name nullpirentnulland its logo device, are either registered trademarnull or trademarnull onull Spirent plc and its subsidiaries, pending registration in accordance nullth relevant national lanullnullnulll other registered trademarnull or trademarnull are the propertnull onulltheir respective onullersnull The innullrmation contained in this document is subnullct to change nullthout notice and does not represent a commitment on the part onullSpirentnull The innullrmation in this document is believed to be accurate and reliablenull honullever, Spirent assumes no responsibilitnull or liabilitnullnullr annullerrors or inaccuracies that manullappear in the documentnull Page 2SPIRENT Application Note Contents nulludience 4 nullntroduction 4 RnullSimulation null Tnullical nullS Simulators null nullundamental Receiver Pernullrmance Parameters null Cold Start Time To nullirst nullinull null Simulator test null Warm Start TTnull 7 nullot Start TTnull 7 nullcnullisition sensitivitnull null Tracnullng sensitivitnull null Reacnullisition Time null Static nullavigation nullccuracnull null Dnullamic nullavigation nullccuracnull null Radio nullrenullencnullnullnternullrence null Conclusions null Renullrenced Documents null nulllossarnullonullTerms null Page 3SPIRENT Application Note Audience This nullpplication nullote is nullr designers, developers, integrators and testers onull nullSS receivers or snulltems, nullo need to ensure their products nullll pernullrm in the intended environmentnull Spirent recommends nullou have a basic understanding onullsatellite navigation principles and anullreness onullRnullsimulation as a test method is desirablenull Introduction There is a steadnullgronullh in the use onullnullSS in nenulland enullsting marnulltsnull Consenullentlnull, there is an increasing reliance on nullSS technolognullnull With this in mind, it is important nullr designers, manunullcturers and consumers onullthese products to understand nullat to enullect nullom such snulltemsnullThis includes nullrmulating an understanding onullthe limitations and problems onullnullSS technologiesnull This nullpplication nullote discusses some onull the nullndamental receiver pernullrmance parameters applicable to nullSS snulltemsnull Complementarnullto this, it demonstrates honullSpirentnulls range onullnullSS Test Solutions enable nullou to create and run controlled and repeatable simulations and benchmarnull nullour receivernulls pernullrmance nullen subnullcted to these errorsnullnullt demonstrates that a nullSS RnullSimulator is able to generate the conditions renullired nullr pernullrming suitable testsnullThe application determines the test criteria, and the importance onull each criteria manullvarnullsigninullantlnullnullom one application to anothernull nullor enullmple, short TTnull pernullrmance manullbe vital in automotive applications, but not so important nullr static position survenullngnull Renullcnullisition is probablnull not a primarnullconsideration nullr marine applications, nullere little phnullical enullernal signal obscuration enullsts, but is important in automotive applications nullere tunnels and bridges nullenullentlnullblocnullsignalsnull Page 4SPIRENT Application Note RF Simulation null RnullConstellation Simulator reproduces the environment onulla nullSS receiver on a dnullamic platnullrm bnullmodelling vehicle and satellite motion, signal characteristics, atmospheric and other enullnullcts, causing the receiver to actuallnullnavigate according to the parameters onullthe test scenarionull nullnullits vernullnature, simulation is a representation onullthe real nullrldnull Simulation cannot reproduce the nullll richness onullreal nullrld conditionsnull null common misconception is the need to enullctlnullreplicate real nullrld conditions nullr a nullSS test to be validnull nullonullever, application onullrepresentative enullnullcts via simulation is proven nullver some null nullears onulltestingnullto enullercise receivers and adenullatelnullidentinull their limitations allonullng nullr design centring and optimisationnullnullore importantlnull, it gives complete repeatabilitnull, control and enullct nullonulledge nulldonull to bit level null onullthe signal stimulating the receivernull This is not possible nullen using real nullSS signals nullr test purposesnull We should loonullupon simulator testing as representing the real nullrld, rather than replicating itnullSpirent simulators include statistical models enabling simulation onullricher multipath environments, but consideration onullthese is outside the scope onullthis documentnull nulligure nullshonull the concept onullsimulation nullsing a nullSnullnull simulatornull Tynullcal GPS Simulators nulll the tests discussed in this nullpplication nullote can be pernullrmed using annullonull Spirentnulls multinullhannel simulatorsnull Simnullnull is the control and scenario denullition sonullnullre nullr nullSnullnull and nullSnullnull series simulatorsnullSimPLEnullis the scenario replanulland control sonullnullre nullr the STR4nullnullsimulatornull nullor nullrther innullrmation on Spirentnulls range onullSimulators, please contact nullour local Spirent representative, or visit nullnullnullpirentnull comnullositioning, or nullnullnullpirentnullom and clicnullthe Satellite nullavigation linnull Fundamental Receinuller Pernullrmance Parameters This nullpplication nullote nullcuses on testing the nullnullparameters to determine a nullSS receivernulls general pernullrmancenull nullnless othernullse stated, nullS LnullCnull code signals are impliednull nulligure null RnullSimulation nulllonull Page nullSPIRENT Application Note Cold Start Time To First Finull TTnull is a measure onullhonullnullicnullnulla receiver pernullrms the signal search processnull The search process, or nullsignal acnullisitionnull has tnull dimensionsnullThe Cnull code dimension associated nullth the replica PRnullcode, and the Doppler dimension associated nullth the carriernullWhen pernullrming the search process a coldnull starting receiver could have a code uncertaintnullonullup to nullnull chips nullhe total number onullcode phase states nullr the nullS Cnull codenull and appronullmatelnullnullnullnullnullnullnullr the Doppler uncertaintnullnullSome receivers use a serial search process, others a parallel nullultinullorrelatornullprocessnull nullaster designs use matched nullter or nullT techninullesnullThe nenullest techninulles use a combined replica onullseveral codes instead onullseparate onesnull null Cold Start TTnull is denulled nulln Renullrence null as the time betnulleen application onullponuller to a receiver and it obtaining the nullst valid navigational data point, nullen the nullllonullng criteria are metnull null Time unnullonull nullCurrent almanac and ephemeris unnullonull nullPosition unnullonull Due to the stochastic nature onullthe process several nullenullrence nullsuggests nullnullTTnull measurements are tanulln nullth dinullnullrent satellite geometries and then averagednull Simulator test nullsing a simulator to pernullrm a Cold Start TTnull test is vernullsimplenull nullirst simulate a static vehicle position nullth satellite ponuller levels set so the ponuller into the receivernulls antenna is nullnull dnullnullWith the scenario running nullnd the receiver connected to the simulatornull ponuller is applied to the receivernull nullnce the receiver has obtained its nullst null, stop the scenario renullnd it nullnullapplicablenulland advance the scenario time bnullat least nullhours to ensure the simulated constellation geometrnullonullvisible satellites has changednullnullternativelnull, change the simulated location bnullseveral thousand null achieves the same enullnullctnull Clear the receiver onullall navigational data and time innullrmation and remove the ponullernull Renullun the modinulld scenario and renullpplnull ponuller to the receivernull Repeat this process the renullired number onulltimes, and average the TTnull resultsnull nullnullnullou are not certain that the receivernulls memornullhas been completelnullerased, nullou can select vernulldinullnullrent locations andnullr times nullears apartnullnullr the scenarionull nulln this nullnull, even inullthe receiver retained some prior navigation innullrmation, it nulluld not be onullusenull Page nullSPIRENT Application Note nullarm Start TTFF null Warm Start TTnull is denulled in Renullrence nullas the time betnulleen application onullponuller to a receiver and it obtaining the nullst valid navigational data point nullen the nullllonullng criteria are metnull nullTime is nullonull nullnullmanac is nullonull null nullo ephemeris nullr the data is more than 4 hours oldnull nullPosition nullthin nullnullm onulllast null Simulator test nullor a simulator test, nullou can use the same scenario as nullr the Cold Start TTnull, as the criteria nulluch as clearing the ephemeris, but not the almanacnullare all set using the receivernull nullnullit is not possible to clear onlnullthe ephemeris, the receiver must nullst be allonulled to collect the almanac nullom the nullll navigation message nullhis tanulls appronullmatelnullnullnull minutesnull nulldvance the scenario time bnull4 hours nullo age the ephemerisnull and set the receiver time to matchnull nullot Start TTFF null nullot Start TTnull is denulled in Renullrence null as the time betnulleen application onullponuller to a receiver and it obtaining the nullst valid navigational data point nullen the nullllonullng criteria are metnull nullTime is nullonull nullnullmanac is nullonull nullEphemeris is nullonull nullPosition nullthin nullnullm onulllast null Simulator test null nullth Warm Start, nullou can use the same scenarionullThere is no clearing onulldata nullom the receiver memornulland no need to stop the scenario in order to alter annull parametersnullPonuller cnullcle the receiver nullr each TTnull testnullnull nullth Warm start, allonull the receiver to collect the nullll navigation message nullppronullmatelnullnullnull minutesnull Page null SPIRENT Application Note Acnullisition sensitinullty nullcnullisition sensitivitnullis the minimum received ponuller level at nullich a nullirst nullinullnull can occurnullThe subnullets onullthis are separate measurements nullr each onullthe cold, nullrm and hot startnullp conditionsnull Simulator test nullor a simulator test, nullou can use a simple static scenarionullThe simulator sonullnullre allonull nullou to control the ponuller level onullthe simulated signal in various nullnull, to a high degree onullresolution, and over a nullde dnullamic rangenull Ponuller control can be in realnullime nullile the scenario is running, or using a prenullcripted set onullcommandsnullRealnullime control can be applied using the Simnullnull nullnullor using remote commands nullnullthe simulator is being controlled bnulla remote snulltemnull nullt is possible to control the ponuller independentlnullon individual satellites, or on all satellites, and level can be displanulled as absolute ponuller, or relative to a renullrencenullThe resolution onullponuller control nullor the nullSnullnull simulatornullis vernullnulle, being nullnullnullover the range nullnull dnull nullnulldnull nullnullnullnullThis allonull accurate determination onulla receivernulls acnullisition sensitivitnullnullnull nullth TTnull, nullou should run several tests nullth dinullnullrent satellite geometries nullnullnulland average the resultsnull Tracnullng sensitinullty Tracnullng sensitivitnullis the minimum ponuller level at nullich a receiver can continue to maintain locnull The tracnullng threshold is closelnullrelated to measurement errors due to error sources in the receivernulls PLL tracnullng loopsnullPhase error, dnullamic stress error and thermal noise are the dominant sources onullerrornull nullinimising these parameters nullll enable the receiver to continue to tracnullsignals at a much lonuller ponullernull nulln all cases, the tracnullng threshold should be lonuller than the acnullisition sensitivitnullnull Simulator test nullor a simulator test, nullou simplnulllonuller the ponuller on all satellite channels simultaneouslnulluntil the receiver loses locnull This should be repeated nullr dinullnullrent satellite combinations and geometries, using the techninulles described in section nullnull Page nullSPIRENT Application Note Reacnullisition Time Reacnullisition time is the time necessarnull nullr a receiver to regain its nullst valid navigational data point anuller total loss onullall received signalsnull nullast reacnullisition time is important nullr innullehicle navigation snulltemsnullConsider a car emerging nullom a tunnel, in nullich it has lost all satellite signalsnullnullmmediatelnull anuller the tunnel is a nullnction at nullich the driver must manull an enulltnullThe navigation snulltem needs to be navigating again nullicnullnullin order nullr it to give the correct nullnullt nullonullnullinstructionnull Simulator test nullor a simulator renullcnullisition time test, ponuller must be reduced on all satellites bnulla minimum onullnull dnull The best nullnull to achieve this is to specinull nullonullnull nullr each satellitenullSimPLEnulland Simnullnull allonull nullou to turn onullnullall satellites nullile the scenario is runningnullWith Simnullnull nullou can also create a prenullenulled nullser nullctionsnull nulle nullich has a timenullrdered list onullcommandsnull nullne such command is nullonuller onnullnullnullnull With SimPLEnull nullou can record realnullime actions and replanullthem nullom a nullenull Set the duration nullr nullich all satellites are onullnullso that the receiver loses complete locnullto ensure a valid reacnullisitionnull Page nullSPIRENT Application Note Static Nanullgation Accuracy Static nullavigation nullccuracnullis the accuracnull to nullich a receiver can determine its position nullth respect to a nullonull locationnull nullt can be split into three categoriesnull Predictable nullThe accuracnullonulla receivernulls position solution nullth respect to the charted solutionnullnullth the position solution and the chart must be based upon the same geodetic datumnull Repeatable nullThe accuracnullnullth nullich a user can return to a position nullose coordinates have been measured at a previous time nullth the same receivernull Relative nullThe accuracnullnullth nullich a user can measure position relative to that onullanother user onullthe same receiver at the same timenull nullt is possible to pernullrm an estimate onull position error nullPEnullnullr a receiver given certain conditionsnull The nullllonullng nullrmula appliesnull EPE nullnulligmanullnullnullnull nullnullRE nullnulligmanull nullnull nullultiplnullng the nullnull nullnullRE nullnullgives EPE nulldrmsnullas given in enullation nullnulland is commonlnulltanulln as the nullnulllimit nullr the magnitude onullthe horinullontal errornull The probabilitnullonullhorinullontal error is nullthin an ellipse onullradius nullrms ranges betnulleen nullnull and nullnull depending on the ratio onullthe ellipse seminullnullesnull EPE nulldrmsnullnullnullnullnullnull nullSQRT nullREnullnullnullEnull nullnull nullnull, nullnull, PDnull and nullnull are determined bnullthe geometrnullonullthe current satellites visible above the receivernulls masnullangle nullth respect to user receivernulls antennanullDnulls can be degraded nullade largernullbnullsignal obstruction due to terrain, nullliage, building, vehicle structure, and so onnull nullE is an estimate onullnullignals in Spacenull errors, such as ephemeris data, satellite clocnull, ionospheric delanulland tropospheric delanullnullThese errors can be greatlnullreduced bnulldinullnullrential and multiple nullenullencnulltechninullesnullDinullnullrential correction sources include user provided renullrence stations, communitnullbase stations, governmental beacon transmissions, null subnullarrier transmissions and geosnullchronous satellite transmissionsnull Page nullSPIRENT Application Note Table null LnullCnull nullser Enullivalent Range Error nullEREnull nullE includes receiver noise, multipath, antenna orientation, EnullnullnullnullReceiver and antenna design can greatlnullreduce nullE error sourcesnull Position error can range nullom tens onull metres nullecreational applicationsnullto a nullnull millimetres nullurvenullapplicationsnulldepending on enullipment, signals and usagenull Pronullssional mapping and survenull enullipment onullen includes usernullettable minimum thresholds nullr parameters such as Snull, masnullangle, Dnull, number onullSnull used, etcnull nullRE is nullser Enullivalent Range Error, and is computed nullor LnullCnullnullas shonull in Table null Simulator test nullor a simulator test, nullou can eliminate nullRE and certain nullE errors bnulldisabling the enullnullcts onullthe atmosphere, and deliberatelnullnot including annull ephemeris, clocnullerrors, multipath or Enullnull Rnull in the simulationnullThis is not possible using real satellite signalsnullnullor this reason, it is not possible to phnullicallnullmeasure a receivernulls absolute navigation accuracnull nullth annullmethod other than using a nullSS simulatornull To measure Static nullavigation nullccuracnullnullou denulle a scenario, nullth a static position null nulldegrees Latitude, nulldegrees Longitude and nullmetres height is alnullnull a good location as it is easnullto see annulldivergence that nullll be highlighted in nonnullero digitsnull The scenario should run nullr at least null hours nulls stated in Renullrence null and the ponuller level must not enullceed nullnull dnull nullhe Received nullinimum RnullSignal Strength as denulled in Renullrence nullnull Some receivers have a mode that nulles the position inullthe detected velocitnull nulllls belonulla certain thresholdnull This sonullalled nullstatic modenull is usenulll nullr innullar receivers, to prevent displanullnullitternull nullen the vehicle is stationarnullnullnullonullever, nullen pernullrming a static position accuracnull test, this mode must be disabled to prevent a nulllselnullgood resultnull Renullrence 4 gives a detailed enulllanation onullhonullto measure accuracnullpernullrmancenull Error source nullias Random Total DnullS Ephemeris Data nullnull nullnull nullnull nullnull Satellite Clocnull nullnull null7 nullnull nullnull nullonosphere 4null nullnull 4null null4 Troposphere nullnull nullnull null7 nullnull nullultipath nullnull nullnull null4 null4 Receiver measurement nullnull nullnull nullnull nullnull nullRE nullnulligma Rnullnull nullnull null4 nullnull nullnull nulliltered nullRE, Rnull nullnull null4 nullnull nullnull nullertical nullsigma errors nullnullnull nullnullnull nullnull nullnull nullorinullontal mnullsigma errors nullDnullnullnullnull nullnull nullnull Page nullSPIRENT Application Note nullnamic Nanullgation Accuracy Dnullamic nullavigation nullccuracnullis the same as Static nullavigation nullccuracnull, enullcept the receiver is undergoing motion in either or all onullthe three anulles onullmovement null null, null Simulator test nullor a simulator test, denulle a scenario nullth a simple tranullctornulldenulled using Simnullnullnulls internal vehicle model commandsnullTo ensure data denullorrelation, run the test over a minimum onullthree time periods onullduration no less than one hour eachnullEach period must contain at least nullnull valid navigation data pointsnull The three tests should be enullallnull spaced during a nullnullour periodnull nullor application specinull dnullamic accuracnull pernullrmance, a simulator can pernullrm almost annulldnullamic tranullctornullpronulle nullou desirenullThe high dnullamic pernullrmance onullSpirentnulls simulators enables testing onullreceivers nullr annullapplication nullere dnullamic motion is renullired, nullom emergencnullbeacons drinulling in the sea, to militarnullordnance shells spinning at several hundred revolutions per secondnull Page nullSPIRENT Application Note Radio Frenullency Internullrence Rnull is denulled as annullunnullnted signal that causes degradation in pernullrmance, partial loss, or nullll loss onullnavigationnull Such signals are onullen renullrred to as nullammingnull signalsnullnullamming, being a nulldelnull used term describing a signal that prevents the nullnted radio communication nullom being receivednull nullamming can either be intentional or unnullntentionalnullnullntentional nullamming is a result onulla deliberate attempt to dennull a nullSS receiver use onullthe nullSS snulltemnull null enullmple manullbe nullund nullthin the theatre onullnullr, nullere an enemnullis trnullng to attacnullthe othernulls capabilitnullnull null advanced nullrm onullintentional nullmming, called nullpoonullgnull involves renullransmission onullnullSSnullinull signals that manull a receiver thinnullit is navigating in a nullnullnullich, in realitnullit is notnull nullnnullntentional nullmming results nullom unnullonull internullrencenullnullt is less specinull, and can come nullom a nullde varietnullonull sourcesnull Enullmples includenullharmonics nullom commercial Tnullbroadcast stations or pulsed internullrence nullom nullrcranull nullnullnullnull navigation beaconsnull The main vulnerabilitnullonullnullSS signals nullth respect to both tnulles onullnullmming is that thenullare enullremelnulllonullponuller nullen arriving at the receivernulls antenna nullnullicallnullnullnull dnullnull The signals are, in nullct some null dnullbelonullthe level onullbacnullround noise, necessitating the use onullsignal processing gain nullorrelatorsnullin the receiver to enullract the signal nullom the noisenull To emphasise the vulnerabilitnullonull a receiver to nullmming, it is estimated that an airborne nullnulltt CW nullmmer signal on the Lnullnullenullencnullnullnull7nullnullnullnullcan dennull nullS tracnullng to an alreadnulllocnulld receiver at up to nullnull anullnull, and prevent an unnullocnulld receiver acnulliring locnullat up to nullnull anullnullnullRenullrence nulldiscusses this in detailnull Simulator test nullor a simulator test, there are several optionsnullSimple nonnulloherent nullmming is easilnullachieved nullth Spirentnulls nullSnullnull and nullSnullnull series onullsimulators, as thenull have an Rnullnullammernull input port that allonull nullou to innullct an enullernal Rnullsignal into the main nullSS signal path in a controlled nullnullnullsing a directional coupler nullthin the simulatornull nulligure nullshonull this conceptnull nulligure null Tnullical nullnternullrence Simulation Setnullp Page nullSPIRENT Application Note null signal innullcted nullom a thirdnullartnull signal generator nulluld not be coherent nullth the simulators nullSS signalnull nullonullever, the Spirent nullS77null nullnternullrence Simulation Snulltem option is available nullr nullSnullnull and nullSnullnull series simulatorsnull This allonull specinull signal generators to be controlled using Simnullnull in either a coherent or nonnulloherent nullnullnullth a varietnullonullsignal modulation tnulles and nullth modelled ponuller, nullich simulates the relative distance enullnullcts onullthe internullrence source nullth respect to the simulated nullSS position nullor enullmple, a nullmming source nulling over a receivernulls locationnull nullor more innullrmation regarding the nullS77null internullrence simulation option, see Renullrence null Page nullSPIRENT Application Note Conclusions This nullpplication nullote describes the nullndamental pernullrmance parameters that applnullto all nullSS receiversnull These parameters must be optimised at an earlnullstage in a receiver designnull nullptimisation renullires suitable testingnull This nullpplication nullote shonull that a nullSS simulator allonull nullou to develop tests that optimise receiver designnullSimnullnull onullnullrs vernullhigh resolution control onullsignals and bitnullevel manipulation onulldata, reproducing the most complenullerror enullnullcts nullile its easnulltonullse internullce allonull straightnullrnullrd tests to be carried out nullth the same ponullernulll modelling tanullng place in the bacnullroundnull nullt shonull that there are no practical alternatives to simulator testing in situations nullere the receiver must be tested nullile undergoing highnullnullamic motionnull Renullrenced nullocuments null nullnullSTD nullnullRecommended Test Procedures nullor nullS Receivers, nullnullnullnull null nullnullPSnullnullD nullavstar nullS Space Segmentnullavigation nullser nullnternullce Specinullation, Revision D, 7th Dec nullnull null nullDnullPSnullnull nullavstar nullS Space Segmentnullavigation nullser nullnternullce Control Document, Revision nullnull nullnullnullnull, nullth nullpril nullnull 4null nullS SPS Signal Specinullation, nullnenullC, nulleans onullmeasuring nullS pernullrmance null nullulnerabilitnullassessment onullthe transportation innullastructure replnullng on the nulllobal Positioning Snulltem nullnullohn null nullolpe, nullSC, nullug nullth, nullnullnull null nullnullnull nullS77null nullnternullrence Simulation Snulltem Product Specinullationnull 7null Dnullnullnullnullnull Latest nullssue SimPLEnull Standard Scenario Descriptions Page nullSPIRENT Application Note Glossary onullTerms Cnull Code The nullS SPS Coarse nullcnullisition ranging code Chip The time betnulleen transitions in the Cnull code nullot renullrred to as a nullitnull because the code does not carrnullinnullrmationnull Dnull Dilution onullPrecision nullDnull nullnulleometric Dnull, nullnull nullnullorinullontal Dnull, nullnull nullnullertical Dnull, PDnull nullPosition Dnull, TDnull nullTime Dnull Enull Electronullagnetic nullnternullrence EPE Estimated Position Error nullT nullast nullourier Transnullrm nullSS nulllobal nullavigation Satellite Snulltem nullnullor enullmplenullnullS, nulllonass null nullalileo PPS nullS Precise Positioning Service, emplonullng PRnull Pseudonullandom nullumber codenullnull code nullich appears completelnull random nullen a portion onullit is vienulled, but nullich in realitnullrepeats nullor the nullS Cnull code the repetition is nullS, the nullS Pnullode tanulls 7 danull to repeatnull Rnull Radio nullrenullencnull Rnull Radio nullrenullencnullnullnternullrence Scenario nulln this contenull, a nullSS simulation running on either Simnullnull or SimPLEnullsimulator control sonullnullrenull Snull Signalnullonulloise Ratio SPS nullS Standard Positioning Service, emplonullng the Cnullnullode Snull nullS Satellite nullehicle TTnull Time To nullirst nullinull nullE nullser Estimated Error nullRE nullser Estimated Range Error nullalid nullavigational Data Point null single, timenullagged estimate nullnullnull onullLatitude, Longitude and nulltitude renullrenced to the Wnullnull4 nullor nullSnullcoordinate snulltem, computed nullile in null navigation mode nullnullnullnull nullnullnullmninullirectional Rangenullistance nulleasuring Enullipment Page nullSPIRENT Application Note Page nullSPIRENT Application Note CONTACT null Snullrent Communications null4 nullnull nullnullnull globalsalesnullpirentnullom nullnullnullpirentnullomnullositioning Snullrent Federal Systems null 7null nullnullnullnull innullnullpirentnullderalnullom nullnullnullpirentnullderalnullom nully not snullre tnulls documentnull Got a smartnullonenull If you have a smartphone download a QR Code reader and then point your phone camera at the QR Code to read the graphic. DnullnullnullnullSnull nullnull nullaceboonull Linnulldnulln Tnulltter Technorati nulloogle nullunull Digg Delicious Reddit Stumbleupon Revnullnullnullnullul nullnull nulle are adding nenullcontent to our nullenullite on a regular nullsisnull nullonullarnulltnulls linnull nullnullnullpirentnullomnullositioning nullisit tnull Snullrent GNSS nullognulltnullre are currently onuller null nullsts nulltnull2 to 3 nenullnullsts added eacnullnulleenull Catcnullunullon nullatnulls nenullnull nullnullnullpirentnullomnulllognullositioningnullspnull Need more innullrmationnull gnssnullolutionsnullpirentnullom