Customer Service Center

• PosApp (SimGEN / SimREPLAYplus / SimREPLAY)

• The vehicle personality file limits are very much unchanged since the early designs of the Spirent's GPS simulator
  • When simulations were run at a mere 10Hz    (1kHz is the modern-day Spirent simulator capability!)
  • Simulation data had to be pre-processed and as such the amount of data generated had to be kept to a minimum
• However the limits were also adopted in order to reflect real-world dynamic limits of a typical fighter aircraft
  • Such as the Harrier (a common fighter plane at that time) 
• This was based, in part, on the paper* by S J Gale provided an analysis of Roll rates, Lever Arm and Simulation update rate and minimisation of errors.
• The Dynamic Limits proposed at the time were:
  • Velocity: 100,000 ms^-1
  • Acceleration: 150 ms^-2
  • Jerk:  500 ms^-3
  • Roll rate: 6.3 rads^-1  (1.5m lever arm)
• Here then is where the personality file limit of 7ms^-1 was established
   
• Compare with Spirent's current simulator dynamic limits (GSS8000 / GSS9000):
  • Velocity: 120,000 ms^-1
  • Acceleration: 192,600 ms^-2
  • Jerk:  890,400 ms^-3
  • Roll rate: 60pi rads^-1  (1.5m lever arm)
• Of course, the RF dynamic limits account for more than just the motion of the vehicle
  • The RF signal changes are a reflection of the total modelled simulation environment - vehicle, satellites, atmosphere, undeclared errors, etc.

*   Reference: GPS Simulator, by S J Gale, STL Harlow, 23rd Sept 1985