Patent ID: 11885890
Assignee: U-BLOX AG
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 3:
4. A computer-implemented method for global navigation satellite system (GNSS) measurements, the method comprising:
specifying, in advance, a prior probability density P(x) of a state x;
specifying, in advance, a system model h(x) that relates the state x to observables z of the measurements;
quantifying, during the measurements, quality metrics q associated with the measurements;
specifying, in advance, a non-Gaussian residual error probability density model ƒ(r|θ, q) and fitting model parameters θ determined off-line a priori, where r is a residual error;
defining, during the measurements, a posterior probability density P(x|z, q, θ);
estimating, during the measurements, the state x; and
computing, during the measurements, a protection level of a position estimate by integrating the posterior probability density P(x|z, q, θ) over the state x,
wherein the non-Gaussian residual error probability density model is a student-t distribution function, and specifying the residual error probability density model ƒ(r|θ, q) further comprises:
identifying a model for a pseudorange using the student-t distribution function as:, f
    pr
   
   (
   r
   )
  
  =
  
   
    
     Γ
     ⁡
     (
     
      
       v
       +
       1
      
      2
     
     )
    
    
     
      
       v
       ⁢
       π
       ⁢
       
        σ
        2
       
      
     
     ⁢
     
      Γ
      ⁡
      (
      
       v
       2
      
      )
     
    
   
   ⁢
   
    
     (
     
      1
      +
      
       
        r
        2
       
       
        
         σ
         2
        
        ⁢
        v
       
      
     
     )
    
    
     -
     
      
       v
       +
       1
      
      2
     
    
   
  
 

where r is the residual error, ν is a degrees of freedom parameter, σ is a scaling parameter, and Γ is the gamma function.