LAAS ground facility sigma monitor

• US 7,019,688 B1
• Filed: 03/24/2005
• Issued: 03/28/2006
• Est. Priority Date: 03/24/2005
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Reuter, Randy J., Brenner, Mats
• Primary Examiner(s): PHAN, DAO LINDA
• Application Number:
  US11/089,156
• Time in Patent Office: 369 Days
• Field of Search: 342/34, 342/37, 342/173, 342/357.02, 342/357.03, 342/357.06, 701/207, 701/213
• US Class Current: 342/357.29
• CPC Class Codes: G01S 19/071 DGPS corrections
• CPC Class Codes: G01S 19/08 providing integrity information, e.g. health of satellites or quality of ephemeris data

Abstract

A 1-sigma pseudorange ground monitor (sigma monitor) is described. The sigma monitor calculates a weighted sum of squared deviations referred to as the discriminator for one or several reference receiver for a specific time period. The sigma monitor also calculates an alert threshold based on the chi-square or near chi-square probability distributions for one or several reference receivers and for the specific time period. The sigma monitor then compares the discriminator with the alert or alarm threshold. If the discriminator is greater than the alert or alarm threshold, an alert or alarm is issued and logged.

Claims

1. A method of monitoring 1-sigma pseudorange ground (sigma_pr_gnd) values, comprising in combination:

calculating deviations from differential correction data;

normalizing the deviations with an expected deviation 1-sigma value;

calculating a discriminator as a weighted sum of squared normalized deviations for at least one reference receiver over a time period;

calculating a near chi-squared alert threshold for the at least one reference receiver for the time period;

comparing the discriminator with the near chi-squared alert threshold; and

issuing an alert if the discriminator is greater than the near chi-squared alert threshold.

2. The method of claim 1, wherein the deviations are calculated from differential correction data that is carrier smoothed.

3. The method of claim 1, wherein the deviations are calculated from differential correction data that is not carrier smoothed.

4. The method of claim 1, wherein the deviations are normalized by dividing the deviations with the expected deviation 1-sigma value.

5. The method of claim 1, wherein the expected deviation 1-sigma value is calculated as follows:

$\mathrm{\sigma <br><br>}<br><br><br><br>{\mathrm{dev}}_{\mathrm{sv}}^i=\sqrt{{\left(\frac{\left(M-1\right)<br><br>{\mathrm{\sigma <br><br>}}_{c^i<br><br>\mathrm{sv}}}{M}\right)}^2+\underset{m=1,m\ne <br><br>i}{\overset{M}{\sum <br><br>}}<br><br>{\left(\frac{{\mathrm{\sigma <br><br>}}_{c^m<br><br>\mathrm{sv}}}{M}\right)}^2}.$

6. The method of claim 1, wherein the discriminator combines differential correction data from all available satellites over all available azimuths and elevations for the at least one reference receiver.

7. The method of claim 1, wherein the discriminator for the at least one reference receiver and the time period is calculated as follows:

$d^i<br><br>\left(q\right)=\frac{\underset{k=1}{\overset{K<br><br>\left(q\right)<br><br>\left(i\right)}{\sum <br><br>}}<br><br>{\mathrm{SNDEV2}}^i<br><br>\left(q\right)<br><br>\left(k\right)}{\underset{k=1}{\overset{K<br><br>\left(q\right)<br><br>\left(i\right)}{\sum <br><br>}}<br><br>N<br><br>\left(k\right)}.$

8. The method of claim 1, wherein the discriminator for the at least one reference receiver and the time period is calculated as follows:

$d<br><br>\left(q\right)=\frac{\underset{i=1}{\overset{M}{\sum <br><br>}}<br><br>d^i<br><br>\left(q\right)}{M}.$

9. The method of claim 1, wherein the time period is less than a two and a half minute interval.

10. The method of claim 1, wherein the near chi-squared alert threshold is calculated as follows:

$T_{\mathrm{\alpha <br><br>}}^v=\underset{k=0}{\overset{\mathrm{Kord}}{\sum <br><br>}}<br><br>{\mathrm{coef}}_{\mathrm{\alpha <br><br>}}<br><br>\left(k\right)·<br><br>v^k.$

11. The method of claim 1, wherein the alert includes an identification of the at least one reference receiver and the time period.

12. The method of claim 1, further comprising calculating a near chi-squared alarm threshold and issuing an alarm if the discriminator is greater than the alarm threshold.

13. The method of claim 1, further comprising excluding the at least one reference receiver.

14. A system for monitoring 1-sigma pseudo range ground (sigma_pr_gnd) values, comprising in combination

a processor;

data storage; and

machine language instructions stored in the data storage executable by the processor to;

calculate deviations from differential correction data;

normalize the deviations with an expected deviation 1-sigma value;

calculate a discriminator as a weighted sum of squared normalized deviations for at least one reference receiver over a time period;

calculate a near chi-squared alert threshold for the at least one reference receiver for the time period;

compare the discriminator with the near chi-squared alert threshold; and

issue an alert if the discriminator is greater than the alert threshold.

15. The system of claim 14, wherein the deviations are calculated from differential correction data that is carrier smoothed.

16. The system of claim 14, wherein the deviations are calculated from differential correction data that is not carrier smoothed.

17. The system of claim 14, wherein the deviations are normalized by dividing the deviations with the expected deviation 1-sigma value.

18. The system of claim 14, wherein the expected deviation 1-sigma value is calculated as follows:

$\mathrm{\sigma <br><br>}<br><br><br><br>{\mathrm{dev}}_{\mathrm{sv}}^i=\sqrt{{\left(\frac{\left(M-1\right)<br><br>{\mathrm{\sigma <br><br>}}_{c^i<br><br>\mathrm{sv}}}{M}\right)}^2+\underset{m=1,m\ne <br><br>i}{\overset{M}{\sum <br><br>}}<br><br>{\left(\frac{{\mathrm{\sigma <br><br>}}_{c^m<br><br>\mathrm{sv}}}{M}\right)}^2}.$

19. The system of claim 14, wherein the discriminator combines differential correction data from all available satellites over all available azimuths and elevations for the at least one reference receiver.

20. The system of claim 14, wherein the discriminator for the at least one reference receiver and the time period is calculated as follows:

$d^i<br><br>\left(q\right)=\frac{\underset{k=1}{\overset{K<br><br>\left(q\right)<br><br>\left(i\right)}{\sum <br><br>}}<br><br>{\mathrm{SNDEV2}}^i<br><br>\left(q\right)<br><br>\left(k\right)}{\underset{k=1}{\overset{K<br><br>\left(q\right)<br><br>\left(i\right)}{\sum <br><br>}}<br><br>N<br><br>\left(k\right)}.$

21. The system of claim 14, wherein the discriminator for the at least one reference receiver and time period is calculated as follows:

$d<br><br>\left(q\right)=\frac{\underset{i=1}{\overset{M}{\sum <br><br>}}<br><br>d^i<br><br>\left(q\right)}{M}.$

22. The system of claim 14, wherein the time period is less than a two and a half minute interval.

23. The system of claim 14, wherein the weighted near chi-squared alert threshold is calculated as follows:

$T_{\mathrm{\alpha <br><br>}}^v=\underset{k=0}{\overset{\mathrm{Kord}}{\sum <br><br>}}<br><br>{\mathrm{coef}}_{\mathrm{\alpha <br><br>}}<br><br>\left(k\right)·<br><br>v^k.$

24. The system of claim 14, wherein the alert includes an identification of the at least one reference receiver and the time period.

25. The system of claim 14, further comprising machine language instructions to calculate a near chi-squared alarm threshold and issue an alarm if the discriminator is greater than the alarm threshold.

26. The system of claim 14, further comprising machine language instructions to exclude the at least one reference receiver.