ARAIM availability prediction method under complex terrain environment

Patent metadata

Field	Value
Publication number	US-12461252-B2
Application number	US-202318138156-A
Country	US
Kind code	B2
Filing date	Apr 24, 2023
Priority date	Dec 5, 2022
Publication date	Nov 4, 2025
Grant date	Nov 4, 2025

Abstract

An ARAIM availability prediction method under a complex terrain environment is provided. The method includes: 1) selecting positioning points according to an air line; 2) calculating terrain shielding angles; 3) predicting visible satellites; 4) determining a fault mode that needs to be monitored; 5) calculating a positioning error variance, an influence coefficient of a nominal deviation, and a variance of a solution separation test statistic; and 6) calculating a threshold of a solution separation test, calculating a protection level, and determining availability. According to the method, the terrain shielding angles are calculated based on terrain model data, and the visible satellites are predicted based on ephemeris data or almanac data to further calculate a protection level, while determining the availability; and the accuracy of availability prediction can, by considering the effect of terrain barriers on the prediction of the visible satellites, be improved to ensure the safety of aircrafts.

First claim

What is claimed is:

1 . An advanced receiver autonomous integrity monitor (ARAIM) availability prediction method under a complex terrain environment performed by a processor, comprising the steps of:
1) selecting a positioning point according to an air line of an aircraft under operation; 2) calculating terrain shielding angles; 3) predicting visible satellites; 4) determining a fault mode, wherein the fault mode needs to be monitored; 5) calculating a positioning error variance, an influence coefficient of a nominal deviation, and a variance of a solution separation test statistic; 6) calculating a threshold of a solution separation test, calculating a protection level, and determining an availability; and 7) sending safety warnings to the aircraft based on the determined availability.

2 . The ARAIM availability prediction method according to claim 1 , wherein the terrain shielding angles are based on all directions of terrain model data, with a calculation method of the terrain shielding angles comprising: determining a step size in search of directional angles, and calculating the terrain shielding angle of each of the directional angles with the terrain model data.

3 . The ARAIM availability prediction method according to claim 2 , wherein a selection range of the terrain model data is set in a way that the terrain model data of a circle centered on a user positioning point A or a square area is selected, with a diameter or a side length greater than or equal to 50 km over a search range.

4 . The ARAIM availability prediction method according to claim 3 , wherein a search method of a maximum elevation positioning point based on the terrain model data comprises the following steps of
setting an azimuth angle as theta, searching a pixel block of the directional angle between a center point and the user positioning point A within [θ AB −β/2, θ AB +β/2] based on the step size (beta) in search of the directional angle, calculating an elevation between a center point of the pixel block and the user positioning point, and searching a maximum elevation; and selecting the terrain shielding angle corresponding to the azimuth angle theta, wherein the azimuth angle theta is equivalent to the maximum elevation.

5 . The ARAIM availability prediction method according to claim 4 , wherein a calculation method of the elevation based on the terrain model data is as follows:
the user positioning point A and a user positioning point B are set as sampling center points of the terrain model data, and the elevation between any one point in a sampling pixel block of the terrain model data, centered on the user positioning point B, and the user positioning point A is calculated in the following formula:

α
AB

=

max
⁡
(

arcsin
⁡
(

n
→

A

·

AB
→



AB
→



)

,
0

)

.

6 . The ARAIM availability prediction method according to claim 2 , wherein the step size in search of the directional angles, in the calculation method of the terrain shielding angles, is set in a way that the directional angles in search are distributed uniformly, and the step size in search is less than or equal to pi/180.

7 . The ARAIM availability prediction method according to claim 1 , wherein a prediction method of the visible satellites considering a terrain influence is as follows:
calculating satellite positions according to an ephemeris or almanacs of the satellites, and filtering out satellites with the elevations being less than the terrain shielding angle and a receiver shielding angle, and obtaining a predicted visible satellite set; a screening rule is as follows: a directional angle of a satellite C, observed by a user receiver, is denoted as θ AC , the elevation is denoted as α AC , the terrain shielding angle corresponding to the directional angle is denoted as α AB , and the receiver shielding angle corresponding to the directional angle is denoted as α rc ; and if the satellite C satisfies

θ
AC

∈

[

θ
AB

-

β
2

,

θ
AB

+

β
2

)

,

α
AC

>

max
⁡
(

α
AB

,

α
rc

)

,

the satellite C is viewed as a visible satellite, or else, the satellite C is invisible.

8 . The ARAIM availability prediction method according to claim 1 , wherein a selection method of monitored fault modes for an ARAIM considering a terrain influence is as follows:
calculating the terrain shielding angles corresponding to all-directional angles with terrain model data, predicting to obtain a visible satellite set, calculating fault probabilities in different fault modes according to a primary service fault probability of a single satellite and primary service fault probabilities of at least two satellites in an integrity support message (ISM), and selecting a larger fault mode therefrom as the monitored fault mode in a principle that a total probability of fault modes to be monitored should not exceed a preset value.

9 . The ARAIM availability prediction method according to claim 1 , wherein an ARAIM continuity risk method considering a terrain influence is as follows:
calculating the terrain shield

Assignees

• Univ Beihang

Inventors

• Zhu Yanbo
• Wang Zhipeng
• Fang Kun
• Du Jingtian
• Wang Hongxia

Classifications

• G01S19/40 Primary

  Correcting position, velocity or attitude · CPC title

• G01S19/20 Primary

  Integrity monitoring, fault detection or fault isolation of space segment · CPC title