JP2001143200A - Satellite navigation receiving system and monitoring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To settle a problem such that an airplane may possibly be unable to detect its abnormality when a rather low protecting level is calculated compared with the actual level due to the abnormality of a ground device despite a fact that the airplane gets out of its prescribed flying course. SOLUTION: A function is provided independently of a conventional integrity monitoring function to search for the obstacles while varying the gain of a transmitter 18 in energy flying phase of an airplane. In other words, the radio waves are radiated from the transmitter 18 via an antenna 110 within a range set on a bubble having the horizontal/vertical alarm limits defined as its covering area. Then the reflected radio waves are received by a receiver 111 and a signal processing part 112 detects the disturbance of these reflected waves. Thus, the obstacles existing near an actual flying course can be detected. In such a constitution, the integrity monitoring results are integrated by an alarm decision part 114 according to the conventional protecting level and an alarm is generated with higher reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a satellite navigation receiving system and a monitoring device, and more particularly, to a global navigation navigation system (GNSS) using artificial satellites.
The present invention relates to a satellite navigation receiving system called a "tellite system" and a monitoring device.

[0002]

2. Description of the Related Art Conventional global satellite navigation systems (GN)
SS), a satellite-based wide area augmentation system (SB)
A description will be given by taking AS (Satellite Based Augmentation System) as an example. The navigation satellite referred to in this specification is a global positioning system (GPS).
System satellites) (hereinafter, referred to as GPS satellites) have been published by the Japan Society of Surveyors “Basics of GPS surveying” and many others, and are publicly known, and therefore description thereof is omitted. Hereinafter, the prior art will be described in the order of (1) Overview of SBAS, (2) Processing of integrity information in a receiving system, and (3) Other related art related to integrity.

(1) Outline of SBAS FIG. 6 shows an overall system diagram of an example of the SBAS. In the figure, monitoring stations 61 to 64 on the ground are GPS satellites 601.
, And sends the processed data to the navigation control station 66 via the GNSS network 67. The navigation control station 66 has the
It processes the information from 64 and sends an uplink signal 68 to the geostationary satellite 605. The geostationary satellite 605 converts the carrier signal to a predetermined frequency, radiates the SBAS signal 69 over a wide area, and transmits a downlink signal 68 to the navigation control station 66. The SBAS signal 69 can be roughly divided into the following three services for the user (mainly assuming the aircraft 605): a. GPS-like signal, b. Differential correction information, c. Provide integrity information respectively.

A. Provision of GPS-like signal The navigation control station 66 converts the transmitted signal into a predetermined pseudo-random code (Psuedo Ran
dom Noise Code (hereinafter referred to as PRN code). When this is transmitted via the geostationary satellite 605,
This signal is SBAS equivalent to GPS satellites 601 to 604
The signal 69 will be provided to the user, the aircraft 605. Since the GPS satellites 601 to 604 are orbiting satellites, their arrangement changes with time, and this change in arrangement affects the positioning error.
By transmitting the AS signal 69, a source that always provides a stable signal from the same position is obtained, and the reliability of the system is improved.

B. Provision of differential correction information GPS has various error factors. Among them, an error caused by a satellite is a common error factor in a receiver that receives a signal from the same satellite. The errors caused by the satellite include, for example, an error that changes relatively fast, such as a clock error of the satellite, and an error that changes relatively slowly, such as the position of the satellite (ephemeris). This error is
A correction term is extracted from the GPS data received by the monitoring stations 61 to 64 on the ground of the BAS, and is superimposed on the previous GPS-like signal as separate messages (Fast Correction and Long Term Correction). The user (aircraft 605) can use this to correct the pseudorange obtained by positioning with its own receiver, thereby allowing the user to perform more accurate positioning.

C. Provision of Integrity Information By transmitting correction values from the monitoring stations 61 to 64 on the ground via the geostationary satellite 605, positioning accuracy is improved, but errors are not eliminated. The navigation control station 66 calculates the correction value, and at the same time, estimates the residual error of the range domain after the user (aircraft 605) performs the differential correction, and notifies the user (aircraft 605) of the error with another message. Have a function. In this sense,
This parameter is UDRE (User Differential Range
Error).

[0007] UDRE is a GPS satellite 601-60
4 is individually calculated, and when it exceeds a predetermined value, it also has the role of a flag that prohibits the use of the GPS satellite. That is, the error of the corrected error is constantly monitored, and if an error is detected, the user (aircraft 605) is notified in a timely manner, so that the user (aircraft 605) uses the data of the GPS satellite in which the error has occurred. It is possible to avoid the possibility of an accident due to the accident. A message having such a function is called integrity information.

(2) Processing of Integrity Information in Receiving System As described above, the navigation control station 66 on the ground can perform processing relating to errors caused by the GPS satellites 601 to 604, but errors not caused by the GPS satellites 601 to 604. Factors,
For example, the clock error and the tropospheric error of the user receiver are calculated by the user receiver based on a predetermined algorithm. By integrating these residual errors and multiplying them by a predetermined coefficient (referred to as K value), a parameter called a protection level is obtained. The protection level has both horizontal and vertical components, and is divided into a horizontal protection level and a vertical protection level.

For example, taking the vertical protection level as an example, K
A value of 6.33 is used. This is 1-10-7 when the integrated error distribution is regarded as a Gaussian distribution.
Indicates a region included with the probability of. In other words, the user (aircraft 605) receives 1-10- from both the information received from the navigation control station 66 and the information obtained by self-confidence.
It is possible to calculate the protected level with a probability of 7. Even if some trouble relating to the positioning of the user (aircraft 605) occurs, the protection level increases as the residual error increases. When this exceeds the preset alarm limit, the user (aircraft 6)
05) can detect an abnormality and prevent an accident before it occurs.

FIG. 7 is a block diagram showing an example of the integrity monitoring. The algorithm of the user receiver is described in Reference 1 (RTCA Do-220A Minimum Operational Performan).
ce Standard for Global Positioning System / Wide Are
a Augmentation System Airborne Equipment).

The receiver processing unit 70 of the user shown in FIG.
The UDRE information 11 is received and input from a navigation control station on the ground via a geostationary satellite. In addition, the navigation control station also transmits an ionospheric vertical delay error for each grid point (grid point) when the ground is cut by a mesh of a predetermined width. This is usually called GIVE (Grid Ionospheric Vertical Error), and is indicated by GIVE information 13 in FIG. In addition, as shown by 12 in FIG. 7, parameters (factors) of other error factors are also transmitted from the ground via a geostationary satellite.

These parameters transmitted from the ground 1
The receiver processing unit 70 for calculating the above-described protection level from the parameters 1 to 13 and the on-machine parameters includes a calculation processing unit 71
And 72, an integrated processing unit 75 for the dispersion value σ2 of all satellites, and a protection level calculation processing unit 76. The calculation processing unit 71 is a processing unit for calculating the variance of the residual error after performing the short-term and long-term correction. The calculation processing unit 72 uses the GI
A calculation processing unit that estimates an ionospheric error at a user position based on the VE information 13. On the other hand, the variance σ of all satellites
The integration processing unit 75 integrates the errors such as the variance value 73 of the receiver error and the variance value 74 of the tropospheric error, and multiplies the K value by the protection level calculation processing unit 76.
The horizontal protection level and the vertical protection level are calculated.

Next, the relationship between the positioning data protection level and the alarm limit in the user receiver will be described with reference to FIG. 2 using an example of the relationship between the vertical accuracy and the vertical protection level alarm limit. Vertical accuracy 21 shown in FIG.
Is shown on the assumption that the true value is known because the user cannot know the true position. Therefore, the degree to which the user applies the correction value and trusts the result of the positioning depends on the reliability of the protection level calculated as described above. In FIG. 2, a broken line 22 indicates a change in the protection level over time. If the value of this protection level is within the range of the alarm limit 23,
That is, it is considered that the user is within the allowable range with a probability of 1-10-7. An arrow 24 indicates a state where the protection level exceeds the alarm limit 23.

As described above, the integrity monitoring function of the conventional satellite navigation receiving system receives parameters integrated and processed by the navigation control station on the ground, calculates the protection level using the parameters, and uses the parameters to calculate the protection level. This is a method of detecting an abnormality by comparison.

[0015]

However, the above conventional satellite navigation receiving system has a problem that integrity monitoring is passive. That is, in the related art, integrity monitoring is performed on the assumption that the parameters are derived on the ground station side and are correct. Therefore, if some abnormality occurs and the UDRE value is actually extremely large, but the ground side transmits a small UDRE value, and the protection level is calculated to be smaller than the actual value, Aircraft 6 as a user
05 is a risk factor.

Further, due to the occurrence of some abnormality, the aircraft 6
If the flight course of 05 deviates from the predetermined course, the position error is large, but the protection level may be small. This situation is shown in FIG. In the figure,
The solid line 31 indicates the vertical accuracy, the broken line 32 indicates the vertical protection level, and the dotted line 33 indicates the alarm limit. Here, the vertical precision 31
In the portion indicated by 34, the relationship between the vertical protection level and the accuracy is reversed. In this case, the aircraft 60 as the user
No. 5 does not know the actual error, sees the vertical protection level 32 to determine that there is no problem, and does not detect an alarm.
This suggests that the system may not be able to detect anomalies even if the aircraft 605 is approaching an obstacle.

The present invention has been made in view of the above points,
It is an object of the present invention to provide a satellite navigation receiving system and a monitoring device capable of actively detecting an alarm even when a user cannot detect an abnormality and the protection level becomes lower than an actual error.

Another object of the present invention is to provide a satellite navigation receiving system capable of improving reliability by actively monitoring the integrity of position information passively provided on the user side. A monitoring device is provided.

[0019]

In order to achieve the above object, a satellite navigation receiving system according to the present invention provides processing data obtained by receiving signals from a plurality of navigation satellites at a plurality of ground monitoring stations. Transmit to the navigation control station via the network, receive the signal transmitted after processing the error caused by the navigation satellite by the navigation control station by the geostationary satellite, and transmit the correction value to the user as a signal of a predetermined frequency, The protection level is calculated by the receiver processing unit from the position information obtained by the user receiving the signal from the geostationary satellite and the parameters calculated by the user, and when the protection level exceeds a predetermined alarm limit. In a satellite navigation receiving system that detects abnormalities and sends out alarms, in the range over the bubble that covers the horizontal and vertical alarm limits to detect obstacles And transmitting a radio wave through the antenna from,
Obstacle detecting means for receiving the radio wave reflected from the obstacle via the antenna at the receiver, control means for controlling the gain of the transmitter corresponding to the alarm limit for each flight phase of the user, and obstacle detecting means When an obstacle is detected, a signal processing unit that outputs an obstacle detection signal, and when an obstacle detection signal is input from the signal processing unit, or when a protection level from the receiver processing unit exceeds an alarm limit. And an alarm determining means for generating an alarm.

Further, in order to achieve the above object, the monitoring device of the present invention provides navigation control via a network which receives signals from a plurality of navigation satellites at a plurality of terrestrial monitoring stations. Transmitted to a station, processed by a navigation control station to handle errors caused by navigation satellites, received by a geostationary satellite, and transmitted by a geostationary satellite to transmit correction values from the geostationary satellite to the user. A monitoring device, a receiver processing unit for calculating a protection level from position information obtained by receiving a correction value from a geostationary satellite and a parameter calculated by itself, a flight course of a user and an alarm associated therewith A database that stores the limits in advance, a transmitter that transmits radio waves via the antenna in the range on the bubble that covers the horizontal and vertical alarm limits, and a database A control monitoring unit that extracts the alarm limit from the read data and controls the gain of the transmitter according to the alarm limit for each flight phase of the user, and transmits the radio wave transmitted via the antenna and reflected by obstacles to the antenna. A signal processing unit that outputs an obstacle detection signal when an obstacle is detected based on a reception signal of the receiver and an alarm limit for each flight phase, An alarm determination unit is provided that generates an alarm when an obstacle detection signal is input or when the protection level from the receiver processing unit exceeds an alarm limit.

In the satellite navigation receiving system and the monitoring apparatus according to the present invention, in addition to the function of calculating the horizontal and vertical protection levels in the receiver processing unit based on the parameters transmitted from the conventional terrestrial system, the function is independent of this. It is characterized in that a circuit unit for verifying this is provided. This circuit has a function of searching for an obstacle while changing a transmitter gain according to a flight phase of a user (for example, an aircraft).

That is, radio waves are transmitted in a range on a bubble which covers the horizontal and vertical alarm limits, and an obstacle near the actual flight path can be detected by detecting the disturbance of the reflected wave. . This result is integrated with the integrity monitoring results based on the conventional protection level, and performs the verification of the conventional function in a direct manner. Therefore, even if the calculated protection level is much lower than the original level due to some abnormality in the whole satellite navigation receiving system including the ground system, the user will autonomously You can check for obstacles.

[0023]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a block diagram of an embodiment of a monitoring device which is a main part of a satellite navigation receiving system according to the present invention. In the figure, the receiver processing unit 14 has the same configuration as the receiver processing unit 70 shown in FIG.
RE information 11, other error factors 12, and GIVE information 13 are received as inputs and the horizontal / vertical protection level 15 is output as in the prior art. However, unlike the prior art, in addition to this, It has a function of independently verifying the conventional monitoring function by autonomously detecting an obstacle on the user's aircraft side.

That is, in FIG.
6, control monitoring unit 17, transmitter 18, circulator 1
9, the antenna 110, the receiver 111, the signal processing unit 112, and the alarm determination unit 114 constitute a detection unit that autonomously detects an obstacle. The monitoring device having the configuration shown in FIG. 1 is mounted on an aircraft as a user.

The data of each flight path of the aircraft as the user is stored in the database 16 in advance, and an allowable deviation from a desired flight course of the aircraft is determined along with the data, and the deviation is also stored. Have been. This deviation is a value that becomes smaller as the aircraft moves from the enroute to the terminal area and finally to the landing. Further, the database 16 also stores horizontal and vertical alarm limits corresponding to each flight path of the aircraft.

The control monitor 17 extracts the deviation from the data read from the database 16 as an alarm limit, and determines the gain of the transmitter 18. Further, the control monitoring unit 17 extracts horizontal and vertical alarm limits from the database 16 and outputs them to the alarm determination unit 114.

The gain of the transmitter 18 is controlled by the control monitor 17 in proportion to the alarm limit. That is,
The gain of the transmitter 18 is controlled to provide the minimum power required for obstacle detection that may be within the alarm limits.

The output of the transmitter 18 is radiated from the antenna 110 via the circulator 19. The antenna 110 is basically assumed to be an omnidirectional antenna having a coverage area on a bubble in both the horizontal and vertical directions. When there is an obstacle 116, the radio wave radiated from the antenna 110 is reflected by the obstacle 116, received by the same antenna 110 as a reflected wave, and input to the receiver 111 via the circulator 19.

The reception signal input to the receiver 111 is subjected to predetermined reception processing, and then input to the signal processing unit 112 for analysis. When an obstacle is detected within the alarm limit, the signal processing unit 112 sends an obstacle detection signal 113 to the alarm determination unit 114 via the control monitoring unit 17. That is, the signal processing unit 112 can detect an obstacle near the actual flight path by detecting the disturbance of the reflected wave.

The alarm judging section 114 compares the result of comparison between the conventional horizontal / vertical protection level 15 with the horizontal / vertical alarm limit (the result of integrity monitoring based on the conventional protection level) and the obstacle detection signal 113 described above. Merge (eg, OR) and integrity alarm 1
15 is output.

That is, the alarm determination unit 114 determines whether or not a comparison result in which at least one of the conventional horizontal protection level and vertical protection level 15 exceeds the horizontal alarm limit or the vertical alarm limit is obtained. When an obstacle detection signal 113 indicating that the accuracy has exceeded the alarm limit is also input, an integrity alarm 115 is output. The integrity alarm 115 drives some notification means in the cockpit of the aircraft to notify the pilot of the alarm.

Next, the operation of this embodiment will be described in more detail with reference to FIGS. FIG. 2 shows an example of the relationship between the change in vertical accuracy, the protection level, and the alarm limit when the aircraft is flying, taking vertical accuracy as an example. As described above, no one can know the true position of the aircraft, which is the user, and the aircraft side actually detects the presence or absence of an abnormality based on the relationship between the protection level and the alarm limit. Is shown by a solid line 21 from the flight course. The horizontal axis is time,
These changes on the time axis are shown. However, the alarm limit was set to a constant value as shown by a dotted line 23 in this time range.

A broken line 22 in FIG. 2 indicates a change in the vertical protection level. In the vicinity of the center of FIG. 2, the vertical accuracy 21 changes more greatly than others. This indicates that the error has increased for some reason. At this time, the vertical protection level 22 is also increased according to this change. This indicates that a bad condition has been correctly detected and is reflected in the vertical protection level 22. In other words, the system operates properly in detecting an abnormality.

The vertical protection level 22 of FIG. 2 is input from the receiver processing unit 14 of FIG. 1 to the alarm judgment unit 114, where it is compared with the vertical alarm limit from the control monitoring unit 17, and is indicated by 24 in FIG. As described above, when the vertical protection level 22 exceeds the alarm limit 23, the alarm determination unit 11
4 outputs an integrity alarm 115 normally.

On the other hand, FIG. 3 shows another example of the relationship between the change in vertical accuracy, the vertical protection level, and the alarm limit when the aircraft is flying, taking vertical accuracy as an example as in FIG. 3 shows a case where the conventional integrity function does not work properly. In FIG. 3, the range indicated by 34 is different from that of FIG.
The relationship is reversed. This indicates that the actual error is not protected by the vertical protection level 32.

As described above, since the aircraft operates with confidence in the vertical protection level 32, if the vertical protection level 32 becomes smaller than the vertical precision 31, the aircraft will not be output because no alarm is output, and the aircraft will be in danger. become. The range 35 is in this state, the vertical accuracy 31 is the alarm limit 33
Indicates a section that also exceeds. Even if the vertical accuracy 31 exceeds the alarm limit 33, an accident does not occur immediately, but if an obstacle exists, it can be said that there is a potential possibility of causing a major accident. Therefore, a function for independently verifying such a passive integrity monitoring function is essential.

Therefore, in this embodiment, the detection unit including the database 16, the control monitoring unit 17, the transmitter 18, the circulator 19, the antenna 110, the receiver 111, the signal processing unit 112, and the alarm determination unit 114 shown in FIG. And independently verifies the passive integrity monitoring function. The operation of this independent verification function will be described with reference to FIGS.

In FIG. 4, the aircraft 41 shows the movement of the final approach from the enroute. Here, the aircraft 41
Is actually 4 for the planned flight course 42
Make the flight indicated by 3. The transmission output of the transmitter 18 and the receiver 1 of FIG. 1 controlled to a gain corresponding to the alarm limit 47 according to each flight phase (enroute, precision approach, etc.)
The antenna coverage area on the bubble by the reception input of No. 11 is indicated by 44a to 44e in FIG. In FIG. 4, it can be seen that this radiation pattern corresponds to the alarm limit 47, and the operation of the aircraft 41 is normally performed.

In FIG. 4, a mountain 45 is shown as a representative of the obstacle on the enroute, and a building 46 is shown as an obstacle in the terminal area. These mountains 45 and buildings 46 are located below the alarm limit 47, and the safety of the aircraft 41 operating with confidence in the protection level is secured.

On the other hand, FIG. 5 shows a case where the situation described above with reference to FIG. 3 occurs and the actual error greatly exceeds this level, although the vertical protection level is seemingly normal. Is shown. 4, the same parts as those of FIG. 4 are denoted by the same reference numerals, and the description thereof will be omitted. In FIG. 5, the alarm limit based on the desired flight course 42 is 47
Are the same as those in FIG. 4, but the actual aircraft 4
One flight course will be as shown at 50. Therefore, if the alarm limit is temporarily plotted with reference to the actual aircraft position, it will be as shown by a two-dot chain line 48 in FIG. 5, and the mountain 45 which is an obstacle is in conflict.

In the bubble cover area 44b, the peak of the peak 45 is 4
At this time, the vertical accuracy exceeds the vertical alarm limit as shown in the range 35 shown in FIG. However, in this embodiment, the radio wave radiated from the transmitter 18 via the circulator 19 and the antenna 110 at this time is reflected by the mountain 45 and reflected by the receiver 111 via the antenna 110 and the circulator 19 as a reflected wave. Received.

The received signal is processed by a signal processing unit 112 with respect to a received signal input of a predetermined level or more, and an obstacle detection signal 113 is output from the control monitoring unit 17 of FIG. To enter. As a result, an integrity alarm 115 is output from the alarm determination unit 114, and it can be notified that an obstacle is approaching the pilot. Therefore, in this embodiment, the reliability of the integrity monitoring function can be remarkably improved as compared with the related art.

In the above embodiment, the omnidirectional antenna 110 is assumed in order to make the configuration as simple and inexpensive as possible. However, the present invention is not limited to this.
For example, the basic configuration is the same as in the above embodiment, but it is also possible to detect an obstacle using an electronically operated antenna instead of the antenna 110. In addition, GP
Since satellites equivalent to the S satellites 601 to 604 are being developed, these other equivalent satellites can be applied to the present invention instead of the GPS satellites 601 to 604.

[0044]

As described above, according to the present invention,
If the calculated protection level is much lower than the original level due to some abnormality in the whole satellite navigation receiving system including the ground system (the user cannot detect the abnormality and the protection level falls below the actual error). Even if this happens, the user can autonomously check for obstacles, so that alarms can be detected actively, and the reliability of the integrity monitoring function of the satellite navigation receiver system can be improved. And safety can be significantly improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of a main part of the present invention.

FIG. 2 is a diagram illustrating an example of a relationship among vertical accuracy, a vertical protection level, and an alarm limit.

FIG. 3 is a diagram illustrating another example of the relationship between the vertical accuracy, the vertical protection level, and the alarm limit.

FIG. 4 is a conceptual diagram of the integrity monitoring operation of the present invention (in a normal state).

FIG. 5 is a conceptual diagram of an integrity monitoring operation according to the present invention (when an abnormality occurs).

FIG. 6 is an overall view of an example of an SBAS system.

FIG. 7 is a block diagram illustrating an example of a conventional integrity monitor.

[Explanation of symbols]

 14 Receiver processing unit 15 Horizontal / vertical protection level 16 Database 17 Control monitoring unit 18 Transmitter 19 Circulator 21, 31 Vertical accuracy 22, 32 Vertical protection level 23, 33 Alarm limit 24, 35 Error detection range 24 Integrity error occurrence range 41 , 606 Aircraft 42 Desired flight course 43, 50 Actual flight course 44a-44e Bubble skyline coverage 47 Alarm limit based on desired flight course 61-64 Ground monitoring station 65a-65h GPS signal 66 Navigation control station 67 GNSS network 69 SBAS signal 110 Antenna 111 Receiver 112 Signal processing unit 113 Obstacle detection signal 114 Alarm determination unit 115 Integrity alarm

Claims (5)

[Claims] 1. A method in which signals from a plurality of navigation satellites are received by a plurality of monitoring stations on the ground, and processing data obtained is transmitted to a navigation control station via a network. A signal transmitted after processing the error to be received by the geostationary satellite, the correction value is transmitted to the user as a signal of a predetermined frequency, and the position information obtained by the user receiving the signal from the geostationary satellite, In a satellite navigation receiving system in which a protection level is calculated by a receiver processing unit from parameters calculated by the user himself, and when the protection level exceeds a predetermined alarm limit, an abnormality is detected and an alarm is transmitted. In order to detect an object, a radio wave is transmitted from the transmitter via the antenna in a range on the bubble which covers the horizontal and vertical alarm limits, and the electric power reflected from the obstacle is reflected. Obstacle detecting means for receiving at the receiver via the antenna, control means for controlling the gain of the transmitter corresponding to the alarm limit for each flight phase of the user, obstacles by the obstacle detecting means When is detected,
A signal processing unit that outputs an obstacle detection signal; and an alarm is generated when the obstacle detection signal is input from the signal processing unit or when a protection level from the receiver processing unit exceeds the alarm limit. A satellite navigation receiving system, comprising: 2. The satellite navigation receiving system according to claim 1, wherein said user is an aircraft, and said navigation satellite is an orbiting satellite. 3. The satellite navigation receiving system according to claim 1, wherein said user is an aircraft, and said antenna is an omnidirectional antenna. 4. Processing data obtained by receiving signals from a plurality of navigation satellites at a plurality of terrestrial monitoring stations and transmitting the processed data to a navigation control station via a network. A signal transmitted from the geostationary satellite after processing the error to be processed, and a monitoring device mounted on the user of the satellite navigation system for transmitting a correction value from the geostationary satellite to the user; Position information obtained by receiving the correction value,
A receiver processing unit for calculating a protection level from the parameters calculated by itself, a database preliminarily storing the flight course of the user and alarm limits associated therewith, and covering the horizontal and vertical alarm limits A transmitter that transmits radio waves through an antenna in a range on a bubble, and extracts the alarm limit from data read from the database and adjusts the gain of the transmitter corresponding to the alarm limit for each flight phase of the user. A control monitoring unit that controls, a receiver that receives, via the antenna, a radio wave transmitted through the antenna and reflected by an obstacle, based on a reception signal of the receiver and an alarm limit for each of the flight phases. A signal processing unit that outputs an obstacle detection signal when an obstacle is detected; When object detection signal is input, or monitoring apparatus characterized by having an alarm decision unit for generating an alarm when the level of protection from the receiver unit exceeds the alarm limit. 5. The monitoring device according to claim 4, wherein the user is an aircraft, and the aerial is an omnidirectional antenna.