JP3407705B2 - Satellite navigation reception system and monitoring device - Google Patents

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 satellite navigation system (GNSS) using artificial satellites.
satellite navigation receiving system and monitoring device called "telite system".

[0002]

2. Description of the Related Art Conventional global satellite navigation systems (GN)
For SS, satellite-based wide area reinforcement system (SB)
AS: Satellite Based Augmentation System) will be described as an example. In addition, the Global Positioning System (GPS) which is a navigation satellite referred to in this specification.
System) artificial satellites (hereinafter referred to as GPS satellites) have been published and publicly known as "Basics of GPS surveying" by the Japanese Surveying Society and many others, and the description thereof will be omitted. Hereinafter, as a description of the conventional technique, (1) outline of SBAS, (2) processing of integrity information in the receiving system, and (3) other conventional techniques related to integrity will be performed in this order.

(1) Outline of SBAS FIG. 6 shows an overall system diagram of an example of SBAS. In the figure, the monitoring stations 61 to 64 on the ground are GPS satellites 601.
The signals 66a to 66h from ˜604 are received, and the processed data are transmitted to the navigation control station 66 via the GNSS network 67. The navigation control station 66 has monitoring stations 61 to 61.
The information from 64 is processed and the uplink signal 68 is transmitted to the geostationary satellite 605. The geostationary satellite 605 converts the carrier signal to a predetermined frequency, emits the SBAS signal 69 over a wide area, and transmits the downlink signal 68 to the navigation control station 66. This SBAS signal 69 is mainly 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. Providing a GPS-like signal The navigation control station 66 sends a signal to a predetermined pseudo random code (Psuedo Ran) in the same manner as the GPS C / A code.
dom Noise Code: Modulated by PRN code. When this is sent out via 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 arrangement change affects positioning errors.
Delivering the AS signal 69 will always result in a source that provides a stable signal from the same location, improving system reliability.

B. Providing differential correction information GPS has various error factors. Among them, the error caused by the satellite becomes a common error factor in the receivers which receive the signal from the same satellite. The error caused by the satellite includes, for example, an error that changes relatively quickly such as a clock error of the satellite and an error that changes relatively slowly like the position (ephemeris) of the satellite. This error is S
It is extracted as a correction term from the GPS data received by the BAS ground monitoring stations 61 to 64, and this is superposed as a separate message (Fast Correction and Long Term Correction) on the previous GPS-like signal. The user (aircraft 605) side can use this to correct the pseudorange obtained by performing positioning with its own receiver, and thereby allow the user to perform highly accurate positioning.

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

UDRE is a GPS satellite 601-60
4 is calculated individually, and when it exceeds a predetermined value, it also serves as a flag that prohibits the use of the GPS satellite. That is, the abnormality of the corrected error is constantly monitored, and when there is an abnormality, 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 abnormality 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 ground navigation control station 66 can perform processing related to the error caused by the GPS satellites 601 to 604, but does not cause the error caused by the GPS satellites 601 to 604. Factor,
For example, the clock error and the troposphere error of the user receiver are calculated by the user receiver based on a predetermined algorithm. A parameter called a protection level is obtained by integrating these residual errors and multiplying them by a predetermined coefficient (called a K value). 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
The value of 6.33 is used. This is 1-10-7 when the integrated error distribution is regarded as a Gaussian distribution.
The region included with the probability of is shown. In other words, the user (aircraft 605) uses the information received from the navigation control station 66 and the information obtained by self-confidence to calculate 1-10-
It is possible to calculate the level of protection with a probability of 7. Even if some malfunction related to the positioning of the user (aircraft 605) occurs, the protection level increases as the residual error increases. If this exceeds the preset alarm limit, the user (aircraft 6
In 05), an abnormality can be detected and an accident can be prevented.

FIG. 7 shows a block diagram of an example of the integrity monitoring. The algorithm of the user receiver is document 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 the navigation control station on the ground via a geostationary satellite. In addition to this, the navigation control station also transmits the ionospheric vertical delay error for each grid point (grid point) when the ground is cut with a mesh of a predetermined width. This is usually called GIVE (Grid Ionospheric Vertical Error), and is shown 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 the geostationary satellite.

Parameter 1 transmitted from these grounds
The receiver processing unit 70 for calculating the above-described protection level from the parameters 1 to 13 and the on-board parameter is the calculation processing unit 71.
And 72, an integrated processing unit 75 for the variance 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 the short-term correction and the long-term correction are applied. The calculation processing unit 72 uses the GI
The calculation processing unit estimates the ionospheric error at the user position based on the VE information 13. On the other hand, the variance of all satellites σ
The integration processing unit 75 of 2 integrates errors such as the variance value 73 of the receiver error and the variance value 74 of the troposphere error, and multiplies the K value in the protection level calculation processing unit 76,
The horizontal protection level and 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 by taking an example of the relationship between the vertical accuracy and the vertical protection level alarm limit. Vertical accuracy 21 shown in FIG.
Is illustrated assuming that the true value is known because the user cannot know the true position. Therefore, how much the user can trust the result of positioning by applying the correction value depends on the reliability of the protection level calculated as described above. In addition, in FIG. 2, a broken line 22 indicates a change in the protection level with the passage of time. If the value of this protection level is within the alarm limit 23, the user
The probability of 1-10-7 is considered to be within the allowable range. Further, the arrow 24 indicates a state in which the protection level exceeds the alarm limit 23.

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

[0015]

However, the above-mentioned conventional satellite navigation receiving system has a problem that the integrity monitoring is passive. That is, conventionally, the integrity monitoring is performed on the assumption that this depends on the parameters derived from the ground station. Therefore, if some kind of abnormality occurs, and the UDRE value is actually a very large value, but the ground level sends a small UDRE value, and the protection level is calculated to be smaller than the actual value, User's aircraft 6
05 is a risk factor.

Further, due to some abnormal occurrence, 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,
A solid line 31 indicates vertical accuracy, a broken line 32 indicates a vertical protection level, and a dotted line 33 indicates an alarm limit. Where vertical accuracy 31
In the portion indicated by 34, the relationship between the vertical protection level and the precision is reversed. In this case, the user, the aircraft 60
No. 5 does not know the actual error, judges that there is no problem by looking at the vertical protection level 32, and does not detect an alarm.
This suggests that the system may not be able to detect the anomaly even if the aircraft 605 is approaching an obstacle.

The present invention has been made in view of the above points,
An object of the present invention is to provide a satellite navigation receiving system and a monitoring device capable of actively detecting an alarm even when the user side cannot detect an abnormality and the protection level becomes equal to or less than the 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 the position information provided passively on the user side. To provide a monitoring device.

[0019]

In order to achieve the above object, the satellite navigation receiving system of the present invention provides processed data obtained by receiving signals from a plurality of navigation satellites at a plurality of ground monitoring stations. It is transmitted to the navigation control station via the network, the navigation control station processes the error caused by the navigation satellite, and then the signal transmitted by the geostationary satellite is received and the correction value is transmitted to the user as a signal of a predetermined frequency, The receiver processing unit calculates the protection level from the position information obtained by the user receiving the signal from the geostationary satellite and the parameter calculated by the user, and when the protection level exceeds a predetermined alarm limit. In a satellite navigation receiving system that detects anomalies and sends out an alarm, in order to detect obstacles, it transmits in the range above the bubble that covers the horizontal and vertical alarm limits. And transmitting a radio wave through the antenna from,
By the obstacle detection means that receives the radio waves reflected from the obstacle via the antenna at the receiver, the control means that controls the gain of the transmitter corresponding to the alarm limit of each flight phase of the user, and the obstacle detection 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 the protection level from the receiver processing unit exceeds the alarm limit. It is characterized by having an alarm judging means for occasionally generating an alarm.

Further, in order to achieve the above-mentioned object, the monitoring device of the present invention controls the navigation data via the network by processing data obtained by receiving signals from a plurality of navigation satellites at a plurality of terrestrial monitoring stations. It is installed in the user of the satellite navigation system that transmits the correction value to the user by receiving the signal transmitted by the geostationary satellite after receiving the signal transmitted by the navigation control station after processing the error caused by the navigation satellite by the navigation control station. The monitoring device is a receiver processing unit that calculates 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 the user, and an alarm associated with the flight course. A database that stores limits in advance, a transmitter that transmits radio waves through the antenna in the range above the bubble that covers the horizontal and vertical alarm limits, and a database. An alarm limit is extracted from the read data to control the gain of the transmitter according to the alarm limit of each flight phase of the user, and a radio wave transmitted via the antenna and reflected by an obstacle is transmitted to the antenna. A signal processing unit that outputs an obstacle detection signal when an obstacle is detected based on the receiver received via the receiver, the reception signal of the receiver, and the alarm limit for each flight phase; The configuration includes an alarm determination unit that issues an alarm when an obstacle detection signal is input or when the protection level from the receiver processing unit exceeds the alarm limit.

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

That is, by transmitting radio waves in a range on a bubble whose horizontal and vertical alarm limits are covered and detecting the disturbance of the reflected waves, obstacles in the vicinity of the actual flight path can be detected. . This result is integrated with the integrity protection result based on the conventional protection level to perform the verification by the direct method of the conventional function. Therefore, even if there is a possibility that the calculated protection level or the original level will drop significantly due to some abnormality in the entire satellite navigation receiving system including the ground system, the user can autonomously operate. You can check the existence of obstacles.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION 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.
The RE information 11, the other error factors 12, and the GIVE information 13 are received as inputs and the horizontal / vertical protection level 15 is output, which is the same as the conventional one, but unlike the conventional one, in addition to this, this embodiment is It has a function of independently verifying the conventional monitoring function by autonomously detecting an obstacle on the side of the aircraft which is the user.

That is, in FIG. 1, the database 1
6, control monitoring unit 17, transmitter 18, circulator 1
The antenna 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 configured as shown in FIG. 1 is installed in an aircraft, which is a user.

The data of each flight route of the aircraft which is the user is stored in advance in the database 16, and the allowable deviation from the desired flight course of the aircraft is determined in association therewith, and the deviation is also stored. Has been done. This deviation is a value that decreases as the aircraft approaches the final route from the enroute to the terminal area. Further, the database 16 also stores horizontal and vertical alarm limits corresponding to each flight path of the aircraft.

The control monitoring section 17 extracts the deviation as an alarm limit from the data read from the database 16 and determines the gain of the transmitter 18. The control monitoring unit 17 also 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 transmitter 18 is controlled to provide the minimum power required to detect obstacles that may be within the alarm limits.

The output of the transmitter 18 is emitted from the antenna 110 via the circulator 19. The antenna 110 is basically an omnidirectional antenna in both horizontal and vertical directions, and is assumed to have a bubble coverage area. When there is an obstacle 116, the radio wave radiated from the antenna 110 is reflected by the obstacle 116, is received by the same antenna 110 as a reflected wave, and is 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 determination unit 114 compares the result of comparison between the conventional horizontal / vertical protection level 15 and the horizontal / vertical alarm limit (integrity monitoring result based on the conventional protection level) and the obstacle detection signal 113. Integrated (eg ORed) and integrity alarm 1
15 is output.

That is, the alarm determination unit 114 is not limited to the case where a comparison result is obtained in which at least one of the horizontal protection level 15 and the vertical protection level 15 of the related art exceeds the horizontal alarm limit or the vertical alarm limit. The integrity alarm 115 is also output when the obstacle detection signal 113 indicating that the accuracy exceeds the alarm limit is input. 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 that is the user, and the aircraft side actually detects the presence or absence of an abnormality in the relationship between the protection level and the alarm limit. The vertical accuracy from the flight course is shown by the solid line 21. The horizontal axis is time,
The changes on these time axes are shown. However, the alarm limit is set to a constant value as shown by the dotted line 23 in this time range.

The broken line 22 in FIG. 2 shows the change in the vertical protection level. The vertical accuracy 21 changes more greatly than the other in the vicinity of the center of FIG. This indicates that the error increased due to some factor. At this time, the vertical protection level 22 also increases according to this change. This means that the bad condition is correctly detected and reflected in the vertical protection level 22. In other words, the system is operating correctly in terms of 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 determination unit 114, where it is compared with the vertical alarm limit from the control and monitoring unit 17, and is shown at 24 in FIG. Thus, when the vertical protection level 22 exceeds the alarm limit 23, the alarm determination unit 11
4 outputs the integrity alarm 115 normally.

On the other hand, similarly to FIG. 2, 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. 3 shows the case where the conventional integrity function does not work properly. 3, the range indicated by 34 is different from the case of FIG. 2 in that the vertical precision 31 and the vertical protection level 32 are
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 by trusting the vertical protection level 32, if the vertical protection level 32 becomes smaller than the vertical accuracy 31, the aircraft will be at risk because no alarm is output. become. In this range, the vertical precision 31 is the alarm limit 33 in the range 35.
Indicates a section that also exceeds. Although the vertical accuracy 31 exceeds the alarm limit 33, an accident does not occur immediately, but it can be said that if an obstacle is present, it may lead to a serious accident. Therefore, a function of 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. In this case, the passive integrity monitoring function is independently verified, and the operation of this independent verification function will be described with reference to FIGS. 4 and 5.

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
Take the flight indicated by 3. The transmission output of the transmitter 18 of FIG. 1 and the receiver 1 controlled to gain corresponding to the alarm limit 47 corresponding to each flight phase (enroute, precision approach, etc.)
The antenna coverage areas on the bubble due to the reception input of 11 are 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 that the aircraft 41 is operating normally.

In FIG. 4, a mountain 45 is shown as a representative of obstacles on the enroute, and a building 46 is shown as an obstacle in the terminal area. The mountain 45 and the building 46 are located below the alarm limit 47, and the safety of the aircraft 41 operating while trusting the protection level is ensured.

On the other hand, in FIG. 5, when the situation as described in FIG. 3 occurs, the actual error largely exceeds this even though the vertical protection level is seemingly normal. Is shown. In the figure, those parts which are the same as those corresponding parts in FIG. 4 are designated by the same reference numerals, and a description thereof will be omitted. In FIG. 5, the alarm limit based on the desired flight course 42 is 47.
4 is the same as in FIG. 4, but the actual aircraft 4
The flight course of 1 is shown by 50. Therefore, if the alarm limit is plotted based on this actual aircraft position, it becomes as shown by the chain double-dashed line 48 in FIG. 5, and it is in contact with the mountain 45 which is an obstacle.

There are four peaks of the mountain 45 in the bubble coverage area 44b.
As indicated by reference numeral 9, the vertical precision exceeds the vertical alarm limit at this time as in the range 35 shown in FIG. However, in this embodiment, at this time, the radio wave radiated from the transmitter 18 through the circulator 19 and the antenna 110 is reflected by the mountain 45 and reflected as a reflected wave at the receiver 111 through the antenna 110 and the circulator 19. Be received.

The received signal is processed by the signal processing unit 112 with respect to the received signal input of a predetermined level or higher, and the obstacle detection signal 113 is output from the control and monitoring unit 17 of FIG. To enter. Thereby, the integrity alarm 115 is output from the alarm determination unit 114, and it is possible to notify the pilot that the obstacle is approaching. Therefore, in this embodiment, the reliability of the integrity monitoring function can be significantly improved as compared with the conventional one.

In the above embodiment, the omnidirectional antenna 110 is assumed in order to make the structure as simple and inexpensive as possible, but the present invention is not limited to this.
For example, although the basic configuration is the same as that of the above-described embodiment, it is possible to detect an obstacle by using an electronically operated antenna instead of the antenna 110. Also, currently in each country
Since satellites equivalent to the S satellites 601 to 604 are being developed, 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,
When the calculated protection level or the actual level is significantly lower than the calculated level due to some abnormality in the entire satellite navigation receiving system including the ground system (the user cannot detect the abnormality and the protection level falls below the actual error). If an error occurs), the user can autonomously check the presence or absence of an obstacle, so that an alarm can be actively detected. Therefore, the reliability of the integrity monitoring function of the satellite navigation receiving system can be improved. It can be improved and safety can be remarkably improved.

[Brief description of drawings]

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

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

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

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

FIG. 5 is a conceptual diagram (at the time of abnormality) of an integrity monitoring operation of the present invention.

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

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

[Explanation of symbols]

14 Receiver processing unit 15 Horizontal / vertical protection level 16 database 17 Control and monitoring section 18 transmitter 19 Circulator 21, 31 Vertical accuracy 22, 32 Vertical protection level 23, 33 Alarm limit 24, 35 Abnormality detection range 24 Integrity abnormality occurrence range 41,606 aircraft 42 desired flight course 43,50 Actual flight course 44a to 44e Bubble aerial coverage area 47 Alarm limit based on desired flight course 61-64 Ground monitoring station 65a-65h GPS signal 66 Navigation Control Bureau 67 GNSS network 69 SBAS signal 110 Aerial 111 receiver 112 signal processor 113 Obstacle detection signal 114 Alarm determination section 115 Integrity alarm

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Claims (5)

(57) [Claims] 1. Processing data obtained by receiving signals from a plurality of navigation satellites at a plurality of terrestrial monitoring stations is transmitted to a navigation control station via a network, and the navigation control station causes the navigation satellites to generate the processed data. Position information obtained by receiving the signal transmitted from the geostationary satellite by receiving the signal transmitted from the geostationary satellite by receiving the signal from the geostationary satellite by receiving the correction value as a signal of a predetermined frequency by processing the error transmitted by the geostationary satellite, In the satellite navigation receiving system, the receiver processing unit calculates the protection level from the parameters calculated by the user and detects an abnormality when the protection level exceeds a predetermined alarm limit and sends an alarm. To detect an object, the transmitter transmits radio waves through the antenna in the range above the bubble that covers the horizontal and vertical alarm limits, and the electric waves reflected from the obstacle are detected. To the receiver via the antenna, a control unit for controlling the gain of the transmitter in response to the alarm limit of each flight phase of the user, and an obstacle by the obstacle detection unit. 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 the 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 the user is an aircraft and the navigation satellite is an orbiting satellite. 3. The satellite navigation receiving system according to claim 1, wherein the user is an aircraft and the antenna is an omnidirectional antenna. 4. The processing data obtained by receiving signals from a plurality of navigation satellites at a plurality of ground monitoring stations are transmitted to a navigation control station via a network, and the navigation control station causes the navigation satellites to cause the data. A monitoring device mounted on the user of a satellite navigation system that receives a signal transmitted by a geostationary satellite after processing the error, and transmits a correction value to the user from the geostationary satellite. Position information obtained by receiving the correction value,
A receiver processing unit that calculates the protection level from the parameters calculated by itself, a database that stores in advance the flight course of the user and the alarm limits associated therewith, and the horizontal and vertical alarm limits as the coverage area. A transmitter that transmits radio waves in the range on the bubble through the antenna, and the alarm limit is extracted from the data read from the database, and the gain of the transmitter is set corresponding to the alarm limit for each flight phase of the user. Based on a control monitoring unit that controls, a receiver that receives radio waves transmitted through the antenna and reflected by an obstacle through the antenna, and a reception signal of the receiver and an alarm limit for each flight phase. A signal processing unit that outputs an obstacle detection signal when an obstacle is detected, and the obstacle from the signal processing unit. 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 antenna is an omnidirectional antenna.