JP3492866B2 - System performance calculation apparatus and system performance calculation method - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a GPS (Global P
The present invention relates to a system performance calculation device and system performance calculation method for calculating system performance in a positioning system using artificial satellites such as satellites.

[0002]

2. Description of the Related Art In recent years, GNSS (Gl
The obal Navigation Satellite System) has been widely used for positioning various moving objects such as aircraft, ships, and automobiles. Further, a system for applying air traffic control by applying GNSS is also considered.

In the case of a system requiring good effectiveness such as air traffic control, it is necessary to construct an appropriate system while considering the system performance of GNSS. Therefore, in the system design stage, it is necessary to repeatedly calculate the system performance of the GNSS according to the design parameters.

The system performance of GNSS is as follows.
There is availability and continuity. In order to calculate the system performance of such a GNSS, conventionally, the flight of a GPS satellite is simulated by a satellite orbit simulator to observe the transition situation of positioning accuracy at an arbitrary position, and the system is determined from this transition status of positioning accuracy. Performance is being calculated.

The effectiveness of GNSS and the like are shown in the following documents.

Research institution name (stanford Telecom) Woody S. Phlong et al, “Availability Characterisrt
ic of GPS and Augmentation Alternatives ”, Journal
of the Institute of Navigation No.4, V0l.14, Winte
r 1993-1994. Research Organization Name (wilcox) Mitch Sams, “Satellite Navigation Accuracy and Av
ailability Modelingas an Air Traffic Management To
ol ”, the Institute of Navigation National Techni
cal Meeting, Jan., 1995. By the way, in order to accurately grasp the system performance of GNSS, it is necessary to consider the failure of GPS satellites. Therefore, it is necessary to repeatedly calculate the system performance described above while changing the setting of the failure status of the GPS satellite in various ways. That is, the satellite orbit simulator was started for each of various failure situations to generate observation data. The satellite orbit simulator performs orbit calculation every moment, and has a considerable amount of calculation, and the amount of calculation in the whole system performance calculation is enormous.

Further, in the case of an air traffic control system to which GNSS is applied, in order to obtain higher effectiveness, a geostationary satellite (GEO: Geo-Earth Orbital satell) is added in addition to a GPS satellite.
It is also considered to use it, but in such a system, the amount of calculation for calculating the system performance becomes even more enormous.

[0008]

As described above, the prior art is as follows.
Since the system performance is calculated while repeatedly simulating the flight of GPS satellites, the amount of calculation is enormous and it takes a lot of time.

The present invention has been made in consideration of such circumstances, and an object of the present invention is to provide a system performance calculation device capable of performing system performance calculation in a short time with a small calculation amount. It is to provide a system performance calculation method.

[0010]

In order to achieve the above object, the system performance calculation method of the present invention determines the flight conditions of a large number of artificial satellites such as GPS satellites and geostationary satellites within a predetermined simulation period. Simulate, at every predetermined observation time point at a predetermined time interval, while detecting all artificial satellites that transmit receivable signals with radio performance capable of positioning at a predetermined observation point as visible satellites, A simulation step of calculating the direction of each of the detected visible satellites based on the observation point, and based on the result of the simulation in this simulation step, while detecting all combinations of a predetermined number of visible satellites for each observation time point,
Positioning accuracy (for example, DOP) by a predetermined number of visible satellites included in each detected combination is calculated, and a data set in which the observation time point, the combination of the predetermined number of visible satellites, and the positioning accuracy are associated with one observation point. A data table creating step of creating a data table summarizing each of the observation points, and a failure of the artificial satellite from all the data sets included in the data table when the failure of the artificial satellite is not assumed. In the case of assuming, from among the remaining data sets excluding the data set including the failed satellite among the data sets included in the data table,
A positioning accuracy calculation step for obtaining the positioning accuracy under an arbitrary failure condition by detecting the best positioning accuracy at each observation point, and system performance related to the system based on the positioning accuracy calculated in this positioning accuracy calculation step. The system performance is calculated by the system performance calculation step of calculating (for example, effectiveness).

Further, the present invention provides a system performance calculation device for realizing the calculation of the system performance by the method for calculating the system performance, for each flight of a large number of artificial satellites such as GPS satellites and geostationary satellites within a predetermined simulation period. Simulate the situation and detect all visible satellites that transmit receivable signals with radio performance capable of positioning at predetermined observation points at predetermined observation points at predetermined time intervals. With
A combination of a simulation means such as a satellite orbit simulator for calculating the direction of each of the detected visible satellites based on the observation point and a predetermined number of visible satellites for each observation time point based on the result of the simulation by the simulation means. And the positioning accuracy (for example, DOP) by a predetermined number of visible satellites included in each detected combination is calculated, and the observation time point, the combination of the predetermined number of visible satellites, and the positioning accuracy are associated with each other. Data table creation and storage means, such as a positioning accuracy recording device, which creates and stores a data table in which data sets for one observation point are created and stored for each of the observation points, and the data when the failure of the artificial satellite is not assumed. From all the data sets included in the table, In the case of assuming, from among the remaining data sets excluding the data set including the failed satellite among the data sets included in the data table, by detecting the best positioning accuracy at each observation time point Positioning accuracy calculation means such as a positioning accuracy calculation device at the time of failure for obtaining positioning accuracy under a failure condition, and system performance (eg effectiveness) relating to the system is calculated based on the positioning accuracy calculated by this positioning accuracy calculation means. And a system performance calculation means such as an effectiveness calculation means.

By taking such a measure, by referring to the data table created by the data table creating and storing means on the basis of the result of one simulation by the simulating means, the positioning accuracy under various failure situations can be obtained. The system performance calculation in consideration of the above is performed without repeating the simulation by the simulation means.

[0013]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a functional block diagram showing the configuration of the system performance calculation apparatus according to this embodiment.

As shown in this figure, the system performance calculation apparatus according to the present embodiment comprises a control apparatus 1, a satellite orbit simulator 2, a positioning accuracy recording apparatus 3, and a failure positioning accuracy calculation apparatus 4.
And a validity calculation device 5. The satellite orbit simulator 2, the positioning accuracy recording device 3, the failure positioning accuracy calculation device 4, and the effectiveness calculation device 5 are connected to the control device 1, respectively. Further, the satellite orbit simulator 2 and the positioning accuracy recording device 3, the positioning accuracy recording device 3, the failure positioning accuracy calculation device 4, and the failure positioning accuracy calculation device 4 and the effectiveness calculation device 5 are respectively connected.

The control device 1 includes a satellite orbit simulator 2,
The operation as the system performance calculation device is realized by centrally controlling the operations of the positioning accuracy recording device 3, the failure positioning accuracy calculation device 4, and the effectiveness calculation device 5.

The satellite orbit simulator 2 is capable of calculating an observation satellite (hereinafter referred to as a visible satellite) that is visible from that position at an arbitrary time and the direction of each visible satellite with respect to an arbitrary space-time coordinate. Note that “visible” means that the signal transmitted by the observation satellite concerned can be received with the radio performance (eg, SN ratio) capable of positioning.

The positioning accuracy recording device 3 detects all combinations of any four visible satellites at one time point, obtains the positioning accuracy of the four observation satellites of each combination, and determines each of these positioning accuracy. A data table associated with the IDs of the observation satellites included in the combination is created, and the created data table is stored.

The faulty positioning accuracy calculation device 4 refers to the data table stored in the positioning accuracy recording device 3,
As a preprocessing of the effectiveness calculation, the time probability of positioning accuracy is calculated while considering the failure of the observation satellite.

The effectiveness calculation device 5 calculates the availability of the system which is the target of the system performance calculation, using the calculation result of the failure positioning accuracy calculation device 4.

Next, the operation of the system performance calculation device configured as described above will be described. In addition, here, GNSS (Global Navigation Satellite System) using GPS is used.
The case of calculating the effectiveness for m) is illustrated.

First, the control device 1 causes the satellite orbit simulator 2 to perform the simulation only once, and
The positioning accuracy recording device 3 is made to create a data table.

The satellite orbit simulator 2 simulates the flight of a GPS satellite and divides a predetermined simulation period into predetermined time intervals and sets visible satellites from arbitrary space-time coordinates at each of a large number of time points and the respective visible satellites. The direction is calculated, and the calculation result is given to the positioning accuracy recording device 3.

The time interval which is a space-time parameter of the satellite orbit simulator 2 is about 1 minute or 5 minutes. This is because it is considered that the GPS satellites do not move much in a short time and the visibility and the direction change little. In this way, it is usual to take the time intervals rather coarsely and perform the simulation. In addition, the simulation period is often one day in the time of the satellite coordinate system. This is adopted as an appropriate value for one round of the arrangement of all GPS satellites (24 in the ideal arrangement).

In the case of a simple case, the space coordinate that the satellite orbit simulator 2 simulates is one point. This is a case where a system that performs positioning in a narrow area such as an airport is targeted for performance calculation. In contrast, the airport information area FIR (Flight Information Region)
When a system that performs positioning in a wide area, such as), is targeted for performance calculation, the area is divided by a roughness of about 5 degrees longitude and latitude, and one spatial coordinate is set for simulation for each division. That is, the satellite orbit simulator 2
There are multiple spatial coordinates for the simulation.
In the following, for simplification of the explanation, the space coordinate that the satellite orbit simulator 2 simulates is 1
Only points are assumed.

The positioning accuracy recording device 3 detects all combinations of any four visible satellites at one time point calculated by the satellite orbit simulator 2 and performs positioning by four GPS satellites of each combination. Accuracy is obtained, and a data table having a data structure as shown in FIG. 2 is created from the result.

In FIG. 2, the "Time" column indicates the observation time, and the "S1", "S2", "S3", and "S4" columns indicate the IDs of the four GPS satellites that make up one combination. And the "DOP" column records the positioning accuracy.
A set of S satellite ID and positioning accuracy is one data set.

There are a plurality of data sets for any one time point. That is, assuming that the number of visible satellites is n, the number of data sets is nC4. Here, C represents a combination Combination. Normally, about 8 GPS satellites are observed from one point on average, so the number of data sets is about 8C4 = 70 on average.

Then, a plurality of data sets for each time point as described above are used for a plurality of time points (simulation period is 1
(If the time interval is 5 minutes, it is 288 time points.) Collectively, and form one data table. The data table actually created by this is, for example, as shown in FIG.

When paying attention to a plurality of spatial coordinates, the above-mentioned data table is created for each spatial coordinate as shown in FIG.

Next, the calculation of the positioning accuracy will be concretely described.

Although there are a plurality of methods of calculating the positioning accuracy, the most general method is DOP (Dolution Of Position).
There is. This DOP is an amount calculated from the direction vector of the GPS satellite used for positioning.

FIG. 5 is a diagram showing a DOP calculation algorithm. In this figure, Azimuth (i), Elevation (i)
The symbol indicates the azimuth and elevation of the i satellite, respectively. This Az
After obtaining imuth (i) and Elevation (i) from the calculation results of the satellite orbit simulator 2, this can be simply ((Ai, Ei), i
= 1, 2, 3, 4) (step ST1). next,
The direction cosine is calculated by the trigonometric function (step ST2), and thereby a 4 × 4 matrix A ′ is created (step ST3). Next, the inverse matrix of A ′ × A is set to B (step ST4).
A DOP is defined as a diagonal element of this B (step ST5). Here, GDOP, HDOP, and VDOP are geometric DOP and horizontal (Horizont), respectively.
al) represents a DOP and a vertical DOP. GNS
In S, these DOPs are used properly according to the flight situation of the aircraft.

When the positioning accuracy recording device 3 completes the creation of the above-described data table, the control device 1 instructs the failure positioning accuracy calculation device 4 to calculate the time probability of the positioning accuracy. Here, the "probability of positioning accuracy over time" is a probability that the accuracy of positioning is smaller than the threshold value by setting a threshold value in the DOP.

In response to this, the positioning accuracy calculation device at the time of failure 4
Performs the calculation of the time probability of positioning accuracy while referring to the data table created and stored in the positioning accuracy recording device 3 in consideration of the failure of the GPS satellite.

Hereinafter, the calculation of the time probability of the positioning accuracy by the failure positioning accuracy calculation device 4 will be described in detail.

First, in GNSS, a combination of four GPS satellites having the smallest DOP at any given time is found, and positioning is performed using the four GPS satellites. Therefore, if the smallest one of the DOPs shown in each of the plurality of data sets for one time point in the data table stored in the positioning accuracy recording device 3 is selected, that DOP is the actual DOP at that time point. Will be equivalent to.

The data table stored in the positioning accuracy recording device 3 serves as information for calculating the time probability of positioning accuracy in consideration of a GPS satellite failure. This is because when the information is retrieved from the data table stored in the positioning accuracy recording device 3, the GPS that is out of order
This is because by ignoring the data set including the satellite ID, the status of positioning by only normal GPS satellites can be grasped. And the ID of the GPS satellite that is out of order
An actual DOP in the failure state can be obtained by obtaining the data set having the smallest DOP from the data sets not including the.

As a result of simplification, it is usual to make an assumption that the failure probability of GPS satellites depends only on the number of failed satellites.

Under this condition, the same coefficient of failure probability is applied when the number of failed satellites is equal. Therefore, the cases where the number of failed satellites is the same are collectively calculated, and the weighted average of the time probabilities of the accuracy is calculated.

As shown below, the accuracy time probability is calculated for each failure satellite number k, and the product sum of the failure probability and the accuracy probability is calculated.

When k = 0, DOP for each time
Only one value of can be obtained. Therefore, the time probability of accuracy for k = 0 is calculated using them.

When k = 1, the control loop is single with respect to the satellite number of the failed satellite, and the variable number of this single control loop is excluded from the set of satellite numbers of the visible satellites to obtain the DOP. calculate. That is, GPS with satellite number "1"
If the satellite is out of order, if the GPS satellite with satellite number "2" is out of order, etc., the satellite numbers of the failed satellites are changed, and the data set including the failed satellite is ignored for each state. One value of DOP will be calculated.

After performing this process for all time points,
The time probability of accuracy is calculated from the result.

When the processing is completed for all IC1 = I, the average probability is calculated by IC1 and the processing for k = 1 is completed. Here, I is the total number of GPS satellites, and I = 24 in the case of the ideal GPS arrangement. Thus, if I = 24, 24 different DOPs are obtained for each time point when k = 1.

The same applies when k = 2. When k = 2, double control is performed. That is, the satellite number of the first failed satellite is fixed, and the satellite numbers of the second failed satellite are changed to "2", "3" .... Then, each time the satellite number of the second failed satellite goes round, the satellite number of the first failed satellite becomes 1
Then, the satellite number of the second failed satellite is changed from "satellite number of the first failed satellite + 1", and the data set including the failed satellite is ignored for each state, and You will need one value.

Then, all IC2 = I (I-1) / 2!
When the process is completed for, calculate the probability by weighted averaging,
The process of k = 2 is completed. Assuming that I = 24, when k = 2, there are 276 DOs for each time point.
P is required.

In general, for k, a k-fold loop is used to generate a fault condition. The DOP is obtained by excluding the number of satellite numbers of visible satellites included in the k-fold control variable at each time point.

These DOPs are used to calculate the accuracy probability of time for k = k.

Then, all ICk = I (I-1) (I-
2) ... (I−k + 1) / k! For the weighted average.

Thereafter, the same calculation is performed until k = K. Here, K is the maximum number of faults generated at a certain time. Since four GPS satellites are required for positioning, normal GP
It is not necessary to consider the situation where there are three or less S satellites. Therefore, K may be set to [I-4] at the maximum. In reality, the maximum number of GPS satellites visible from one point at a time is about 13, so it is sufficient to calculate up to K = 9. Ah Assuming that I = 24, approximately 1.3 million DOPs are required for each time point when k = 9.

In this way, k = 0, 1, 2, 3, ... K
, The time probability of averaged accuracy can be calculated.

The time probability calculated by the failure positioning accuracy calculation device 4 as described above is given to the effectiveness calculation device 5.

The effectiveness calculation device 5 calculates the effectiveness as follows from the time probability calculated by the failure positioning accuracy calculation device 4.

The effectiveness of GNSS is calculated by the product (sum) of the value calculated from the failure probability of GPS satellites and the time probability of accuracy according to the number of failed satellites. For GPS satellites, some assumptions are defined. First, the failure probability is the same for all GPS satellites. Next, it is assumed that the accuracy time probability can be represented by DOP.

Under these assumptions, the effectiveness Ava is Can be expressed as That is, the effectiveness Ava is obtained as the sum of all products of P_k and D_k when k is changed from "0" to "K". Here, k is the number of failed satellites, and k = 0, 1, 2, ..., K. Further, P_k and D_k are time probabilities of the amount calculated from the failure probability and the accuracy represented by DOP when the number of failed satellites is k.

In the simulation, first, a combination regarding the number of failed satellites k is calculated. Once k is determined, P_k is uniquely determined because it is assumed that the failure probabilities of all satellites are the same.

However, since D_k has different flight states with respect to the number of failed satellites k, it is necessary to distinguish each satellite. Therefore, the number of combinations rapidly increases as the number of failed satellites k increases. A combination of individual satellites is calculated for each failed satellite number k. Next, the time probability of accuracy is calculated for each individual combination. The average of these results is calculated, and the accuracy time probability D_ for the number of failed satellites k
Find k.

Now, P_k is obtained by P_k = ICk × A ^(Ik) U ^(k) . Here, ICk is a binomial coefficient as described above. A is the probability that each satellite is not in failure, and U is the probability that each satellite is in failure. A = 1 / (1 + l_mttr / l_mtbf + s_mt
tr / s_mtbf) U = 1-A, respectively. Furthermore, l_mttr, l_mt
bf, s_mttr, and s_mtbf are constants, and mean repair time (Mean TimeTo Repa
ir) is MTTR, Mean Time Between F
If MTail is set to MTBF, it is expressed as l_mttr: long term MTTR l_mtbf: long term MTBF s_mttr: short term MTTR s_mtbf: short term MTBF.

Then, each constant is I = 24 l_mttr = 1 l_mtbf = 124 s_mttr = 36 s_mtbf = 7300 And if P_0 = 0.71493 P_1 = 0.24475 P_2 = 0.03658 P_k is required.

The probability A that each satellite is not broken is 0.97.
Even in the case of 45, in the entire system in which 24 satellites exist independently, the probability that all 24 GPS satellites have not failed is obtained by multiplying the value of P_0 by the accuracy time probability D_0 (<1). It is 493% or less.

As described above, according to the present embodiment, when one simulation is performed, all combinations of four arbitrary visible satellites at each time point are detected, and four combinations of each combination are detected. The positioning accuracy by the visible satellites is obtained, and a data table in which the positioning accuracy is associated with the IDs of the visible satellites included in each combination is created. Then, the actual DOP when any one of the visible satellites is out of order is performed by obtaining the data set having the smallest DOP from the data set that does not include the ID of the out-of-view visible satellite. ing.

As a result, the DOP in all the failure states can be performed only by searching the data table, and it is not necessary to repeat the simulation while changing the setting of the failure state of the visible satellite variously. Therefore, the calculation required for the simulation can be largely omitted, and the total calculation amount can be greatly reduced to, for example, about 1 / 10,000 and the calculation time can be shortened.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the performance calculation target is a system that performs positioning using GPS satellites. However, the present invention is also applied to the case where a performance measurement system uses any artificial satellite other than GPS satellites. it can. Alternatively, the present invention can be applied to a case where a system that performs positioning using a plurality of types of artificial satellites is a target for performance calculation, such as a system that uses a geostationary satellite (GEO) in addition to a GPS satellite. In this case, the failure probabilities of the different kinds of artificial satellites may be different from each other.

In the above embodiment, the DOP is used as the value of the positioning accuracy. However, even if the method of indicating the positioning accuracy by using the direction vector of the satellite observation is used instead of the DOP, it corresponds to the threshold value of the DOP. However, the time probability is calculated with the threshold value and the product sum with the failure probability of the satellite is obtained, which is applicable similarly to the above embodiment.

Further, the failure probability may be obtained in consideration of the operation (maneuver) of the satellite. This only adds a certain amount of correction to the portion corresponding to the failure probability in the effectiveness calculation, and has no effect on the DOP calculation.

Further, the system performance has continuity in addition to the effectiveness, which can also be efficiently calculated by the same method as in the above embodiment.

Besides, various modifications can be made without departing from the scope of the present invention.

[0069]

The system performance calculation apparatus of the present invention simulates the flight conditions of each of a large number of artificial satellites within a predetermined simulation period, and at a predetermined time interval, at a predetermined observation time, a predetermined observation time is determined. Simulating means for detecting all artificial satellites that transmit receivable signals with positionable radio wave performance at the observation points as visible satellites, and calculating the direction of each of the detected visible satellites based on the observation point. And, based on the result of the simulation by this simulation means, while detecting all combinations of a predetermined number of visible satellites at each observation time point, calculate the positioning accuracy by a predetermined number of visible satellites included in each detected combination, The observation time point, the combination of the predetermined number of visible satellites, and the positioning accuracy are associated with each other. Data table creating and storing means for creating and storing a data table in which one set of data for one observation point is stored for each observation point, and all data included in the data table when no failure of the artificial satellite is assumed. At the time of each observation, from among the data sets, and from the remaining data sets excluding the data set including the failed satellite among the data sets included in the data table when assuming the failure of the artificial satellite Positioning accuracy calculating means for obtaining the positioning accuracy under an arbitrary failure condition by detecting the best positioning accuracy, and system performance for calculating the system performance related to the system based on the positioning accuracy calculated by this positioning accuracy calculating means. And a calculation means.

Further, the system performance calculation method of the present invention simulates the respective flight conditions of a large number of artificial satellites such as GPS satellites and geostationary satellites within a predetermined simulation period, and a predetermined predetermined time interval is set. For each observation point, all the artificial satellites that transmit receivable signals with radio performance capable of positioning at a predetermined observation point are detected as visible satellites, and the detected point of each detected visible satellite is used as a reference. Based on the simulation step of calculating the direction and the result of the simulation in this simulation step, all combinations of a predetermined number of visible satellites are detected at each observation time point, and a predetermined number of visible satellites included in each detected combination are detected. Calculate the positioning accuracy by
A data table creating step of creating a data table for each observation point in which a data set in which the combination of the predetermined number of visible satellites and the positioning accuracy are associated with each other is collected, and a case where a failure of the artificial satellite is not assumed Of all the data sets included in the data table, and in the case of assuming a failure of the artificial satellite, the rest of the data sets included in the data table excluding the data set including the failed satellite. The positioning accuracy calculation step of obtaining the positioning accuracy under an arbitrary failure condition by detecting the best positioning accuracy at each observation time point from the data set of, and the positioning accuracy calculated in this positioning accuracy calculation step. A system performance calculation step for calculating system performance for the system based on It was.

As a result, it is possible to eliminate the necessity of repeatedly simulating the flight conditions of a large number of artificial satellites, and to calculate the system performance with a small amount of calculation in a short time. It becomes the calculation method.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing a configuration of a system performance calculation device according to an embodiment of the present invention.

2 is a diagram showing an example of a data structure of a data table created by the positioning accuracy recording device 3 in FIG.

FIG. 3 is a diagram showing a specific example of a data table created by a positioning accuracy recording device 3 in FIG.

FIG. 4 is a diagram showing an example of a data structure of a data table created by the positioning accuracy recording device 3 in FIG. 1 when paying attention to a plurality of spatial coordinates.

FIG. 5 is a diagram showing a DOP (Dolution Of Position) calculation algorithm.

[Explanation of symbols]

1 ... Control device 2 ... Satellite orbit simulator 3 ... Positioning accuracy recording device 4. Faulty positioning accuracy calculation device 5: Effectiveness calculation device

─────────────────────────────────────────────────── --- Continuation of the front page (56) Reference JP-A-8-178649 (JP, A) JP-A-3-156395 (JP, A) JP-A-5-297106 (JP, A) JP-A-6- 265626 (JP, A) JP 8-110374 (JP, A) JP 3-251778 (JP, A) JP 6-3432 (JP, A) JP 7-91976 (JP, A) JP-A-7-24451 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01S 5/00-5/14

Claims (5)

(57) [Claims] 1. A system performance calculation device for calculating system performance for a system that performs positioning based on the reception status of a part of signals transmitted from each of a large number of predetermined artificial satellites, within a predetermined simulation period. Simulates the flight conditions of each of the large number of artificial satellites in, and transmits a receivable signal with radio performance capable of positioning at a predetermined observation point at predetermined observation points at predetermined time intervals. A simulation means for detecting all the artificial satellites as visible satellites and calculating the direction of each of the detected visible satellites based on the observation point, and based on the result of the simulation by the simulation means, a predetermined value is determined at each observation time point. Detected all combinations of visible satellites, and detected each combination Positioning accuracy by a predetermined number of visible satellites included in the space is calculated, and a data table in which one observation point collects a data set that associates the observation time point, the combination of the predetermined number of visible satellites, and the positioning accuracy with the observation table A data table creating / storing means for creating and storing for each point, and a failure of the artificial satellite is assumed from among all data sets included in the data table when the failure of the artificial satellite is not assumed. In this case, from the remaining data sets excluding the data set including the failed satellite among the data sets included in the data table, the best positioning accuracy at each observation time is detected to detect any failure situation. Positioning accuracy calculation means for determining the positioning accuracy in the system, and system performance related to the system based on the positioning accuracy calculated by the positioning accuracy calculation means. A system performance calculation device comprising: a system performance calculation means for calculating 2. The system performance calculation device according to claim 1, wherein the simulation means is capable of simulating the flight conditions of a plurality of types of artificial satellites. 3. A plurality of types of artificial satellites are GPS (Global
Posisioning System) and Geostationary Satellite (GEO:
3. The system performance calculation device according to claim 2, wherein the system performance calculation device is a Geo-Earth Orbital satellite). 4. The system performance calculation device according to claim 1, wherein the system performance calculation means calculates effectiveness as system performance. 5. A system performance calculation method for calculating system performance of a system that performs positioning based on the reception status of a part of signals transmitted from each of a large number of predetermined artificial satellites, within a predetermined simulation period. Simulates the flight conditions of each of the large number of artificial satellites in, and transmits a receivable signal with radio performance capable of positioning at a predetermined observation point at predetermined observation points at predetermined time intervals. Simulate all artificial satellites as visible satellites and calculate the direction of each detected visible satellite based on the observation point, and based on the result of the simulation in this simulation step, at each observation time point. Detects all combinations of a predetermined number of visible satellites and A data table in which the positioning accuracy by a predetermined number of visible satellites included in the alignment is calculated, and a data set in which the observation time point, the combination of the predetermined number of visible satellites, and the positioning accuracy are associated with each other is collected for one observation point is described above. A data table creation step of creating and storing for each observation point, and assuming no failure of the artificial satellite, assume a failure of the artificial satellite from all the data sets included in the data table In this case, from the remaining data sets excluding the data set including the failed satellite among the data sets included in the data table, the best positioning accuracy at each observation time is detected to detect any failure situation. The positioning accuracy calculation step for obtaining the positioning accuracy in the above, and the system related to the system based on the positioning accuracy calculated in this positioning accuracy calculation step And a system performance calculation step of calculating system performance.