299
1 INTRODUCTION
Air transport is one of the regular modes of transport
and it is therefore essential that it be as safe as
possible. The intensive development of aviation,
which occurred after the Second World War, led to an
increase in capacity and a reduction in air traffic. At
the same time, this caused an increase in more
frequent collisions of aircraft in the air. For this
reason, it was necessary to develop a system that
would increase air safety and help prevent such
collisions. Several types of anti-collision systems have
been developed in the history of aviation. Significant
progress in their development did not come until
1981. At this time, the currently best-known active on-
board anti-collision system TCAS (Traffic Alert and
Collision Avoidance System) was improved. The
development of this system continues today even
today due to the ever-increasing demands on air
safety. TCAS means additional safety insurance in air
traffic. There are also financially and technically less
demanding anti-collision systems, such as the PCAS
system, the so-called mobile anti-collision system.
Thanks to its specific properties, this passive system is
also suitable for its installation in smaller aircraft and,
due to its financial availability, it is intended mainly
for the needs of general aviation. Anti-collision
systems are currently a key element in increasing the
level of air safety. In our research we have devoted the
alternative possibility of determining the position of
aircraft without the use of satellite navigation systems,
based on the principles of relative navigation
(RelNav). In order for this method of navigation to be
applicable, it is necessary to analyze the accuracy of
the system and its application within the concept of
the future communication and navigation
infrastructure. The main goal of the paper is to
evaluate the accuracy of position determination by the
RelNav system depending on the position of users of
the communication network. Work related to relative
navigation is focused on research in formation flights,
in-flight refueling and initial navigation, which is
directly dependent on GNSS. Currently, relative
navigation is most important for mapping and
navigating UAV resources in a GNSS-free
environment. We published the results of the
evaluation of the accuracy of the relative navigation
system in [24]. The results of the simulation of the
Influence of Mutual Position of Communication
Network Users on Accuracy of Positioning by Telemetry
Method
M. Džunda & P. Dzurovčin
Technical University of Kosice, Kosice, Slovakia
ABSTRACT: In this paper we solve the problem of the influence of the mutual position of the users of the
communication network on the accuracy of the telemetric navigation system. We present the principle of
operation of a telemetry navigation system and examine the accuracy of determining the position of users of the
communication network depending on their mutual position. The telemetric method of determining the
position of users of a communication network can be used in shipping or air transport. The simulation of the
telemetry system will be performed in the Matlab software environment.
http://www.transnav.eu
the International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 15
Number 2
June 2021
DOI: 10.12716/1001.15.02.04
300
RelNav system presented in these works confirm that
the accuracy of this system deteriorates as the distance
between the users of the communication network
increases. We have also found that the accuracy of the
RelNav system depends on the relative position of the
users of the communication network. The [6] work
presents a method improve DME distance measuring
accuracy by using a new DME pulse shape. The
proposed pulse shape was developed by using
Genetic Algorithms and is less susceptible to
multipath effects so that the ranging error reduces by
36.077.3% when compared to the Gaussian and
Smoothed Concave Polygon DME pulses, depending
on noise environment. The [5] paper introduces
optimal ground station augmentation algorithms that
help to efficiently transform the current DME ground
network to enable a DME/DME positioning accuracy
of up to 0.3 nm or 92.6 m with a minimal number of
new ground DME sites. The positioning performance
and augmented ground network using the proposed
Stretched-Front-Leg (SFOL) pulse-based DME are
evaluated in two regions which have distinct terrain
conditions. The [10] Distance Measuring Equipment
(DME) is seeing renewed interest for its ability to
support future aviation navigation and surveillance
needs. It is one of the major technologies being
examined by the FAA Alternative Position Navigation
and Timing (APNT) program to support needs to
provide an alternative to GNSS in a NextGen airspace.
Facility data-base resolution and fidelity, and
precision of DME ground system location surveys are
a function of today's 0.2 nm system error limit. These
errors become noticeable when viewing flight data
that is processed to the tighter tolerances required by
APNT. Their contribution to system error will likely
require reduction [1]. The navigation subsystem in
most platforms is based on an inertial navigation
system (INS). Regardless of the INS grade, its
navigation solution drifts in time. To avoid such a
drift, the INS is fused with external sensor
measurements such as a global navigation satellite
system (GNSS). In situations when maneuvering helps
to improve state observability, virtual lever-arm
(VLA) measurements manage to gain additional
improvement in accuracy. These results are supported
by simulation and field experiments with a vehicle
mounted with a GNSS and an INS [8]. Positioning
accuracy of area navigation (RNAV) is directly related
to geometric dilution of precision (GDOP). For the
distribution of three DME beacons, this paper
establishes the GDOP algorithm model based on
DME/DME RNAV, the GDOP calculation is deduced,
and the relation between GDOP and DME ground
station distribution is given. The affection of the
geometric configuration and the baseline length of
DME stations, and of the aircraft height on GDOP
values are studied and simulated by MATLAB. In [7]
the optimal methods of DME beacon distribution for
DME/DME RNAV are proposed and all these results
will provide theoretical guidance for implementation
of DME/DME RNAV in China. Alternative
positioning navigation by DME service network is
used in many cases on-board of aircraft. This problem
is topical in case of bad accuracy of GNNS, spatially
during takeoff or landing phases of aircraft flight. In
the paper, an accurate approach of positioning by data
from DME with support of all available DMEs signals
in particular point of airspace has been discussed. An
availability area of Ukrainian DME service network
for altitude of FL320 has been evaluated. Dilution of
precision coefficient for geometrical factor estimation
in accuracy calculation of positioning by DME
network for Ukrainian airspace was used [13]. A
typical type of a DME pulse being used in practice is a
Gaussian pulse, and the achievable DME ranging
accuracy is primarily determined by the pulse shape.
[Kim, E. 2013] presents an alternative DME pulse
waveform that is able to provide much higher range
accuracy than the conventional Gaussian pulse. The
alternative pulse waveform is compliant with the
pulse shape requirements in the current DME
specifications to maintain the compatibility with
existing DME ground transponders and avionics. In
addition, the paper discuss the potential constraints in
implementing the alternative pulse in the existing
transponders and avionics. The Multi-constellation
Global Navigation Satellite System (Multi-GNSS) has
become the standard implementation of high accuracy
positioning and navigation applications. It is well
known that the noise of code and phase
measurements depend on GNSS constellation. Then,
Helmert variance component estimation (HVCE) is
usually used to adjust the contributions of different
GNSS constellations by determining their individual
variances of unit weight. However, HVCE requires a
heavy computation load [12]. [Zhao, J. et. Aall 2018]
presents a new method to improve the accuracy in the
heading angle estimate provided by low-cost
magnetometers on board of small Unmanned Aerial
Vehicles (UAVs). This task can be achieved by
estimating the systematic error produced by the
magnetic fields generated by onboard electric
equipment. The magnetic biases’ determination
problem can be formulated as a system of non-linear
equations by exploiting the acquired visual and GNSS
data [19]. The Chinese Area Positioning System
(CAPS) is a new positioning system developed by the
Chinese Academy of Sciences based on the
communication satellites in geosynchronous orbit.
The CAPS has been regarded as a pilot system to test
the new technology for the design, construction and
update of the BeiDou Navigation Satellite System
(BDS). BDS-3 type is equipped with two major
functions, namely navigation and positioning, as well
as data communication. BDS can provide seven types
of services. The results indicate a potential application
of CAPS for highly accurate positioning and speed
estimation and the availability of a new navigation
mode based on communication satellites [16]. At the
same time, many applications do not require precise
absolute Earth coordinates, but instead, inferring the
geometric configuration information of the
constituent nodes in the system by relative
positioning. The Real-Time Kinematic (RTK)
technique shows its efficiency and accuracy in
calculating the relative position. The efficiency test
shows that the proposed method can be a real-time
method, the time that calculates one epoch of
measurement data is no more than 80 ms and is less
than 10 ms for best results. The novel method can be
used as a more robust and accurate ambiguity free
tracking approach for outdoor applications [15]. To
bridge the GPS outage for multicopters is designed
proposes a novel navigation reconstruction method
for small multicopters, which combines the vehicle
dynamic model and micro-electro-mechanical system
301
(MEMS) sensors. Firstly, an induced drag model is
introduced into the dynamic model of the vehicle, and
an efficient online parameter identification method is
designed to estimate the model parameters quickly. In
addition, the nongravitational acceleration estimated
from body velocity and radar height are utilized to
yield a more accurate attitude estimate. Some types of
Multi-Static Surveillance Radars are described in [17-
18]. Fusing the information of the attitude, body
velocity, magnetic heading, and radar height, a
navigation system based on an error-state Kalman
filter is reconstructed. Simulation results show that
the proposed navigation reconstruction algorithm
aided by the vehicle model can significantly improve
navigation accuracy during a GPS outage [14]. This
article demonstrates the superiority of a fuzzy
tracking system over the standard Kalman filter
tracking system under the conditions of uneven
accelerations and sudden change of direction of the
targets, as well as in the case of failure to observe the
target during successive scans. A cascading Kalman
filtering algorithm was used to solve the speed
ambiguity and to reduce the measurement error in
real-time radar processing. The cascade filters are
extended Kalman filters with controlled gain using
fuzzy logic for tracking targets using radar equipment
under difficult tracking conditions [11]. An automatic
landing of an unmanned aerial vehicle (UAV) is a
non-trivial task requiring a solution of a variety of
technical and computational problems. The most
important is the precise determination of altitude,
especially at the final stage of approaching to the
earth. With current altimeters, the magnitude of
measurement errors at the final phase of the descent
may be unacceptably high for constructing an
algorithm for controlling the landing manoeuvre. One
of the possible and straightforward ways is the
camera resolution change by pixels averaging in
computer part which performed in coordination with
theoretically estimated and measured OF velocity.
The article presents results of such algorithms testing
from real video sequences obtained in flights with
different approaches to the runway with simultaneous
recording of telemetry and video data [9]. Over the
past years Time-of-Flight (ToF) sensors have become a
considerable alternative to conventional distance
sensing techniques like laser scanners or image based
stereo-vision. Due to the ability to provide full-range
distance information at high frame-rates, ToF sensors
achieve a significant impact onto current research
areas like online object recognition, collision
prevention or scene and object reconstruction. The
main contribution, in this context, is a new intensity-
based calibration model that requires less input data
compared to other models and thus significantly
contributes to the reduction of calibration data.
2 POSITIONING BY TELEMETRY METHOD
The principle of the telemetric method is described in
detail in [4]. Next, in accordance with [4], we will state
algorithms for calculating the flying object position.
Telemetry is the automatic measurement and wireless
transmission of data from remote sources. The
location of the FO is determined by acquiring the
transmissions from three (or more) different locations
to triangulate the location of the device. Each user in
communication network transmits a signal which
contains information about its position and the
current time at regular intervals. These signals,
travelling at the speed of light, are intercepted by a
receiver of an unknown user, which calculates how far
each user is based and how long it takes for the signal
to arrive. The range from the other users is
determined by the time the signal is received. To
ensure the work of the RelNav system, at least three
users must be visible to the unknown receiver at all
times. The location of the unknown user is calculated
by the following solution system of three equations
[4]:
( ) ( ) ( )
2 2 2
i i i i
x x y y z z d + + =
(1)
where: xi, yi, zi- geocentric coordination of the user, di
range between an unknown receiver and each
transmitter, x, y, z- geocentric coordination of an
unknown receiver.
The distances to the users are derived from the
transmitted signals and they are affected by
uncertainties in clock setting, therefore they are
normally referred to as pseudo-ranges. There is a time
synchronization problem of each user´s clock. The
Pseudo-range measurements lead to a pseudo-ranging
four point problem which is the problem of
determining the four unknowns. The unknowns
comprise the three components of the receiver
position {X, Y, Z} and the stationary receiver range
bias. Four pseudo-range equations are expressed
algebraically as [4]:
(2)
( ) ( ) ( ) ( )
2 2 2 2
2 2 2 2
0x x y y z z b d + + =
(3)
( ) ( ) ( ) ( )
2 2 2 2
3 3 3 3
0x x y y z z b d + + =
(4)
( ) ( ) ( ) ( )
2 2 2 2
4 4 4 4
0x x y y z z b d + + =
(5)
where: d1, d2, d3, d4 measured pseudo-distances
from a source of transmission to receivers, x1-4, y1-4, z1-4
coordinates of users, x, y, z- coordinates of the
receiver, b shift of the time basis of the receiver
converted into distance.
For subtraction (5) from (2), is valid:
14 14 14 14 41 14
f x x y y z z d b e= + + + +
(6)
For subtraction (5) from (3), is valid it holds:
24 24 24 24 42 24
f x x y y z z d b e= + + + +
(7)
For subtraction (5) from (4), is valid:
34 34 34 34 43 34
f x x y y z z d b e= + + + +
(8)
302
If variable b is considered as constant (the so-called
factor of homogenization), then, depending on
expressions (6-8), a system of three equations with
three unknown variables is obtained. We have applied
the method of resultants of the multi-polynomials to
solve the system of linear equations x=g(b), y=g(b),
z=g(b) [4].
Following is valid:
( )
1 14 41 14 14 14
f x x d b e k y y z z= + + + +
(9)
( )
2 24 42 24 24 24
f x x d b e k y y z z= + + + +
(10)
( )
3 34 43 34 34 34
f x x d b e k y y z z= + + + +
(11)
If the variable “k“ turns into the factor of
homogenization, Jacobi’s determinant of the
coordinate x by (9), (10), (11) is expressed as:
11
1
22
2
3 3 3
det
x
df df
df
dy dz
dk
df df
df
J det
dy dz
dk
df df df
dy dz dk




==





(12)
In compliance with (9-11), for y = g (b) is valid:
( )
4 14 41 14 14 14
f y y d b e k x x z z= + + + +
(13)
( )
5 24 42 24 24 24
f y y d b e k x x z z= + + + +
(14)
( )
6 34 43 34 34 34
f y y d b e k x x z z= + + + +
(15)
Jacobi’s determinant for the coordinate y is
expressed as:
4 4 4
5 5 5
6 6 6
y
df df df
dx dz dk
df df df
J det det
dx dz dk
df df df
dx dz dk




==





(16)
In compliance with (9-11), for z = g (b) is valid:
( )
7 14 41 14 14 14
f z z d b e k x x y y= + + + +
(17)
( )
8 24 42 24 24 24
f z z d b e k x x y y= + + + +
(18)
( )
9 34 43 34 34 34
f z z d b e k x x y y= + + + +
(19)
Jacobi´s determinant for coordinate z is expressed
as:
77
7
88
8
9 9 9
z
df df
df
dx dy
dk
df df
df
J det det
dx dy
dk
df df df
dx dy dk




==





(20)
From expressions (12), (16), (20) we obtain the
value of the determinants Jx, Jy, Jz. We get the variable
equations x=g(b), y=g(b), z=g(b) by applying the value
of each determinant. Substituting the expression for x,
y, z into the equation (2), the quadratic function for
the unknown variable b is obtained:
22
0Ab Bb C+ + =
(21)
Solutions of the quadratic equation (21) have two
roots, b+ and b-. Therefore we have to calculate the
coordinates of the FO (x+, y+, z+) and P (x-, y-, z-). To
come to the correct solution, we have to calculate the
norm (
2 2 2
norm x y z= + +
) for (x, y, z) b- and (x, y, z)
b+. If the coordinates of the receiver are fed into the
coordinate reference system, the norm of the position
vector will be close to the value of the radius of the
Earth (Re = 6372.797 km) and this solution for the FO
(x, y, z) will be regarded as a correct one [4].
2.1 Evaluation of the influence of users location on the
accuracy of the RelNav system
In accordance with algorithms 1 to 21, we performed
evaluation of the influence of users location on the
accuracy of the RelNav system. Using simulation, we
investigate the effect of the geometric distribution of
flying objects on the accuracy of determining their
position. The test cases are designed to examine the
sensitivity of the relative navigation system to this
factor.The simulation results are shown in figure 1 to
5.
In our simulation, we assume that LOT5MF is a
flying object whose position we want to determine.
We know the coordinates FO RJA39K, FHM6112,
LOT653 and WZZ3007. It is clear from the theory of
navigation that the accuracy of determining the
position of the FO rangefinder method depends on
the accuracy of measuring the distance from own
rangefinders to the rangefinders of the others systems
and on the geometry of the rangefinder systems.
Therefore, we checked how the accuracy of the
RelNav system will depend on the FO geometries
working in the aviation communication network. We
performed further simulations and investigated the
accuracy of FO positioning when changing the
geometry of communication network users. The
simulations were performed for a straight flight
lasting 1375 s. When selecting the geometry of users of
the aviation communication network, we proceeded
as follows. We will consider FO LOT5MF as an
unknown FO. The initial positions of the LO in the
simulation for a distance of 5 km are shown in Figure
no. 1 and in table no. 1 and 2. When selecting the
initial coordinates of the network users, we placed the
individual users with respect to the geographical
course of the LOT5MF flight. The geographical course
303
of the LOT5MF flight will be 345 for all simulations.
The geographic course of the initial position of the
user of the RJA39K communication network will be
48. The geographic course of the initial position of the
user of the communication network FHM6112 will be
19. The geographic rate of the initial position of the
user of the LOT653 communication network will be
318. The geographic course of the initial position of
the user of the communication network WZZ3007 will
be 286. In the individual simulations, we gradually
changed the distances between LOT5MF and users
RJA39K, FHM6112, LOT653 and WZZ3007 in the
range of 5 to 50 km. The initial positions of the LO in
the simulation for a distance of 5 km are shown in
Figure no. 1 and in table no. 1 and 2.
Table 1. Initial LO coordinates in the WGS-84 system and in
the coordinate system ECEF, distance 5 km
_______________________________________________
FO identification latitude (°) longitude (°)
_______________________________________________
1. RJA39K 48.8022 21.1971
2. FHM612 48.8143 21.1657
3. LOT653 48.8080 21.1097
4. WZZ3007 48.7856 21.0838
5. LOT5MF 48.771 21.148
_______________________________________________
latitude (rad) longitude (rad) height above sea level
_______________________________________________
1. 0.851759 0.369959 11262
2. 0.851970 0.369411 10683
3. 0.851860 0.368433 7003
4. 0.851469 0.367982 10363
5. 0.851215 0.369102 3784
_______________________________________________
X (km) Y (km) Z (km)
_______________________________________________
1. 3931.154 1524.565 4784.573
2. 3930.688 1521.907 4785.025
3. 3930.405 1517.382 4781.793
4. 3934.907 1517.076 4782.678
5. 3930.301 1520.361 4776.659
_______________________________________________
Picture no. 1 shows the distribution of FO1-4 users
with respect to FO5 for a distance of 5 km. The initial
coordinates of the FO are marked with a black (+)
sign, which indicates the identification mark of the
individual FO.
Figure 1. Flight trajectories of five FO, straight flight, shift 5
km, flight length 1375 s.
The results of the FO positioning simulation are
shown in FIG. 2 to 5. In FIG. no. 2 shows the errors of
measuring the distance ∆d1 to ∆d4 between LOT5MF
and other network users as a function of time. From
picture no. 2 shows that the mean values of the
distance measurement errors ∆d1 to ∆d4 range from -
0.03 m to 0.02 m and the dispersions of the distance
measurement errors ∆d1 to ∆d4 range from 0.98 m
2
to
1.01 m
2
.
Figure 2. Errors in measuring the distance ∆d1 to ∆d4
between LOT5MF and other network users.
In FIG. no. 3 shows the error of determining the
coordinates ∆X, ∆Y, ∆Z and the error of determining
the position FO5 ∆P as a function of time. From
picture no. 3 shows that the mean values of the
coordinate errors ∆X, ∆Y, ∆Z range from - 0.03 m to
0.06 m and the dispersion of coordinate errors ∆X, ∆Y,
∆Z ranges from 2.81 m2 to 9.80 m2. The mean value of
the positioning error FO 5 m∆P is equal to 3.84 m and
the dispersion of the positioning error FO 5 2∆P is
equal to 6.04 m2.
Figure 3. Coordinate determination errors ∆X, ∆Y, ∆Z and
position error ∆P FO5, rectilinear flight 1375 s
In picture no. 4 is a histogram of the positioning
error LO 5. It can be seen from the figure that the
maximum number of positioning errors is in the range
of 0.8 to 7.64 m.
In order to verify the sensitivity of the derived
algorithm to the accuracy of FO 5 positioning, which
works in the aviation communication network, we
performed additional simulations. We maintained the
initial coordinates of FO RJA39K, FHM6112, LOT653
and WZZ3007 in the above courses and changed their
304
distances from LOT5MF in the range of 10 to 50 km.
The results of the simulation when changing the
distances of FO 5 from other FO 1 to 4 from 5 to 50 km
are shown in Figure no. 5. From picture no. 5 shows
that the mean value of the positioning error FO 5 mP
was in the range of 3.5 to 10.0 m and the dispersion of
the positioning error FO 5
2
P varied in the range of
7.0 to 72.79 m
2
. From picture no. 5 shows that as the
distances FO RJA39K, FHM6112, LOT653 and
WZZ3007 from LOT5MF increase, the positioning
errors increase. Based on this, we can conclude that
the accuracy of determining the position of a flying
object operating in the aviation communication
network depends on the mutual position of network
users. Our proposed RelNav system is accurate. The
subject of further research will be the dependence of
the accuracy of this system on the mutual position of
the users of the communication network. vv
Figure 4. FO5 positioning error histogram
Figure 5. LO 5 positioning accuracy for straight flight and
distances from 5 to 50 km.
3 CONCLUSION
Using derived algorithms and a model of the motion
of flying objects, we performed a computer
simulation, which is used to determine the position of
the unknown LO 5 and evaluate the accuracy of the
proposed system RelNav. The computer simulation
was performed in the Matlab programming
environment and explains the principle of operation
of the RelNav system. The result of modeling is a total
of five models that simulate the motion of LO in a
geocentric coordinate system. A description of the
models is given in [4]. LO motion models represent
input data for computer simulation. In order for the
simulation to correspond to reality as much as
possible, we performed observations of air traffic over
the territory of the Slovak Republic via the
Flightradar24 application. We randomly selected five
FOs, whose geographical coordinates and heights we
implemented in our model. For the needs of solving
the problem, it was necessary to transform the
coordinates into a geocentric coordinate system. The
result of the simulation is the evaluation of the
accuracy of determining the position of FO 5 for
different model situations. The simulation results
confirmed that the accuracy of FO position
determination in the RelNav system depends on the
geometry of the communication network users. The
principles of relative navigation can also be applied to
maritime 2D navigation. The basic condition for the
correct operation of such a system in the navy is to
create a communication network of users and to
ensure time synchronization of data transmission by
individual users. We assume that for the accuracy of
determining the location of the user of this network
will be the same as for the aviation communication
network. In further research, it would be appropriate
to verify the navigation possibilities of flying and
floating objects (ships) in the relative navigation
system.
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