The Hyperbolic Radio System in hydrographic surveying Hyperbolic navigation systems are systems designed to provide long-distance positioning information. LORAN C system is operating and provides position information for ships and land vehicles, too. Today, there are some modernization programs called Euro fix, eLoran, which aim to increase the positioning accuracy, high reliability, and independence from satellite navigation systems. The theoretical accuracy of these modern systems is compatible with navigation satellite systems' accuracy.

1. The Hyperbolic Radio System
Student Name:
Class: Fourth Stage
Course Title: Hydroghraphic Surveying
Department: Geomatics ( Surveying )
College of Engineering
Salahaddin University-Erbil
Academic Year 2019-2020
Copyright

2. 1
ABSTRACT
Hyperbolic navigation systems are systems designed to provide long
distance positioning information. LORAN C system is operating and
provides position information for ships and land vehicles, too. Today, there
are some modernization programmes called Eurofix, eLoran, which aim to
increase the positioning accuracy, high reliability, and independence from
satellite navigation systems. Theoretical accuracy of these modern systems
is compatible with navigation satellite systems accuracy.

3. 2
TABLE OF CONTENTS
Abstract 1
Table of Contents 2
introduction 3
Loran C positioning accuracy 4
Loran C hyperbolic navigation systems perspecives 6
Integrated Loran C-DGPS Eurofix 6
eLoran system 7
Conclusion 15
Reference 15

4. 3
Introduction
Hyperbolic navigation systems are designed to provide long distance
positioning information. They have their origin in the third decade of the
twentieth century, when they began the first research study in the
realization of such a system, the precise control of aircraft and ships
motion, besides opportunities of visual orientation. One such system is the
LORAN system (Long Range Navigation), which is a time differential
hyperbolic system. The first series of Loran transmitters (repeaters) was set
to work in 1943; these would further become the hyperbolic system called
LORAN A.
A chain of LORAN A series was composed of a main station (master) and
several secondary stations (slave) located at a distance of 600 nautical
miles from one another, with a range of 800 ... 1200 nautical miles, at
daytime, and 1200 ... 1500 miles, at night time. This system worked until
1980, when it was replaced with the hyperbolic LORAN C system. The
Loran C hyperbolic navigation system is an advanced variant of the Loran
system, being a being a time and phase differential system. The main Main
features of Loran C system are: working frequency 100 KHz; power output
250 ... 400 KW; 1000 nautical miles range of direct wave, and up to 2300
nautical miles range of reflected wave . This system is currently in service
as Loran C1
: chains of stations: the Saudi Arabia northern chain the
China Sea southern chain, the East China Sea chain, the Korean chain,
the Pacific north-western chain, the Russian eastern chain, the Russian
western chain, and the European chains.

5. 4
LORAN C POSITIONING ACCURACY
Loran line of position is a hyperbole which represents the locus of all
points of equal time difference from two Loran transmitters, located the
focal spots of the hyperbole.The Loran point of accuracy depends on the
angle of intersection of the lines of position, and the accuracy with which
they were determined (Fig. 1)
N'
sh1
sh2
emax
N
LP2
LP1
a
Figure 1. The Loran point
The maximum error of the Loran fix is calculated using the ratio:
2 2
1 2 1 2e ec sh sh 2sh shmax cos cosa a   (1)
where:
emax is the maximum error of a Loran fix;
sh1 and sh2 – the errors in determination of Loran lines of position;
a - the angle of intersection of Loran lines of position

6. 5
Table 1. The value of the maximum error of LORAN C fix
The
angle
a [0
]
The
error
point
sh1,sh2
5 cbl
emax
[cbl]
The
error
point
sh1,sh2
4 cbl
emax
[cbl]
The
error
point
sh1,sh2
3 cbl
emax
[cbl]
The
error
point
sh1,sh2
2 cbl
emax
[cbl]
The
error
point
sh1,sh2
1 cbl
emax
[cbl]
0 10 8 6 4 2
1 9,999 7,999 5,999 3,999 1,9999
2 9,998 7,998 5,999 3,999 1,9996
3 9,996 7,997 5,997 3,998 1,9993
4 9,993 7,995 5,996 3,997 1,9987
5 9,990 7,992 5,994 3,996 1,9980
10 9,961 7,969 5,977 3,984 1,9923
15 9,914 7,931 5,948 3,965 1,9828
20 9,848 7,878 5,908 3,939 1,9696
30 9,659 7,727 5,795 3,863 1,9318
40 9,396 7,517 5,638 3,758 1,8793
50 9,063 7,250 5,437 3,625 1,8126
60 8,660 6,928 5,196 3,464 1,7320
70 8,191 6,553 4,914 3,276 1,6383
80 7,660 6,128 4,596 3,064 1,5320
90 7,071 5,656 4,242 2,828 1,4142
Figure 2. The errors of the Loran fix according with the angle of LOP intersection
The errors of the Loran fix depinds on the angle of LOP intersection. The error is
maximum when the LOP intersection angle tends to zero and minimum when the
angle is 90 degrees.

7. 6
LORAN C HYPERBOLIC NAVIGATION SYSTEMS
PERSPECIVES
There are two directions to hyperbolic navigation systems evolution:
integration with other positioning systems; establishing a new,
independent, modernized, system compatible with present – day satellite
navigation systems, which are also in a continuous process of
modernization
Integrated LORAN C - DGPS Eurofix
The European EUROFIX navigation system is a modern integrated system,
encompassing possibilities of the LORAN C hyperbolic system and the
GPS - DGPS differential satellite system. This system is developed in
western Europe where it uses the Loran C chains of transmitters on the
northwestern coasts of Europe, and the chain DGPS transmitters in the
area, ensuring coverage of over 1000 km, with a positioning accuracy
which goes lower than five meters, and with the possibility of determining
the position in three dimensions using information from three satellites
only. The Eurofix system can work as a DGPS system using data from
LORAN C corrected through GPS. Both types of position information may
be received together or separately, to the same receiver : these LORAN C,
and DGPS items of information, which are compared for determining the
ship’s position; there exist the possibility to replace each other in the event
of failure of one of the systems components.

8. 7
eLORAN System
The upgraded eLoran (Enhanced Loran - eLoran) is an international
standard positioning service, in 2D (two dimensions), navigation and time
(Positioning, Navigation, and Timing - PNT), on the frequency of 100 kHz,
for different transport modes and other civilian positioning applications [7].
eLoran is an improved version of hyperbolic navigation system Loran C
answers the requirements of performance, precision, integrity, and
availability necessary for: air navigation during approach to landing;
coastal navigation in intense traffic areas, during the operations of port
entry, in low visibility conditions; land navigation; terrestrial
positioning; telecommunications and other areas (Internet, etc..), by
providing UTC reference time signals, with an accuracy of 50 ns (Table 2).
Table 2. The eLoran system performances
Accuracy Availability Integrity Continuity
0,004-0,01
nm
(8…20 m)
0,999-
0,9999
0,999999
(1x10-7
)
0,999-
0,9999
over 150
sec

9. 8
The eLoran system is a hyperbolic independent system, distinct and at the
same time to complementary the Global Satellite Navigation System
(Global Navigation Sattelite Navigation System-GNSS). The system, still
under observation, will be developed by 2020.
The first eLoran station was built in Anthor, England (540
55'N; 030
15'W).
This station has been transmitting eLoran messages with Group Repetition
Interval (GRI), GRI = 67310s value and delay of emission of 27300 s
value since. The eLoran messages sent by this station are EUROFIX type
messages and contain differential Loran, differential GPS, information, as
well as integrity data with reference to UTC.
The main advantages of the eLoran system are:
- civilian control;
- eLoran signal is not intentionally degraded;
- UTC synchronized transmission by a method which is independent of the
satellite systems method;
- if the eLoran emission source is synchronized with the same UTC time
source as the one of satellite systems, the eLoran signal can be used in
combination with the satellite navigation signal;
- the eLoran signal can be received in areas where the satellite signal has no
coverage;
- sending a signal, in real time (less than 10 sec), about possible damage, or
loss of signal integrity;
- repeatable positioning accuracy is good;

10. 9
- in addition to the Loran C system, teh signal contains a data channel that
provides specific corrections about the state of the system and information
integrity;
- the implementation and maintenance costs are much lower than those of
satellite systems;
- it can be used to provide differential corrections for satellite systems.
The eLoran system ensures safe and low-cost services for
government and private institutions, and also for users in the aviation,
maritime field, by:
- ensuring all the flight phases (take-off, free flight, approching and
landing);
- providing information for eNavigation, including the use of temporary
and permanent means for ensuring maritime navigation (Aids to Navigation
- AtoNs) to mark dangerous water areas;
- identification of land vehicles;
- maintenance and synchronization of telecommunications wired and
wireless.
eLoran is designed as a complete and complex formed off: (Fig. 3) control
centers; broadcasters; monitoring points; eLoran receivers.
Monitoring
points
eLoran
control center
eLoran users :
aviation
marine
terrestrial transport
time service
telecommunications
eLoran
Broadcasting
stations
Monitoring
points
Figure 3. eLoran design

11. 10
eLoran services are provided by a primary center by specialized
applications. Main distributor provides original and accurate eLoran
information under the operational specifications of the Loran C signal.
Specialized applications for aviation, maritime and navy,etc. provide
specific information by eLoran data channel (eg differential eLoran
messages).
eLoran
differential reference
stations
Control center
Monitoring
points
Broadcasting
stations
Naval receivers
eLoran differential corrections
eLoran
main system
eLoran signaleLoran integration signal
differential corrections eLoran signal
eLoran signal
eLoran differential corrections
eLoran integration signal
maritime system
eLoran
eLoran
differential corrections
Figure 4. The eLoran main system
The eLoran signal is a complex signal that contains the following
information: identification data of eLoran transmitter; The Almanac of
eLoran transmitters and of monitoring points; UTC time scale reference;
time difference between the eLoran time and the UTC time;the eLoran
signal; warnings about abnormal radio propagation conditions due to
specific atmospheric conditions; message identifying the emission eLoran
users; differential -satellite corrections.
The eLoran signal for naval users has a circuit for elaboration, evaluation,
verification and updating, which comes from the Main eLoran System and
reaches the eLoran onbord receivers by the Maritime eLoran System. The
eLoran receiver picks up eLoran signal and also the integrity signal of
eLoran data, as well as the eLoran differential corrections.

12. 11
The eLoran signal emission is done automatically. For eLoran signal
modern SSX transmitters (Solid StateTransmitter) are used with continuous
energy sources, equipped with systems of time and frequency
control. The eLoran signal phase corrections are made continuously.
eLoran time is provided by high performance cesium clocks or other
technology of the same accuracy class with them.
Anomalies in the work of eLoran transmitter stations are signaled in a very
short time, as in Loran C system, warning the user not to use eLoran
information until the problem is solved.
The eLoran control centers ensure rapid resolution of faults and provide
conditions for maintenance, continuity, availability of signal in accordance
with the announced performance.
The system’s maintenance is planned in such a way, so as to minimize the
impact on transmitter stations work.
Monitoring points are designed to ensure signal integrity for all users of
eLoran system. The receivers in these points permanently monitor the
eLoran signal quality, throughout the area of responsibility. Some
monitoring stations are used as reference stations to generate eLoran
messages. Also, some monitoring stations will provide real-time
differential corrections for onbord ships receivers, as well as warnings for
aviation.
The eLoran receivers provide acquisition and signal tracking of eLoran
messages received from several eLoran stations, in order indicate a more
accurate positioning and time. Also, the eLoran receivers can ensure the

13. 12
correctness of each eLoran signal alone. The eLoran receivers receive and
decode eLoran messages based on specific applications.
The exchange of information between the eLoran Control Center, eLoran
emmiters, and monitoring points are shown in Fig.5.
eLoran broadcasting stations
-
- /
eLoran control station
- transmite the corrections from the
broadcasting station
-
Monitoring points
-
-
validate the corrections received
from control stations and format
them for transmission
transmit the eLoran signal /
eLoran corrections
validate and stores the corrections
received from monitoring stations
receive the eLoran signals and applies
the necessary corrections to ensure the
integrity of information
receive the eLoran signals and
generates the corrections
Figure 5. The exchange of informations
An eLoran receiver determines its position (latitude and longitude) and
UTC time by measuring the times of receiving impulses from the last three
eLoran stations within its range of visibility.The eLoran signals passing
over various relief forms produce deviations of reception times called
additional secondary factors (Aditional Secundary Factors - ASF) as
compared to theoretical reception times, and hence, decreased accuracy in
the point. However, by using differential information – eLoran the
accuracy is growing ; it becomes very good, of about 10 meters. An ASF
error of 1 s can produce, in time, an error in distance of 300 m. An ASF
chart contains the nominal values of ASF factors for a certain area and for
a specific transmitter.

14. 13
ASF value in μs, depending on the relief forms is as follows:
0.00 - surface of the sea;
1.65 - clay soil;
2.36 - marsh and sea ice;
4.94 - land with shrubs;
6.12 - dry;
6.62 - sand (desert);
The modern integrated eLoran receivers type eLoran – GPS LORADD can
receive signals having the following technical characteristics: individual
reception of an eLoran positioning message; for areas where there are
ASF maps (using ASF corrections) the accuracy of the point increases;
eLoran and GPS combined signal reception; by comparing the two signals,
the positioning accuracy is very good; working power 4 W; 9...36 V DC
voltage; 90% humidity accepted; UTC reference; antenna used: type E - for
eLoran signal reception, type H - for receiving combined eLoran and GPS
signals.
The eLoran applications system are based on minimum operational
performance standards. For aviation, eLoran provides information for
guiding in a horizontal plane and not so much information about latitude,
for all phases of flight (takeoff, free flight, approach and landing).
Maritime eLoran system will provide positioning information and time
with high accuracy, to meet the provisions of IMO Resolution
A.953/23/2003 related to global navigation system (navigation systems
System-Wide World WWRNS). These performance standards apply to the

15. 14
approach and entry into ports, navigation in coastal areas with heavy traffic
and high risk (Table 3).
Table 3. The eLoran performance sdandard
Accuracy Availability
Time
alarm
Confidence
level
10m
(95%)
0,998
over 2
years
10
sec.
0,9997
over 3
ohours
By applying differential - eLoran corrections, in real time, these
performance standard are fulfilled. For time information,the eLoran system
comes under ITU G.811/1997.
In addition, if a suitable antenna is attached to an eLoran receiver this can
be used as a eLoran compass, with which eLoran bearings to the emissions
stations can be measured; also, the ship’s course can be read at a precision
lower than 10
, independent of the ships’s position and movement.
It also envisages coupling the eLoran receivers coupled with ECDIS and
AIS systems.

16. 15
CONCLUSIONS
An eLoran system will also provide the following for the maritime
navigation :
a. enhanced safety: it can be used with high accuracy compared to other
methods and visual navigation aids, as a backup system of a satellite
navigation system;
b. security: provides the functionality of collision warning systems, when
satellite navigation systems, or traffic control systems – VTS are not
working,
c. econony of resources:
- potential reduction in the number of collisions and groundings and hence,
reducing the number of cases of oil pollution;
- assist in monitoring marine pollution;
- potential reduction of cost with the aids to navigation
REFERENCES
[1] ALRS vol. 2 NP 282, 2011/12, Admiralty List of Radio Signals, UKHO
[2] BOŞNEAGU, R., Navigaţia electronică. Navigaţia ortodromică, Editura
DHM, Constanţa, 2013
[3] BOŞNEAGU, R., Navigaţia maritimă, Editura DHM, Constanţa, 2011
[4] NORRIS, A., RADAR and AIS, Integrated Bridge Systems, vol.1, The
Nautical Institute, 2008
[5] NORRIS, A., ECDIS and POSITIONING, Integrated Bridge Systems,
vol. 2, The Nautical Institute, 2010