This document covers GNSS SARPs (Standards and Recommended Practices) and specifications. It defines key terms like accuracy, integrity, continuity, availability and discusses ICAO requirements. It also provides specifications for GPS, GLONASS and SBAS systems, including details on space/time references, frequencies, modulations, power levels and other RF characteristics. The goal is to explain ICAO standards for GNSS and specifications of existing satellite navigation systems to trainees.

1. GNSS SARPS/Requirements & GNSS
Specifications
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2. Topics to be Covered/Objectives
GNSS SARPS
Definitions
Introductions
Accuracy, Integrity, continuity and
Availability
ICAO Requirements
GNSS Specifications
Definitions
Space and Time reference
GPS elements Specification
GPS RF characteristics
GLONASS RF characteristics
SBAS RF characteristics
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3. At the end of this session, trainee will be able to:
Explain ICAO standard and Recommend Practices about
GNSS.
Explain specifications of existing GPS and SBAS.
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4. GNSS SARPS
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5. GNSS SARPs
Definitions
•A single digital bit of the output of a pseudo-random bit sequence.
Chip
• A class of unique codes used by GPS, which exhibit bounded cross-correlation and off-peak auto-
correlation values
Gold Code
•A set of techniques for denying the full accuracy and selecting the level of positioning, velocity and
time accuracy of GPS available to users
Selective Availability
•Bi-binary is known as “Manchester Encoding/Differential Manchester Encoding”. Using this system,
it is the transition of the edge that determines the bit. Bi-binary is known as “Manchester
Encoding/Differential Manchester Encoding”. Using this system, it is the transition of the edge that
determines the bit.
Bi-binary
GNSS SARPs
Definitions
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6. Introduction
GNSS SARPs
• Defined in the Performance-based Navigation (PBN) Manual (Doc 9613)
for a single aircraft and for the total system which includes the signal-in-
space, the airborne equipment and the ability of the aircraft to fly the
desired trajectory
Navigation System Performance Requirements
• Two types of approach and landing operations with vertical guidance
(APV), APV-I and APV-II, use vertical guidance relative to a glide path,
but the facility or navigation system may not satisfy all of the
requirements associated with precision approach. These operations
combine the lateral performance equal to that of an ILS Category I
localizer with different levels of vertical guidance
APV-I/APV-II
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7. Navigational System Performance Parameters
Accuracy
GNSS position error is the difference between the estimated position and the actual position.
For an estimated position at a specific location, the probability should be at least 95 per cent that the position
error is within the accuracy requirement.
However, GNSS errors change over time unlike VOR and ILS.
The orbiting of satellites and the error characteristics of GNSS result in position errors that can change over a
period of hours.
In addition, the accuracy itself (the error bound with 95 per cent probability) changes due to different satellite
geometries.
Since it is not possible to continually measure system accuracy, the implementation of GNSS demands
increased reliance on analysis and characterization of errors.
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8. Integrity
Integrity is a measure of the trust that can be placed in the correctness of the
information supplied by the total system.
Integrity includes the ability of a system to provide timely and valid warnings to the
user (alerts) when the system must not be used for the intended operation (or phase of
flight).
To ensure that the position error is acceptable, an alert limit is defined that represents
the largest position error allowable for a safe operation.
The integrity requirement of the navigation system for a single aircraft to support en-
route, terminal, initial approach, non-precision approach and departure is assumed to
be 1 – 1 × 10–5per hour.
Navigational System Performance Parameters
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9. Continuity of Service :
It is the capability of the system to perform its function without
unscheduled interruptions during the intended operation.
1.Enroute Operations
2.Continuity of service relates to the capability of
the navigation system to provide a navigation
output with the specified accuracy and integrity
throughout the intended operation assuming that
it was available at the start of the operation.
3.The occurrence of navigation system alerts,
either due to rare fault-free performance or to
failures, constitute continuity failures.
4.Since the durations of these operations are
variable, the continuity requirement is specified as
a probability on a per-hour basis.
5.The navigation system continuity requirement for
a single aircraft is 1 – 1 × 10–4 per hour. However,
for satellite based systems, the signal-in-space may
serve a large number of aircraft over a large area
Approach and Landing Operations
1)For approach and landing operations, continuity
of service relates to the capability of the navigation
system to provide a navigation output with the
specified accuracy and integrity during the
approach and landing, given that it was available at
the start of the operation.
2)In this case, the continuity requirement is stated
as a probability for a short exposure time.
3)For GNSS-based APV and Category I approaches,
missed approach is considered a normal operation.
4)Since it occurs whenever the aircraft descends to
the decision altitude for the approach and the pilot
is unable to continue with visual reference.
Navigational System Performance Parameters
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10. Availability
Characterized by the portion of time the system is to be used for navigation.
When establishing the availability requirements for GNSS, the desired level of service to be
supported should be considered.
Where GNSS availability is low, it is still possible to use the satellite navigation service by
restricting the navigation operating times to those periods when it is predicted to be available.
Specific availability requirements for an area should be based on following for Approach and En-
route
Approach En-route
Traffic density and complexity Traffic density and complexity
Procedures for filing and conducting an approach to
an alternate airport
Alternate navigation aids
Navigation system to be used for an alternate
airport
Primary/secondary surveillance coverage
Air traffic and pilot procedures Air traffic and pilot procedures
Duration of outages Duration of outages
Geographic extent of outages
Navigational System Performance Parameters
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11. ICAO Signal-in-Space Performance Requirements
Annex 10 — Aeronautical Communications (Volume I)
Typical operation
Accuracy
horizontal
95%
Accuracy
vertical
95%
Integrity
Time-
to-alert
Continuity Availability
En-route
3.7 km
(2.0 NM)
N/A
1 – 1 × 10–7/h
5
5 min
1 – 1 × 10–4/h
to 1 – 1 × 10–8/h
0.99 to
0.99999
En-route, Terminal
0.74 km
(0.4 NM)
N/A
1 – 1 × 10–7/h
5
15 s
1 – 1 × 10–4/h
to 1 – 1 × 10–8/h
0.99 to
0.99999
Initial approach,
Intermediate approach,
Non-precision approach(NPA),
Departure
220 m
(720 ft)
N/A
1 – 1 × 10–7/h
5
10 s
1 – 1 × 10-4/h
to 1 – 1 × 10–8/h
0.99 to
0.99999
Approach operations with vertical
guidance
(APV-I)
16.0 m
(52 ft)
20 m
(66 ft)
1 – 2 × 10–7
in any
approach
10 s
1 – 8 × 10–6
per 15 s
0.99 to
0.99999
Approach operations with vertical
guidance
(APV-II)
16.0 m
(52 ft)
8.0 m
(26 ft)
1 – 2 × 10–7
in any
approach
6 s
1 – 8 × 10–6
per 15 s
0.99 to
0.99999
Category I precision approach
16.0 m
(52 ft)
6.0 m to
4.0 m
(20 ft to
13 ft)
1 – 2 × 10–7
in any
approach
6 s
1 – 8 × 10–6
per 15 s
0.99 to
0.99999
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12. ICAO Specified Alert limits
Typical operation Horizontal alert limit Vertical alert limit
En-route (oceanic/continental low density)
7.4 km (4 NM) N/A
En-route (continental)
3.7 km (2 NM) N/A
En-route, Terminal
1.85 km (1 NM) N/A
NPA
556 m (0.3 NM) N/A
APV-I
40 m(130 ft) 50 m(164 ft)
APV- II
40 m (130 ft) 20.0 m (66 ft)
Category I precision approach
40 m (130 ft) 35.0 m to 10.0 m (115 ft to 33 ft)
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13. GNSS Specifications
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14. GNSS SARPs
Definitions
The difference between the true position and the position determined by the GNSS
receiver.
GNSS position error
The specified level of positioning, velocity and timing accuracy that is available to any
global positioning system (GPS) user on a continuous, worldwide basis.
Standard positioning service (SPS)
The maximum allowable time elapsed from the onset of the navigation system being out
of tolerance until the equipment enunciates the alert.
Time-to-alert
Channel of standard accuracy (CSA)
GNSS SARPs
Definitions
The specified level of positioning, velocity and timing accuracy that is available toany
GLONASS user on a continuous, worldwide basis.
Channel of standard accuracy (CSA)
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15. Space and Time Reference
Space Reference
• The position information provided by the GNSS to the
user shall be expressed in terms of the World Geodetic
System — 1984 (WGS-84) geodetic reference datum.
• Note 1— SARPs for WGS-84 are contained in Annex 4,
Chapter 2, Annex 11, Chapter 2, Annex 14, Volumes I
and II, Chapter 2 and Annex 15, Chapter 3.
• Note 2— If GNSS elements using other than WGS-84
coordinates are employed, appropriate conversion
parameters are to be applied.
Time Reference
• The time data provided by the GNSS to the user shall be
expressed in a time scale that takes the Universal Time
Coordinated (UTC) as reference.
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16. GPS Elements Specifications
Space and control segment accuracy
1) Time transfer accuracy
2) Range domain accuracy
Availability
Reliability
Coverage: The GPS SPS shall cover the
surface of earth up to an altitude of
3000kms.
Radio frequency characteristics
GPS Satellites Navigation
Information
Satellite time of transmission
Satellite position
Satellite health
Satellite clock correction
Propagation delay effects
GPS Specifications and Satellite Navigation Information
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17. Parameters Specifications
Carrier frequency 1575.42 MHz(GPS L1) using CDMA
Signal spectrum & BW ±12 MHz band centered on the L1 frequency
Signal power level Each GPS satellite shall broadcast SPS navigation signals with
sufficient power at an elevation angle of 5 degrees fm –
158.5 dBW to –153 dBW .
Minimum elevation angle 5 degrees
Polarization RHCP(clock wise)
Modulation. L1 BPSK modulated with PRN,1.023 MHz Coarse Acquisition
(C/A )code. The C/A code sequence shall be repeated each
millisecond. The transmitted PRN code sequence shall be the
Modulo-2 Addition of a 50 bit navigation message with and
C/A code.
Coordinate system WGS 84
GPS RF Characteristics
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18. GLONASS RF Characteristics
Parameters Specifications
Carrier frequency 1.6 GHz(GLONASS L1) using FDMA
Signal spectrum
& BW
±5.75 MHz band centered on each GLONASS frequency
Signal power level Each GPS satellite shall broadcast SPS navigation signals with
sufficient power at an elevation angle of 5 degrees fm –161
dBW to –155 dBW .
Minimum elevation angle 5 degrees
Polarization RHCP(clock wise)
Modulation. BPSK
Modulo-2 addition of the following three
binary signals:
a) ranging code transmitted at 511 kbits/s;
b) navigation message transmitted at 50 bits/s; and
c) 100 Hz auxiliary meander sequence.
Coordinate PZ-90
GT
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19. SBAS RF characteristics
Parameters Specifications
Carrier frequency 1 575.42 MHz(GPS L1) using CDMA
Signal spectrum & BW ±12 MHz band centered on the L1 frequency
Signal power level Each SBAS satellite shall broadcast navigation signals with
sufficient power at an elevation angle of 5 degrees from –
161 dBW to –153 dBW .
Minimum elevation angle 5 degrees
Polarization RHCP(clock wise)
Modulation. The transmitted sequence shall be the Modulo-2 Addition of
the navigation message at a rate of 500 symbols/sec and C/A
code. It shall then be BPSK modulated onto the L1 carrier at a
rate of 1.023 Mps
SBAS Network time Difference between SNT and GPS time shall not exceed 50
nanoseconds
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20. Questions?
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21. Thank You
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