NAVIGATION – method of determining the – By 1993, the 24 (now 31) satellites that

position and direction during travel made up the system were fully operational
– currently has 31 operational satellites in
orbit, though only 24 are needed for full
TWO PRIMARY CATEGORIES OF global coverage.
NAVIGATION
GLONASS
PMW – PHYSICAL MODEL-BASED
– stands for Globalnaya Navigazionnaya
METHODS
Sputnikovaya Sistema, which translates to
–It measures rotation and acceleration
Global Navigation Satellite System
using accelerometer and gyroscopes and uses
– was developed by the Soviet Union (now
this information to calculate its movement and
operated by Russia) in the 1970s
position relative to the starting point.
– by December 2011, it became fully
Ex: Inertial Navigation Systems (INS)
operational with a complete constellation of
EDM – EXTERNAL DATA-BASED 24 satellites, providing global coverage
METHODS similar to GPS.
– use information from external systems
BeiDou Navigation Satellite System or BDS
and data models like from satellites and local
beacons to enhance the accuracy and efficiency – Big Dipper Constellation, also known as
of the navigation. Běidǒu in Chinese
Ex: Global Navigation Satellite Systems – 1994: Development of the BDS begins in
(GNSS) China
– 2000: The first BeiDou satellite is launched
– 2012: BeiDou started to provide services to
GLOBAL NAVIGATION SATELLITE the Asia-Pacific region
SYSTEM(GNSS) – 2018: BeiDou system launched its basic
global service
– is a network of satellites that provides precise
– 2021: officially announced as being
location and time information to receivers on
available worldwide with 44 active satellites
Earth by transmitting radio signals, allowing
global positioning and navigation. Galileo
Examples of GNSS and RNSS: – named after the famous Italian astronomer
GPS, GLONASS, BeiDou, Galileo, NavIC, and physicist Galileo Galilei
QZSS – developed by European Union and the
European Space Agency (ESA) in 2001
– 2005: The first Galileo test satellite,
HISTORY GIOVE-A, is launched
– 2020: The Galileo system is officially
Global Positioning System (GPS) declared operational with 26 satellites in
– first satellite-based navigation. orbit
– Developed by US in 1970s for military – As of now, it has 30 (24 active + 6 spares)
navigation and targeting purposes satellites
– The first Navigation System with Timing Navigation with Indian Constellation or
and Ranging (NAVSTAR) satellite was NavIC
launched in 1978.
 – also known as Indian Regional Navigation – The use of fourth satellite to calculate time
Satellite System (IRNSS) offset (the clock error)
– developed by India started in 2006
Satellite Triangulation or Trilateration
– first satellite was launched in 2013
– by 2018, it completed the 7 constellations With synchronized time, three satellites
– by 2020, NavIC becomes operational, provide enough data to calculate latitude,
providing regional navigation services with longitude, and altitude, as each satellite’s
improved accuracy signal forms a sphere with the satellite at the
center. The intersection of these spheres
Quasi-Zenith Satellite System (QZSS)
pinpoints the receiver’s location in 3D space.
– 2002, it was first developed by Japan to
improve performance and availability of
satellite navigation in canyons and
mountainous area in the region
– First launch started in 2010 (Michibiki-1)
– By 2018, four-satellite constellation was
completed
– 7 constellation is expected to be established
from 2024 to 2025

GNSS COMPONENTS
Control Segment: ground-based stations that
monitor, maintain, and control the GNSS
satellites
Space Segment: satellites themselves which
sends signal from space orbiting the Earth at
Radio Wave Propagation in GNSS Systems:
high altitudes
Ionospheric and Tropospheric Effects
Space Segment: consists of the GPS receivers
High concentration of ionized particles in
and the user community
ionosphere causes refraction and dispersion.
This effect is frequency-dependent, thus,
utilizing dual-frequency signals makes it
TIME SYNCHRONIZATION possible to calculate and correct ionospheric
GNSS relies on the time it takes for delays.
signals to travel from multiple satellites to the Water vapor, clouds, and weather in the
receiver to calculate their position. All GNSS troposphere cause frequency-independent delay
satellites must be synchronized to a common in the signal. Tropospheric models in receivers
time standard to ensure they broadcast signals use parameters like temperature, pressure, and
with accurately known timestamps. Even a small humidity to estimate and correct these delays.
deviation in the satellite clocks or receiver’s
internal clock can cause substantial location Additional augmentation systems can
errors. correct for factors such as atmospheric
SOLUTION: interference, satellite orbit errors, and clock
– Atomic clocks in satellites to provide highly inaccuracies, enhancing the overall performance
accurate and stable timing of GNSS.
TYPES OF AUGMENTATION SYSTEMS: SIGNAL STRUCTURES AND
FREQUENCY MANAGEMENT
Satellite-Based Augmentation Systems
(SBAS) Code Division Multiple Access (CDMA)
– use additional satellites to broadcast correction – each satellite's signal is encoded with a
data unique code
– allows multiple signals to occupy the same
 WAAS (Wide Area Augmentation frequency band simultaneously
System) in the U.S.
– efficient and robust against interference in
 SDCM (System of Differential urban environments
Correction and Monitoring) in Russia
 EGNOS (European Geostationary Frequency Division Multiple Access (FDMA)
Navigation Overlay Service) in Europe – assigns a unique frequency band to each
 GAGAN (GPS Aided GEO Augmented satellite for its transmission
Navigation) in India – preventing overlap and ensuring clear
communication
– simpler but can be less efficient in frequency
Kalman filter use

– A mathematical algorithm that corrects errors

by making prediction based on its previous  GPS, Galileo, NavIC, and QZSS use
positions and velocities. It then compares this CDMA.
prediction to a new measurement (like a GPS  GLONASS initially used FDMA but also
reading) and checks for any differences. It trusts transitioned to CDMA.
the measurement to some degree but doesn’t rely  BeiDou system adopts a hybrid approach
on it completely due to noise. by using CDMA for its global services and
FMDA for its regional services.

REFERENCE SYSTEMS:
VELOCITY ESTIMATION
Space-Fixed Reference System – inertial
reference system to describe satellite motion Doppler Effect – If the satellite and receiver
move closer together, the signal frequency
Earth-Fixed Reference System or Geodetic increases; if they move apart, it decreases. This
Framework – refers to the system of shift, known as the Doppler shift, allows the
coordinates, reference points, and models used receiver to calculate its speed and direction of
to define the Earth’s shape, size, and movement.
gravitational field and used to describe the
locations of observation

 WGS (84World Geodetic System 1984)

 GTRF (Galileo Terrestrial Reference
Frame)
 PZ-90 (Parametric Leveling System 1990)
 IRS (Indian Reference System)
 CGCS2000 (Chinese Geodetic Coordinate
System 2000)
 JGD2000 (Japanese Geodetic Datum 2000)
APPLICATION BEIDOU
 Short Messaging Service (SMS)
GPS
– A unique feature of BeiDou is its satellite-
 Aviation based messaging capability, allowing users
– provide lateral and vertical guidance to send short messages even without
during landings in low-visibility cellular networks, particularly useful in
conditions, such as fog or heavy rain remote or disaster-prone areas.
 Vehicle and Smartphone Navigation  Logistics and Fleet Management
– provides turn-by-turn directions for – plays a crucial role in tracking vehicles
vehicles and pedestrians through real-time and cargo across China and internationally,
tracking helping logistics companies ensure timely
 Precision Agriculture deliveries
– guides automated tractors and drones to  Fisheries and Maritime Navigation
apply fertilizers or pesticides only where – BeiDou offers unique regional
needed enhancements and global coverage tailored
– generate field maps which helps monitor for specific applications in maritime
soil conditions, crop health, and yields navigation.
over time
NavIC
GLONASS
 Vehicle and Smartphone Navigation
 Military and Government Applications – Provide guidance to vehicles or pedestrian
– provides reliable positioning for Russian with mobile mapping and location-based
defense operations, ensuring precision in services to optimize routes and preventing
military activities, including navigation, collisions in congested areas
targeting, and logistics.  Disaster Management and Emergency
 Remote Sensing and Arctic Navigation Response
– Research stations and vessels navigating – supports search and rescue operations,
the Arctic waters rely on GLONASS for resource allocation, and relief distribution
accurate positioning and navigation by offering reliable geolocation data under
challenging conditions.
GALILEO  Precision Agriculture
 Aviation and Maritime Navigation – supports precision agriculture by
– enhances precise positioning services delivering accurate positional data that
crucial for aviation and maritime helps optimize crop management and
operations resource allocation.
 Autonomous Vehicles and Drones  Timing Synchronization in
– provides high-precision positioning Telecommunications
services that are crucial for the safe – offers timing data with nanosecond-level
navigation of autonomous vehicles accuracy, which telecommunications
towers and systems use to align their
 Scientific Research and Earth
transmissions
Observation
– high-resolution positioning enables  Military and Defense Applications
researchers to analyze tectonic activity – for missile guidance and unmanned
vehicle navigation
 QZSS (Quasi-Zenith Satellite System) Future trends

 Navigation and Transportation  Multi-GNSS Receivers

– QZSS significantly improves navigation – enhancing positioning accuracy through
accuracy, particularly in urban areas redundancy
– Smart city applications, such as urban  Quantum Clocks
traffic management systems and public – improve satellite timing precision,
transportation tracking reducing synchronization errors
 Disaster Management  Integration With 5g Networks and The
– help coordinate emergency response Internet of Things (IoT)
efforts by offering real-time data on the – providing ultra-reliable positioning for
location of responders and resources autonomous vehicles, smart cities, and
 Agriculture drone operations
– By employing QZSS, farmers can utilize  Network-Assisted GNSS (A-GNSS)
GPS-guided equipment for tasks such as – enhance satellite lock time and
planting, fertilizing, and harvesting. performance in urban environments
 Public Safety and Security  Low Earth Orbit (LEO) satellites
– police and emergency services can use – LEO satellites can offer faster signal
QZSS data to ensure rapid deployment of transmissions and better coverage in urban
resources during critical incidents. areas and indoors
 Space-Based Operations Beyond Earth’s
Orbit
CHALLENGES – Future satellites will provide navigation
and positioning for lunar missions, space
 Signal Vulnerability stations, and deep-space exploration
– anti-jamming technology are under  Enhanced Signal Structures Such as The
development, but no solution is yet foolproof Binary Offset Carrier (BOC)
 Cybersecurity Threats – improving resistance to interference and
– control centers and data transmission multipath errors
protocols is vulnerable to hacking
 Atmospheric Disturbances
– variability in atmospheric conditions still
STANDARDS AND GUIDELINES
introduces errors
 Inter-System Interference 1. Institute of Electrical and Electronics
– arises as GNSS constellations increasingly Engineers (IEEE)
share overlapping frequency – world’s largest technical professional
 Satellite Aging and Replacement organization
– Any delays in satellite launches, caused by – ensure that devices and networks operate
funding limitations, technical issues, or efficiently, remain interoperable, and provide
geopolitical conflicts, can degrade the consistent performance.
performance of the system.
○ IEEE 1588, known as the Precision Time
 Geopolitical Factors Protocol (PTP), is pivotal for achieving
– competition fosters innovation but risks nanosecond-level synchronization among
fragmentation in global navigation networked systems, such as maritime GNSS
receivers and satellite signals.
○ IEEE 1471 standard, which provides a 5. Federal Aviation Administration (FAA)
structured approach to the architectural and International Civil Aviation
description of software-intensive systems, Organization (ICAO)
ensures that all subsystems involved in ● ICAO's Performance-Based Navigation
navigation—including satellites, receivers, and (PBN)
ground control—can operate efficiently and ○ guidelines provide a framework for
cohesively. optimizing flight paths,
approaches, and landing
○ IEEE 1516 (High-Level Architecture - HLA) procedures
enables different navigation-related simulations, ○ By adhering the standards, pilots can
such as those modeling BeiDou's performance navigate with increased confidence,
alongside other GNSS systems, to function significantly minimizing the risk of
collaboratively, allowing for comprehensive accidents and ensuring safer skies.
analysis of system performance and
interoperability 6. U.S. Department of Defense (DoD) and
Military Standards (MIL-STD)
○ IEEE 1588, utilized in a fishing vessel for ● The DoD's IS-GPS-200 and IS-GPS-800
precise time synchronization with the satellite specifications are integral frameworks that
network, ensuring that its location data is outline how both military and civilian users
accurate and reliable, thereby enhancing the can access GPS signals, ensuring that users
crew's ability to navigate safely in deep-sea benefit from reliable and precise navigation
conditions. data.
● essential not only for everyday navigation but
also for national security and military
2. International Organization for operations, where accuracy can be a matter of
Standardization (ISO) life and death
– ISO 19116, which focuses on positioning ● MIL-STD protocols, guarantee secure and
services, and dependable communication, even in
– ISO 19814, which addresses satellite- contested environments where signals may
based augmentation be vulnerable to interference or jamming.

3. International Telecommunication Union 7. Radio Technical Commission for

(ITU) Maritime Services (RTCM)
– ensure interference-free communication ● RTCM ensures that widely-used systems like
between Global Navigation Satellite Systems GPS and BeiDou can achieve centimeter-
(GNSS) and other wireless technologies. level accuracy, which is crucial for vessels
operating in challenging environments such
○ ITU-R M.1902 outline specific frequency as narrow shipping lanes and crowded
allocations for GNSS signals, including bands harbors.
such as L1, L2, and L5 ● mitigating the risks associated with shallow
waters and avoiding potential collisions.

4. European Telecommunications Standards

Institute (ETSI)
– instrumental in ensuring that GNSS 8. International Maritime Organization
receivers and mobile devices, such as (IMO)
smartphones, accurately interpret location ● IMO governs maritime operations, setting
data. benchmarks that all vessels must adhere to
operate securely on the high seas.
● Safety of Life at Sea (SOLAS) convention,
requires that ships over a certain size be
 equipped with an Automatic Identification
System (AIS), which provides real-time
location data to other ships and shore
stations. AIS helps prevent collisions by
allowing ships to monitor each other’s
position, course, and speed.
● promote a safer environment for all who
traverse the seas

9. National Institute of Standards and

Technology (NIST)
● ensuring the accuracy and reliability of
navigation and telecommunications systems
through its development of standards related
to timekeeping and synchronization
● NIST helps maintain synchronization across
various networks and devices
● The standard behind the highly accurate
atomic clock for a precise timekeeping

10. GB/T (Guobiao Standards)

● Set of national standards established by the
Standardization Administration of China
● specify technical requirements, testing
methods, and performance evaluations for
navigation systems and equipment, ensuring
quality and interoperability
● Establishes performance metrics and
protocols to help ensure that navigation
devices meet specific operational
requirements, facilitating effective
integration into various applications such as
transportation, agriculture, and emergency
services