GPS Security Solutions

GPS Security Solutions

Excerpt of “Designing Around the Threat to Timing in Modern Networks”

A GPS Security Solutions Primer

As technology and services advance, GPS security solutions must keep up the pace. Reliable network timing is more critical than ever. While legacy analog networks traditionally required frequency synchronization from a central source, properly functioning modern networks require increasingly precise references to single-clock sources. This is a modern demand for telecommunications, media, IT and utility networks. As is the case with all critical requirements, there exists the threat of disruption – both intentional and accidental. In the case of network timing, which is commonly derived from a Global Navigation Satellite System (GNSS) source like GPS, the intentional GPS threats to disruption most often comes in the form of jamming or spoofing. The ease with which jamming and spoofing can be applied to GNSS systems has created the need to ensure that a common clock source can survive multiple types of disruption, be they local or widespread, short in duration or prolonged. This paper will describe the current need for network timing and the reality of the GPS threats against it. It will also explore the proper methodologies and systems that should be employed in network design and operation to protect the timing source and guarantee consistent, quality services. With attacks rising, your network needs GPS security solutions.

What Makes Network Timing Critical?

Data transactions between network equipment and applications that are distributed around the world are growing in number quickly year after year. Meanwhile, expectations for performance by users and service providers continue to get more demanding. GPS security solutions are needed. Highspeed, low latency, high throughput networks are being deployed to enable the normal demand plus new services. IT networks are being designed with faster interfaces, faster processors, and faster storage to shave every possible microsecond off transactions.

Smart Grid technologies are revolutionizing how power is generated and distributed, saving energy, and improving the performance of utilities. 5G wireless technologies have been deployed to satisfy the rapid growth in the number of wireless devices, as well as the demand for high bit rate, low latency services. Edge networks are bringing formerly centralized functions closer to their consumers, further augmenting performance. All of this depends on geographically diverse network architectures to operate.

Synchronization of network time – down to the microsecond –is critical for network performance, stability and most importantly, security. This is not optional. Any drift from a commonly referenced time causes operations to
unravel.

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Precision Timing Protocol (PTP)

PTP is used to counteract this issue, with a standard reference source invariably derived from an RF signal transmitted by the different GNSS satellite networks in Earth’s orbit. This is often achieved simply with an antenna at each location or for each different application. It is seemingly always available, which has caused a dependency that is now being exploited. GPS signals originate in space, far away from any terrestrial consumer of the signal. They are very low power, and well documented so the specifications are known. The signal can be spoofed and replaced with a similar signal of a higher power, or, more easily, jammed with different signal of a higher power. While spoofing is an intentional attempt to disrupt service reliant on GNSS signaling, jamming can be intentional or accidental. In modern war zones, jamming or spoofing GNSS signals is a standard tactic, as it is an effective way to insert chaos into standard operations, as well as disrupt tracking capabilities of weapons systems.

Even in peaceful regions, GPS jammers are widely available for purchase. Commercial drivers use them to disrupt monitoring of their delivery vehicle location or speed. Individuals use them to protect themselves from stalkers
using tracking devices. Journalists and detectives may use them to avoid being tracked when meeting with confidential sources. Sometimes, car thieves will use them to avoid being caught. For just a few hundred US dollars, it is possible to purchase a handheld jammer that will disrupt an entire city block – including the critical networks that run through it. While network time may be an afterthought for many networks, protection from the harm that GPS disruption can cause is relatively inexpensive and should be a standard component of network architecture.

To fully appreciate the importance of designing timing resiliency for networks, it is important to understand the applications of PTP in several common modern networks. Wireline networks, 5G wireless networks, power utility networks, and high-performance edge data networks are critical to our lives and our national security and need to be protected.

LEO solved GPS threats

Syncworks offers GPS security solutions that incorporate Low Earth Orbits (LEO) satellites. Above is a map of Low, Medium, and Geostationary Earth orbits. Lower latency and higher data rates are benefits of LEO.

Utilities and GPS Security

Our critical energy infrastructure is being upgraded to meet evolving standards for efficiency, output, stability, security, and environmental impact. As it stands today, power generation and distribution systems are a mix of old and new. This mix makes network timing and synchronization more critical components of utilities’ infrastructure. With recent weapon attacks in North Carolina, GPS security solutions and backup plans are essential.

In power generation, PTP is used to synchronize the clocks of generators, turbines, and other equipment. It is essential to maintaining a stable and reliable power grid. For example, PTP is used to synchronize the clocks of two generators operating in parallel. This ensures that the generators are consistently producing the same frequency and voltage. A lack of synchronization creates inconsistencies that can cause power brownouts and blackouts. PTP is also used to support frequency regulation of generators. This matches output to consumption, which is necessary to ensure an optimally efficient utility.

In power distribution, PTP is used to synchronize the clocks of substations, transformers, and other equipment. Consistency is necessary for not only efficiency, but also safety. For example, two substations connected by a transmission line could be receiving their timing source from separate GPS references. When things are working properly, they will be in phase with each other. But the loss of one reference at one substation with no backup source for PTP can cause widespread outages. This is a significant security concern, as any power outage results in
disruption of critical services and infrastructure. PTP is at the heart of future GPS security solutions.

Finally, it is more common than ever for businesses and residents to not only consume energy but produce it. The cost of solar, wind and other private power generation infrastructure has declined significantly in the past two decades. It is often the case that these systems produce more power than is consumed by the functions they support, especially during off peak times. Excess power is fed back into the utility power distribution network for use by other consumers. These private systems typically derive their timing from the larger distribution grid for this to work properly. Like wireless networks, power infrastructure is distributed, is largely outdoors, and can operated by multiple entities. IEEE 1588 indicates that power networks should not rely on GPS alone for network timing reference. The proper means of providing reliable network timing is by providing it from a central source with adequate protection and holdover.

GPS security solutions

The GPS antenna farm outside of Syncworks.

About Us Syncworks

Syncworks is a value-added stocking reseller of network sync and timing equipment for critical infrastructure companies. SyncCare and Field Services ensure your network equipment is flawlessly executed and supported.  

As a Microchip Diamond Partner, we maintain the largest and most diversified stocking supply of Microchip network sync & timing products to meet our customers’ every need when it comes to sync and timing technology.  

For more information, contact sales@syncworks.com or call (904) 280-1234

GPS/GNSS White Papers

GPS/GNSS White Papers

Curated Collection of Microchip GPS/GNSS White Papers & Reports


GNSS (Global Navigation Satellite System) technology includes GPS (Global Positioning System, United States owned and operated) along with Global Satellite Navigation Systems operated by China (Beidu) and Russia (Glonass). Beyond providing location and positioning information, GNSS is used to deliver accurate timing that is distributed in communications networks for a variety of applications. An interruption or degradation of these timing signals can impact mission critical applications and services.

 

Background White Paper GNSS/GPS Information 

In the intricate realm of Global Navigation Satellite Systems (GNSS) and their ubiquitous counterpart, the Global Positioning System (GPS), the importance of white papers stands as a beacon guiding engineers through the complexities. These white papers are not mere documents; they are gateways to understanding the engineering intricacies that underpin modern navigation technologies. This post delves into the world of GNSS/GPS white papers, unraveling the engineering marvels that shape our global positioning landscape.

The Foundation of GNSS/GPS White Papers

At their core, GNSS/GPS white papers serve as authoritative documents, encapsulating a wealth of knowledge, research findings, and engineering insights. These papers emanate from the collaborative efforts of engineers, researchers, and experts who navigate the intricate landscape of satellite-based navigation systems. The foundation of these papers lies in the need to disseminate cutting-edge engineering knowledge, making them indispensable resources for professionals in the field.

Understanding GNSS/GPS Fundamentals

A well-crafted GNSS/GPS white paper is an invaluable resource for engineers seeking a profound understanding of the fundamentals. It dives deep into the intricacies of satellite orbits, signal processing, and the synchronization mechanisms that orchestrate the harmonious dance of satellites in the Earth’s exosphere. Engineers exploring these papers embark on a journey through the technological intricacies that empower our smartphones, navigation devices, and countless other applications.

Signal Processing: The Heartbeat of GNSS

One of the engineering-centric aspects explored in GNSS/GPS white papers is signal processing — the heartbeat of satellite navigation. Engineers dissect the algorithms and methodologies employed to extract accurate position, velocity, and timing information from the signals transmitted by satellites. Understanding signal processing intricacies is crucial for enhancing the accuracy and reliability of GNSS systems, especially in challenging environments where signal integrity faces potential disruptions.

Overcoming Challenges: Multipath, Interference, and Accuracy

White papers in the GNSS/GPS domain unravel the challenges faced by engineers in achieving pinpoint accuracy. Multipath interference, a phenomenon where signals reflect off surfaces before reaching the receiver, poses a significant hurdle. These papers explore innovative techniques and advanced algorithms engineered to mitigate multipath effects and enhance overall system accuracy. Additionally, they delve into strategies to counteract interference from various sources, ensuring robust and uninterrupted navigation.

Innovation and Evolving Technologies

The engineering landscape is dynamic, and GNSS/GPS white papers serve as compasses guiding engineers through the ever-evolving terrain of innovation. They shed light on emerging technologies such as Real-Time Kinematic (RTK) positioning, Precise Point Positioning (PPP), and integration with other sensor technologies. Engineers immerse themselves in these papers to stay abreast of advancements that shape the future of satellite-based navigation.

Security in the Satellite Constellation

The security of GNSS/GPS systems is a paramount concern, and white papers play a pivotal role in addressing this aspect. Engineers explore cryptographic techniques, anti-jamming measures, and resilient architectures designed to safeguard satellite constellations from malicious attacks. The engineering insights provided in these papers contribute to the ongoing efforts to fortify GNSS/GPS systems against potential threats.

Real-World Applications and Case Studies

GNSS/GPS white papers bridge the gap between theory and real-world applications. Engineers are exposed to case studies detailing the implementation of satellite navigation in diverse fields — from autonomous vehicles and precision agriculture to disaster response and infrastructure development. These case studies offer invaluable engineering lessons drawn from practical experiences, enriching the knowledge base of professionals.

In conclusion, GNSS/GPS white papers are compasses guiding engineers through the intricate engineering landscapes of satellite navigation. They unravel the complexities of signal processing, address challenges, explore innovations, enhance security, and bridge the gap between theory and application. Engineers who delve into these white papers embark on a journey of continuous learning, contributing to the evolution of GNSS/GPS technologies that shape our connected world. As we navigate the future, the insights gleaned from these engineering-centric documents will continue to steer the course of innovation and excellence in satellite-based navigation systems.

Expert GPS Antenna Installation for Network Sync and Timing

Expert GPS Antenna Installation for Network Sync and Timing

PTP, NTP, and BIT Synchronization and Timing Need Resilient GPS

GPS Antenna Installation for Network Sync and Timing

Our turnkey solution for every GPS antenna installation process is designed to simplify the process of implementing and maintaining GPS antennas within your network. Here’s what you can expect when you choose expert GPS Antenna Installation for Network Sync and Timing:

1. Reliable GPS Antennas
We provide GPS antennas known for their reliability and precision. Our antennas are designed to withstand the harshest environmental conditions while delivering consistent, high-quality signal reception.

2. Customized Solutions
We understand that every network is unique. Our team of experienced engineers will work closely with you to tailor a GPS antenna installation solution that meets your specific requirements, whether it’s for a telecom, cable, or utility network.

3. Expert Installation
One of the key differentiators of our turnkey solution is the inclusion of experienced technicians who specialize in GPS antenna installation. Our technicians are not only skilled in deploying the latest antenna technology but are also well-versed in industry best practices.

4. Maintenance and Support
Your network’s precision is an ongoing concern. We offer comprehensive maintenance packages to ensure that your GPS antennas continue to perform optimally over time. Our support team is available around the clock to address any issues or concerns promptly.

5. Seamless Integration
Syncworks understands that integrating new technology into an existing network can be challenging. Our team will work closely with your engineers to ensure a smooth and seamless integration process, minimizing disruptions and downtime. We can also retrofit your current antenna configuration, if possible, to reduce costs while ensuring reliability.

6. Cost-Efficiency
We aim to provide a cost-effective solution that maximizes your return on investment. By preventing timing errors and network disruptions, our GPS antenna solution can ultimately save you time and money.

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Elevate Your GPS Antenna Installation for Network Sync and Timing

Technician finishing a GPS antenna install.

Our field services crews are dispatched nationwide for emergency support or scheduled maintainance.

A Failed GPS Signal. What’s The Worst That Can Happen?

When GPS signals are lost, the repercussions can extend far beyond a momentary inconvenience. In fact, a network failure may occur, triggering a mandatory report to the Federal Communications Commission (FCC). This underscores the critical need for expert GPS installation services to ensure uninterrupted connectivity and reliable navigation.

In the United States, the FCC mandates that telecommunication providers adhere to strict standards regarding the reliability and availability of their services. When network failures occur due to GPS signal issues, providers are obligated to report such incidents to the FCC. This not only triggers investigations but can also result in penalties if the failures are found to be due to inadequate GPS infrastructure.

 

Enhance Your Network’s Precision Today

In an industry where timing is everything, trust Syncworks to provide the turnkey GPS antenna solution you need. Our commitment to quality, precision, and reliability is unmatched, and our experienced technicians are ready to transform your network into a well-synchronized powerhouse.

Don’t compromise on precision when it comes to your network’s timing. Contact us today to learn more about how our turnkey GPS antenna solution can benefit your telecom, cable, or utility network. Elevate your network to new heights of precision with Syncworks.

Cost-saving retrofit GPS install.

GPS antenna installation

About Syncworks

Syncworks is a the national leader in GPS security. Critical infrastructure in the US is a top priority at the highest level of government. Our mission is to enable, educate, and support efforts to become complaint with celestial and terrestrial GPS systems working together.
  
Our flagship product, the TimeProvider® 4100, is a gateway clock that accepts multiple inputs from Global Navigation Satellite Systems (GNSS), Synchronous Ethernet (SynE), and IEEE 1588 PTP Grandmaster Clock and E1/T1 digital transmission links.  

As of January 1, 2024, we have expanded our Field Services to include Antenna Installation and Entrance Facility Cabling, Legacy Equipment Decom and Traffic Migration, Disposal (hazmat) Services, Radio Commissioning (MW, P-LTE, CBRS), Enterprise Wi-Fi.

For more information, contact sales@syncworks.com or call (904) 280-1234

GPS Spoofing Defined As A Cyber Attack

GPS Spoofing Defined As A Cyber Attack

GPS Spoofing On the Rise

GPS spoofing is a form of cyber attack that involves manipulating GPS signals to provide false location and time information. This type of attack can have serious consequences, particularly when it comes to network synchronization and timing. 

GPS signals are widely used in many industries, including telecommunications, financial services, and transportation. In these industries, accurate timing and synchronization are critical to ensure the smooth functioning of systems and services. 

GPS signals are used to synchronize network clocks, which in turn helps to ensure that data is transmitted accurately and efficiently. Without accurate timing, network traffic can become congested and data can be lost, resulting in errors and delays.

However, GPS spoofing can disrupt the accuracy of GPS signals, leading to incorrect time and location data. This can cause network synchronization to fail, leading to errors and delays in data transmission. 

For example, a cyber attacker could spoof GPS signals to provide false time information to a financial institution’s trading system. This could cause the system to execute trades at the wrong time, leading to losses for the institution and its clients. 

Similarly, in the transportation industry, GPS spoofing could cause problems with the timing of trains, planes, and automobiles. A GPS spoofing attack on a train system, for instance, could cause trains to arrive at the wrong time or to collide with each other. 

To prevent GPS spoofing attacks, industries that rely on GPS signals for timing and synchronization must take steps to secure their systems. This can include using encryption to protect GPS signals, deploying anti-spoofing technologies, and using multiple sources of timing information to ensure redundancy. 

In conclusion, GPS spoofing can have serious consequences for network synchronization and timing, with potential impacts on industries such as telecommunications, finance, and transportation. To mitigate the risk of GPS spoofing attacks, it is important for organizations to take steps to secure their systems and use multiple sources of timing information.

 

Screenshot 2024 02 15 133628

Denver Airport Spoofing Attack

Event Summary From the US Cybersecurity and Infrastructure Security Agency (CISA)

In January 2022, a GPS interference event occurred over a thirty-three (33) hour period in the vicinity of Denver International Airport due to a transmitter errantly broadcasting in the GPS frequency. Interference was
first detected by aircraft pilots and communicated to Federal Aviation Administration (FAA) Air Traffic Control Facilities. Due to the significant number of reports, the FAA issued a Notice to Air Missions warning of the GPS interference. Get the full CISA report.

Operators of systems from a wide range of critical infrastructure that rely on the GPS signal for uninterrupted PNT services also detected interference with (1) surface and rail traffic and (2) communications towers and
services using GPS timing signals. Ground-based industry users of GPS/PNT services and others reported GPS interference to the United States Coast Guard Navigation Center (NAVCEN) and the Federal Communications Commission (FCC) Public Safety and Homeland Security Bureau. Departments and agencies responsible for monitoring and coordinating response to GPS interference events
implemented the established national coordination process. The FCC Enforcement Bureau deployed, located, and coordinated shut down of the emitter. No accidents or injuries occurred because of the GPS interference incident. However, several critical infrastructure sectors were degraded. Many systems that detected the event had resilient alternate timing built in for backup or fail-over timing and experienced minor or no degradation of services.

An investigation of the interference positively identified an emitter unintentionally transmitting a signal within the GPS L1 frequency. Some receivers within a line of sight of the transmitter experienced GPS signal
disruption. The affected area on the ground covered approximately 50 nautical mile radius on the ground and spanned approximately 230 nautical miles in distance from the interfering transmitter at flight levels up to
approximately 36,000 feet.

About Syncworks

Syncworks is a value-added reseller of network sync and timing equipment for critical infrastructure companies. SyncCare and Field Services ensure your network equipment is flawlessly executed and supported. Our warehouse is stocked with new Microchip products, as well as Symmetricom, Datum, Telecom Solutions, and Microsemi brands.

Syncworks delivers the highest level of expertise to every project and offers a complete menu of network synchronization products and services. Our flagship product, the TimeProvider® 4100, is a gateway clock that accepts multiple inputs from Global Navigation Satellite Systems (GNSS), Synchronous Ethernet (SynE), and 1588 PTP Grandmaster Clock and E1/T1 digital transmission links.

As a Microchip Diamond Partner, we maintain the largest and most diversified stocking supply of Microchip network sync & timing products to meet our customers’ every need when it comes to sync and timing technology.

For more information, contact help@syncworks.com or call (904) 280-1234

 

GPS Antenna Glossary of Terms

GPS Antenna Glossary of Terms

GPS Antenna Terms and Definitions

GPS antennas are a lynchpin that holds together what comes from the sky and what shows up on the Earth. Let’s learn the names and meanings of their parts and processes. Source

Syncworks carries complete GPS antenna kits, including cables, connectors, and splitters. Our Field Services ensure that your GPS signal is secure and reliable. With engineering and completion reports included, you’ll appreciate our high standards now and in the future. 

Cost is always a consideration. We have cost-saving measures that our Field Services can deliver. Check out one way here. 

GPS antenna kits in a box
white conical GPS satellite receiver
50 74000 4 Splitter
   
ASCII A 7-bit wide serial code describing numbers, upper and lower case characters, special and non-printing characters. Typically used for textual data.
Acquisition The process of locking onto a satellite’s C/A code and P code. A receiver acquires all available satellites when it is first powered up, then acquires additional satellites as they become available and continues tracking them until they become unavailable.
Anti-Spoofing Denial of the P-code by the Control Segment is called Anti-Spoofing. It is normally replaced by encrypted Y-code, [see P-Code and Y-Code]
Attenuation Reduction of signal strength
Azimuth The horizontal direction of a celestial point from a terrestrial point, expressed as the angular distance from 000° (reference) clockwise through 360°. The reference point is generally True North, but may be Magnetic North, or Relative (ship’s head).
Bearing The horizontal direction of one terrestrial point from another terrestrial point, expressed as the angular distance from a reference direction, usually measured from 000° at the reference direction clockwise through 360°. The reference point may be True North, Magnetic North, or Relative (ship’s head).
Carrier The steady transmitted RF signal whose amplitude, frequency, or phase may be modulated to carry information.
Carrier Phase Ambiguity The number of integer carrier phase cycles between the user and the satellite at the start of tracking. (Sometimes ambiguity for short)
Carrier Phase Measurements These are “accumulated doppler range” (ADR) measurements. They contain
Measurements the instantaneous phase of the signal (modulo 1 cycle) plus some arbitrary number of integer cycles. Once the receiver is tracking the satellite, the integer number of cycles correctly accumulates the change in range seen by the receiver. When a “lock break” occurs, this accumulated value can jump an arbitrary integer number of cycles (this is called a cycle slip).
Checksum By NMEA standard, a validity check performed on the data contained in the sentences, calculated by the talker, appended to the message, then recalculated by the listener for comparison to determine if the message was received correctly. Required for some sentences, optional for all others.
Circular Error Probable (CEP) Circular error probable; the radius of a circle such that 50% of a set of events occur inside the boundary.
Coarse Acquisition (C/A) Code A pseudorandom string of bits that is used primarily by commercial GPS receivers to determine the range to the transmitting GPS satellite. The 1023 chip C/A code repeats every 1 ms giving a code chip length of 300 m which, is very easy to lock onto.
Communication Protocol A method established for message transfer between a talker and a listener which includes the message format and the sequence in which the messages are to be transferred. Also includes the signalling requirements such as bit rate, stop bits, parity, and bits per character.
Control Segment The Master Control Station and the globally dispersed Reference Stations used to manage the GPS satellites, determine their precise orbital parameters, and synchronize their clocks.
Coordinated Universal Time (UTC) This time system uses the second-defined true angular rotation of the Earth measured as if the Earth rotated about its Conventional Terrestrial Pole. However, UTC is adjusted only in increments of one second. The time zone of UTC is that of Greenwich Mean Time (GMT).
Course The horizontal direction in which a vessel is to be steered or is being steered; the direction of travel through the air or water. Expressed as angular distance from reference North (either true, magnetic, compass, or grid), usually 000° (north), clockwise through 360°. Strictly, the term applies to direction through the air or water, not the direction intended to be made good over the ground. Differs from heading.
Course Made Good (CMG) The single resultant direction from a given point of departure to a subsequent position; the direction of the net movement from one point to the other. This often varies from the track caused by inaccuracies in steering, currents, cross-winds, etc. This term is often considered to be synonymous with Track Made Good, however, Course Made Good is the more correct term.
Course Over Ground (COG) The actual path of a vessel with respect to the Earth (a misnomer in that courses are directions steered or intended to be steered through the water with respect to a reference meridian); this will not be a straight line if the vessel’s heading yaws back and forth across the course.
Cross Track Error (XTE) The distance from the vessel’s present position to the closest point on a great Circle line connecting the current waypoint coordinates. If a track offset has been specified in the GPSCard SETNAV command, the cross track error will be relative to the offset track great circle line.
Cycle Slip When the carrier phase measurement jumps by an arbitrary number of integer cycles. It is generally caused by a break in the signal tracking due to shading or some similar occurrence.
Dead Reckoning (DR) The process of determining a vessel’s approximate position by applying from its last known position a vector or a series of consecutive vectors representing the run that has since been made, using only the courses being steered, and the distance run as determined by log, receiver rpm, or calculations from speed measurements.
Destination The immediate geographic point of interest to which a vessel is navigating. It may be the next waypoint along a route of waypoints or the final destination of a voyage.
Differential GPS (DGPS) A technique to improve GPS accuracy that uses pseudorange errors at a known location to improve the measurements made by other GPS receivers within the same general geographic area.
Dilution of Precision (DOP) A numerical value expressing the confidence factor of the position solution based on current satellite geometry. The lower the value, the greater the confidence in the solution. DOP can be expressed in the following forms.
  GDOP -uncertainty of all parameters (latitude, longitude, height, clock offset)
  PDOP -uncertainty of 3D parameters (latitude, longitude, height)
  HTDOP -uncertainty of 2D and time parameters (latitude, longitude, time)
  HDOP -uncertainty of 2D parameters (latitude, longitude)
  VDOP -uncertainty of height parameter
  TDOP -uncertainty of clock offset parameter
Doppler The change in frequency of sound, light or other wave caused by movement of its source relative to the observer.
Doppler Aiding A signal processing strategy, which uses a measured Doppler shift to help a receiver smoothly track the GPS signal, to allow more precise velocity and position measurement.
Double-Difference A mathematical technique comparing observations by differencing between receiver channels and then between the reference and rover receivers.
Double-Difference Carrier Phase Ambiguity Carrier phase ambiguities which are differenced between receiver channels and between the reference and rover receivers. They are estimated when a double-difference mechanism is used for carrier phase positioning. (Sometimes double-difference ambiguity or ambiguity, for short)
Earth-Centred-Earth-Fixed (ECEF) This is a coordinate-ordinate system which has the X-coordinate in the earth’s equatorial plane pointing to the Greenwich prime meridian, the Z-axis pointing to the north pole, and the Y-axis in the equatorial plane 90° from the X-axis with an orientation which forms a right-handed XYZ system.
Elevation The angle from the horizon to the observed position of a satellite.
Ellipsoid A smooth mathematical surface which represents the earth’s shape and very closely approximates the geoid. It is used as a reference surface for geodetic surveys, refer to the MATCHEDPOS log in user manual Volume 2, Command and Log Reference.
Ellipsoidal Height Height above a defined ellipsoid approximating the surface of the earth.
Ephemeris A set of satellite orbit parameters that are used by a GPS receiver to calculate precise GPS satellite positions and velocities. The ephemeris is used in the determination of the navigation solution and is updated periodically by the satellite to maintain the accuracy of GPS receivers.
Ephemeris Data The data downlinked by a GPS satellite describing its own orbital position with respect to time.
Epoch Strictly a specific point in time. Typically when an observation is made.
Field A character or string of characters immediately preceded by a field delimiter.
Fixed Ambiguity Estimates Carrier phase ambiguity estimates which are set to a given number and held constant. Usually they are set to integers or values derived from linear combinations of integers.
Fixed Discrete Ambiguity Estimates Carrier phase ambiguities which are set to values which are members of a predetermined set of discrete possibilities, and then held constant.
Fixed Field A field in which the number of characters is fixed. For data fields, such fields are shown in the sentence definitions with no decimal point. Other fields which fall into this category are the address field and the checksum field (if present).
Fixed Integer Ambiguity Estimates Carrier phase ambiguities which are set to integer values and then held constant.
Flash ROM Programmable read-only memory.
Floating Ambiguity Estimates Ambiguity estimates which are not held to a constant value, but are allowed to gradually converge to the correct solution.
GAGAN GPS aided Geo Augmented Navigation
Geometric Dilution of Precision (GDOP) [See DOP]
Geoid The shape of the earth if it were considered as a sea level surface extended continuously through the continents. The geoid is an equipotential surface coincident with mean sea level to which at every point the plumb line (direction in which gravity acts) is perpendicular. The geoid, affected by local gravity disturbances, has an irregular shape.
Geodetic Datum The reference ellipsoid surface that defines the coordinate system.
Geostationary A satellite orbit along the equator that results in a constant fixed position over a particular reference point on the earth’s surface. (GPS satellites are not geostationary.)
Global Positioning System (GPS) Full name is NAVSTAR Global Positioning System. A space-based radio Positioning system which provides suitably equipped users with accurate position, velocity and time data. GPS provides this data free of direct user charge worldwide, continuously, and under all weather conditions. The GPS constellation consists of 24 orbiting satellites, four equally spaced around each of six different orbital planes. The system is being developed by the Department of Defence under U.S. Air Force management.
Great Circle The shortest distance between any two points along the surface of a sphere or ellipsoid, and therefore the shortest navigation distance between any two points on the Earth. Also called Geodesic Line.
Handshaking Predetermined hardware or software activity designed to establish or maintain two machines or programs in synchronization. Handshaking concerns the exchange of messages or packets of data between two systems with limited buffers. Hardware handshaking uses voltage levels or pulses in wires to carry the handshaking signals. Software handshaking uses data units (e.g. ASCII characters) carried by some underlying communication medium.
Horizontal Dilution of Precision (HDOP) [See DOP]
Horizontal and Time Dilution of Precision (HTDOP) [See DOP]
Heading The direction in which a vessel points or heads at any instant, expressed in degrees 000° clockwise through 360° and may be referenced to True North, Magnetic North, or Grid North. The heading of a vessel is also called the ship’s head. Heading is a constantly changing value as the vessel oscillates or yaws across the course due to the effects of the air or sea, cross currents, and steering errors.
Integer Ambiguity Estimates Carrier phase ambiguity estimates which are only allowed to take on integer values.
Iono-Free Carrier Phase Observation A linear combination of L1 and L2 carrier phase measurements which provides an estimate of the carrier phase observation on one frequency with the effects of the ionosphere removed. It provides a different ambiguity value (non-integer) than a simple measurement on that frequency.
Kinematic The user’s GPS antenna is moving. In GPS, this term is typically used with precise carrier phase positioning, and the term dynamic is used with pseudorange positioning.
L1 Frequency The 1575.42 MHz GPS carrier frequency which contains the course acquisition (C/A) code, as well as encrypted P-code, and navigation messages used by commercial GPS receivers.
L2 Frequency The 1227.60 MHz. secondary GPS carrier frequency, containing only encrypted P-code, used primarily to calculate signal delays caused by the ionosphere.
Lane A particular discrete ambiguity value on one carrier phase range measurement or double difference carrier phase observation. The type of measurement is not specified (L1, L2, L1-L2, iono-free)
L-Band The range of radio frequencies that includes the GPS carrier frequencies L1 and L2 and the TerraStar satellite broadcast signal.
Local Observation Set An observation set, as described below, taken by the receiver on which the software is operating as opposed to an observation taken at another receiver (the reference station) and transmitted through a radio link.
Local Tangent Plane A coordinate system based on a plane tangent to the ellipsoid’s surface at the user’s location. The three coordinates are east, north and up. Latitude, longitude and height positions operate in this coordinate system.
Low-latency Solution A position solution which is based on a prediction. A model (based on previous reference station observations) is used to estimate what the observations will be at a given time epoch. These estimated reference station observations are combined with actual measurements taken at the remote station to provide a position solution.
Magnetic Bearing Bearing relative to magnetic north; compass bearing corrected for deviation.
Magnetic Heading Heading relative to magnetic north.
Magnetic Variation The angle between the magnetic and geographic meridians at any place, expressed in degrees and minutes east or west to indicate the direction of magnetic north from true north.
Mask Angle The minimum GPS satellite elevation angle permitted by a particular receiver design. Satellites below this angle will not be used in position solution.
Matched Observation Set Pair Observations from both the reference station and the local receiver which have been matched by time epoch, contain the same satellites, and are corrected for any known offsets.
Measurement Error Variance The square of the standard deviation of a measurement quantity. The standard deviation is representative of the error typically expected in a measured value of that quantity.
Measurement Time Epoch The point in time at which a GPSCard takes a measurement.
Multipath Errors GPS positioning errors caused by the interaction of the GPS satellite signal and its reflections.
Non-Volatile Memory A type of memory device that retains data in the absence of a power supply.
Null Field By NMEA standard, indicates that data is not available for the field. Indicated by two ASCII commas, i.e., “,,” (HEX 2C2C), or, for the last data field in a sentence, one comma followed by either the checksum delimiter “*” (HEX 2A) or the sentence delimiters <CR><LF> (HEX 0D0A). [Note: the ASCII Null character (HEX 00) is not to be used for null fields.]
Obscuration Term used to describe periods of time when a GPS receiver’s line-of-sight to GPS satellites is blocked by natural or man-made objects.
Observation Any measurement. The two observations used in NovAtel’s RTK algorithms are the pseudorange measurement and the carrier phase measurement.
Observation Set A set of GPSCard measurements taken at a given time which includes one time for all measurements, and the following for each satellite tracked: PRN number, pseudorange or carrier phase or both, lock time count, signal strength, and tracking status. Either L1 only or L1 and L2 measurements are included in the set. The observation set is assumed to contain information indicating how many satellites it contains and which ones have L1-only and which ones have L1/L2 pairs.
Origin Waypoint The starting point of the present navigation leg, expressed in latitude and longitude.
Parallel Receiver A receiver that monitors four or more satellites simultaneously with independent channels.
Parity The even or odd quality of the number of ones or zeroes in a binary code. Parity is often used to determine the integrity of data especially after transmission.
Perigee The point in a body’s orbit at which it is nearest the earth.
P-Code Precise code or protected code. A pseudorandom string of bits that is used by GPS receivers to determine the range to the transmitting GPS satellite. P-code is replaced by an encrypted Y-code when Anti-Spoofing is active. Y-code is intended to be available only to authorized (primarily military) users. [See Anti-SpoofingC/A Code and Y-Code]
PDOP Position Dilution of Precision [See DOP]
Precise Positioning Service (PPS) The GPS positioning, velocity, and time service which is available on a continuous, worldwide basis to users authorized by the U.S. Department of Defence (typically using P-Code).
PRN Number A number assigned by the GPS system designers to a given set of pseudorandom codes. Typically, a particular satellite will keep its PRN (and hence its code assignment) indefinitely, or at least for a long period of time. It is commonly used as a way to label a particular satellite.
Pseudolite An Earth-based transmitter designed to mimic a satellite. May be used to transmit differential corrections.
Pseudorange The calculated range from the GPS receiver to the satellite determined by taking the difference between the measured satellite transmit time and the receiver time of measurement, and multiplying by the speed of light. Contains several sources of error.
Pseudorange Measurements Measurements made using one of the pseudorandom codes on the GPS signals. They provide an unambiguous measure of the range to the satellite including the effect of the satellite and user clock biases.
Receiver Channels A GPS receiver specification which indicates the number of independent hardware signal processing channels included in the receiver design.
Reference Satellite n a double difference implementation, measurements are differenced between different satellites on one receiver in order to cancel the correlated errors. Usually one satellite is chosen as the “reference, and all others are differenced with it.
Reference Station The GPS receiver which is acting as the stationary reference. It has a known position and transmits messages for the rover receiver to use to calculate its position.
Relative Bearing Bearing relative to heading or to the vessel.
Remote/ Rover Receiver The GPS receiver which does not know its position and needs to receive measurements from a reference station to calculate differential GPS positions. (The terms remote and rover are interchangeable.)
Residual In the context of measurement, the residual is the misclosure between the calculated measurements, using the position solution and actual measurements.
Root Mean Square (RMS) A probability level of 68%.
Route A planned course of travel, usually composed of more than one navigation leg.
RT-20 NovAtel’s Double Differencing Technology for real-time kinematic (RTK) carrier phase floating ambiguity resolution.
Radio Technical Commission for Aeronautics (RTCA) An organization which developed and defined a message format for differential positioning.
Radio Technical Commission for Maritime Services (RTCM) An organization which developed and defined the SC-104 message format for differential positioning.
Real-Time Kinematic (RTK) A type of differential positioning based on observations of carrier phase. In this document it is also used with reference to RT-2™ and RT-20.
Satellite-Based Augmentation System (SBAS) A type of geo-stationary satellite system that improves the accuracy, integrity, and availability of the basic GPS signals. This includes WAAS, EGNOS, and MSAS.
Selected Waypoint he waypoint currently selected to be the point toward which the vessel is travelling. Also called “to waypoint, destination or destination waypoint.
Selective Availability (SA) The method used by the United States Department of Defence to control access to the full accuracy achievable by civilian GPS equipment (generally by introducing timing and ephemeris errors).
Sequential Receiver A GPS receiver in which the number of satellite signals to be tracked exceeds the number of available hardware channels. Sequential receivers periodically reassign hardware channels to particular satellite signals in a predetermined sequence.
Spherical Error Probable (SEP) The radius of a sphere, centred at the user’s true location, that contains 50 percent of the individual three-dimensional position measurements made using a particular navigation system.
Spheroid Sometimes known as ellipsoid; a perfect mathematical figure which very closely approximates the geoid. Used as a surface of reference for geodetic surveys.
Standard Positioning Service (SPS) A positioning service made available by the United States Department of Defence which is available to all GPS civilian users on a continuous, worldwide basis (typically using C/A Code).
Space Vehicle ID (SV) Sometimes used as SVID. A unique number assigned to each satellite for identification purposes. The ‘space vehicle’ is a GPS satellite.
TDOP Time Dilution of Precision [See DOP]
Three-Dimensional Coverage The number of hours-per-day when four or more satellites are available with acceptable positioning geometry. Four visible satellites are required to determine location and altitude.
Three-Dimensional (3D) Navigation Navigation mode in which altitude and horizontal position are determined from satellite range measurements.
Time-To-First-Fix (TTFF) The actual time required by a GPS receiver to achieve a position solution. This specification will vary with the operating state of the receiver, the length of time since the last position fix, the location of the last fix, and the specific receiver design.
Track A planned or intended horizontal path of travel with respect to the Earth rather than the air or water. The track is expressed in degrees from 000° clockwise through 360° (true, magnetic, or grid).
Track Made Good The single resultant direction from a point of departure to a point of arrival or subsequent position at any given time; may be considered synonymous with Course Made Good.
True Bearing Bearing relative to true north; compass bearing corrected for compass error.
True Heading Heading relative to true north.
Two-Dimensional Coverage The number of hours-per-day with three or more satellites visible. Three visible satellites can be used to determine location if the GPS receiver is designed to accept an external altitude input.
Two-Dimensional (2D) Navigation Navigation mode in which a fixed value of altitude is used for one or more position calculations while horizontal (2D) position can vary freely based on satellite range measurements.
Undulation The distance of the geoid above (positive) or below (negative) the mathematical reference ellipsoid (spheroid). Also known as geoidal separation, geoidal undulation, geoidal height.
Update Rate The GPS receiver specification which indicates the solution rate provided by the receiver when operating normally.
UTC [See Coordinated Universal Time]
VDOP Vertical Dilution of Precision [See DOP]
Variable Field By NMEA standards, a data field which may or may not contain a decimal point and which may vary in precision following the decimal point depending on the requirements and the accuracy of the measuring device.
World Geodetic System 1984 (WGS84) An ellipsoid designed to fit the shape of the entire Earth as well as possible with a single ellipsoid. It is often used as a reference on a worldwide basis, while other ellipsoids are used locally to provide a better fit to the Earth in a local region. GPS uses the centre of the WGS-84 ellipsoid as the centre of the GPS ECEF reference frame.
Waypoint A reference point on a track.
Wide Lane A particular integer ambiguity value on one carrier phase range measurement or double difference carrier phase observation when the difference of the L1 and L2 measurements is used. It is a carrier phase observable formed by subtracting L2 from L1 carrier phase data: Φ’ = Φ1 – Φ2. The corresponding wavelength is 86.2 cm
Y-Code An encrypted form of P-Code. Satellites transmit Y-Code in replace of P-Code when Anti-Spoofing is in effect. [See P-Code and Anti-Spoofing]

About Syncworks

Syncworks is a the national leader in GPS security. Critical infrastructure in the US is a top priority at the highest level of government. Our mission is to enable, educate, and support efforts to become complaint with celestial and terrestrial GPS systems working together.
  
Our flagship product, the TimeProvider® 4100, is a gateway clock that accepts multiple inputs from Global Navigation Satellite Systems (GNSS), Synchronous Ethernet (SynE), and IEEE 1588 PTP Grandmaster Clock and E1/T1 digital transmission links.  

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