Telematics and GPS
Tracking Glossary
A working reference for the terms used every day in building trackers and platforms: the satellite systems, the protocols, the standards, the connectivity modes, and the device internals. Each entry is written for engineers and product people who need a precise, accurate definition rather than marketing copy.
HOW TO USE THIS
The Vocabulary of Telematics
Telematics sits at the intersection of satellite navigation, embedded hardware, cellular networking, and cloud software, and each of those fields brings its own dense vocabulary. A conversation about a tracker can move from GNSS constellations to CAN bus signals to MQTT topics to AIS 140 compliance in the space of a single sentence, and the terms are easy to confuse. This glossary is a shared reference for product teams, engineers, and partners so that everyone means the same thing by the same word.
Each definition is two to four sentences and aims for engineering accuracy rather than brevity for its own sake. Where a term maps directly to a buildable capability, the entry links to the relevant service so you can go from definition to capability in one click. The terms are grouped into three alphabetical blocks below.
TERMS A TO G
A to G
A-GPS / A-GNSS
Assisted GPS or GNSS, a technique where the receiver downloads satellite orbit and clock data (ephemeris and almanac) over the cellular network instead of decoding it slowly from the satellites themselves. This dramatically shortens the time to first fix, often from over 30 seconds cold to a few seconds. It is standard on cellular trackers because the modem already has a data link to fetch the assistance data.
AIS 140
An Indian standard from the Automotive Industry Standards body that defines the requirements for vehicle location tracking and emergency response devices in public and commercial transport. It mandates GNSS with NavIC support, a panic button wired to the ERSS 112 emergency system, specified backend interfaces, and over-the-air capability. Building a compliant device touches firmware, hardware, and certification, covered under AIS 140 and NavIC compliance engineering.
BCC (Backend Control Centre)
The server-side platform that AIS 140 devices report into, responsible for receiving location streams, storing them, and forwarding to government and regulatory backends where required. The standard specifies the message formats and interfaces a compliant BCC must support. In practice the BCC is the ingestion, storage, and integration layer of the telematics backend.
BeiDou
China's global navigation satellite system, fully operational worldwide since 2020. Like GPS and Galileo it provides free positioning signals, and most modern multi-constellation GNSS receivers track BeiDou alongside the others to improve fix availability and accuracy, especially in Asia. Using more constellations means more satellites in view and a lower dilution of precision.
BLE (Bluetooth Low Energy)
A short-range, low-power wireless protocol used in telematics for sensor connectivity, device provisioning, and proximity detection. Trackers use BLE to read tire pressure sensors, temperature tags, and driver ID beacons, and to communicate with a configuration app during installation. Its low power draw makes it suitable for battery-powered tags that must last months or years.
CAN bus
The Controller Area Network, the standard two-wire serial bus that connects the electronic control units inside a vehicle. A telematics device reads the CAN bus to extract odometer, fuel level, engine RPM, fault codes, and dozens of other signals directly from the vehicle rather than from add-on sensors. Reading it correctly across vehicle makes is non-trivial and is part of CAN bus and J1939 telematics work.
Cat-M1 / LTE-M
A low-power wide-area cellular technology in the LTE family, designed for IoT devices that need more bandwidth and mobility than NB-IoT. Cat-M1 supports voice, handover between cells while moving, and lower latency, which makes it well suited to mobile asset and vehicle tracking. It trades some of NB-IoT's deep-penetration and ultra-low-power advantages for that responsiveness.
CoAP
The Constrained Application Protocol, a lightweight request-response protocol that runs over UDP and is aimed at very constrained devices and lossy networks. With a compact 4-byte header and no persistent connection to maintain, it suits sleepy NB-IoT trackers that wake briefly to send a small report. Optional confirmable messages add acknowledgement when reliability is needed.
Dead reckoning
Estimating position by integrating motion (heading and speed from a gyroscope, accelerometer, and wheel or vehicle speed) when the GNSS signal is lost, such as in tunnels and multi-storey car parks. The receiver carries the last known fix forward using inertial data until satellites are reacquired. It bridges coverage gaps but accumulates error over time, so it is a short-term aid, not a replacement for GNSS.
Dwell time
The minimum duration an asset must remain inside a geofence before the entry is counted as significant. Dwell filters out drive-throughs and converts a raw boundary crossing into a meaningful stop, such as a bus that actually paused to board passengers. It is also used to measure detention time at yards and customer sites.
eCall
A European in-vehicle emergency call system that automatically dials the 112 emergency number and transmits a minimum set of data (location, time, vehicle identification) when a serious crash is detected, typically by airbag deployment. It is mandatory on new passenger car types in the EU. The telematics analogue in India is the panic and ERSS 112 integration required by AIS 140.
eDRX
Extended Discontinuous Reception, a cellular power-saving feature that lets a device stretch the interval between checks for incoming network pages. By sleeping longer between paging windows, the modem saves significant power while still being reachable within a bounded delay. It is a middle ground between always-listening and the deeper sleep of PSM.
ERSS 112
India's Emergency Response Support System reachable on the single number 112, into which AIS 140 panic alerts are routed. When a passenger presses the panic button on a compliant vehicle, the device sends an emergency alert that reaches the state emergency response centre. The integration path and message format are part of the AIS 140 requirements.
Galileo
The European Union's global navigation satellite system, providing free open-service positioning worldwide. It is designed for civilian control and offers high accuracy, and modern receivers track it together with GPS, GLONASS, and BeiDou. More constellations in view means faster, more reliable fixes.
Geocoding
Converting between geographic coordinates and human-readable addresses. Forward geocoding turns an address into a latitude and longitude; reverse geocoding turns a tracker's coordinates into a street address for a report or alert. Telematics platforms lean heavily on reverse geocoding so operators see "near 12 MG Road" instead of raw decimals.
Geofence
A virtual boundary in geographic coordinates paired with a rule that fires when a tracked asset enters or exits it. Fences can be circular, polygonal, or corridor-shaped, and are used for arrival detection, route deviation, and restricted-zone alerts. The geometry, noise handling, and scaling for these are covered as geofencing solutions.
GLONASS
Russia's global navigation satellite system, operational worldwide and one of the four major constellations. It uses a different signal scheme than GPS but is tracked alongside it by multi-constellation receivers, improving fix availability particularly at high latitudes. Combining GLONASS with GPS noticeably increases the number of usable satellites in urban environments.
GNSS
Global Navigation Satellite System, the umbrella term for all satellite positioning constellations: GPS, GLONASS, Galileo, BeiDou, and NavIC. A GNSS receiver may track several of these at once. Choosing and integrating the right receiver and antenna for a given environment is its own discipline, covered under GNSS module integration service.
GPS
The Global Positioning System, the United States satellite navigation constellation and the original mass-market GNSS, which is why "GPS" is often used loosely to mean any satellite positioning. Strictly it refers only to the US system. Most trackers today are multi-constellation and use GPS as one of several signal sources.
TERMS H TO O
H to O
HDOP
Horizontal Dilution of Precision, a number that describes how favorable the current satellite geometry is for a horizontal fix. When satellites are spread evenly across the sky, HDOP is low and the position is tight; when they are clustered or few, HDOP is high and the same measurement noise yields a much larger error. Telematics systems gate geofence and reporting decisions on HDOP to discard untrustworthy fixes.
J1939
An SAE standard that defines the higher-layer protocol running on CAN bus in heavy-duty vehicles such as trucks, buses, and off-highway equipment. It specifies how parameters like engine load, coolant temperature, and fuel rate are encoded into standardized parameter group numbers, so a reader can interpret signals consistently across manufacturers. Decoding it is part of CAN bus and J1939 telematics work.
MQTT
A lightweight publish-subscribe messaging protocol that runs over TCP and is the dominant choice for telematics device-to-cloud communication. Devices publish location and status to topics on a broker, and any number of backend services subscribe without the device knowing. It provides quality-of-service delivery levels, keepalive, and Last Will offline detection, with broker fleets implemented through MQTT cloud integration.
NavIC / IRNSS
India's regional navigation satellite system, formerly called IRNSS, providing positioning over India and a surrounding region. AIS 140 mandates NavIC support in commercial vehicle trackers, so receivers sold into the Indian market must track its L5 and S-band signals. Adding NavIC to a tracker affects receiver, antenna, and firmware choices, addressed in NavIC and IRNSS tracker development.
NB-IoT
Narrowband IoT, a low-power wide-area cellular technology optimized for devices that send small amounts of data infrequently and need deep indoor penetration and multi-year battery life. It does not support cell handover well, so it suits stationary or slow-moving assets rather than fast vehicles. Long-life asset trackers built on it are covered as part of NB-IoT asset tracker development.
OBD-II
The standardized On-Board Diagnostics port present in light vehicles, exposing engine and emissions data and a power feed through a 16-pin connector. Plug-in telematics dongles use it to read diagnostic trouble codes, speed, RPM, and fuel data without any wiring. Designing a reliable OBD device that works across vehicle makes is covered in OBD-II telematics device development.
OTA
Over-the-air updates, the mechanism for delivering new firmware or configuration to deployed devices remotely instead of physically touching each one. A robust OTA system uses a dual-bank flash layout, signature verification, and automatic rollback so a bad update cannot brick a device. AIS 140 requires OTA capability, and it is essential for patching security issues across a large fleet.
TERMS P TO Z
P to Z
Panic button
A physical emergency button wired into a vehicle tracker that, when pressed, sends an immediate high-priority alert to the backend and onward to emergency services. Under AIS 140 the panic button is mandatory and must route to the ERSS 112 system. Reliable panic handling means the alert has to fire even with poor connectivity, which drives store-and-forward and on-device logic.
PSM
Power Saving Mode, a cellular feature that lets a device tell the network it will be unreachable for a long period and then power down most of the modem while staying registered. It is the deepest cellular sleep state and is what enables NB-IoT trackers to reach multi-year battery life. The tradeoff is that the device cannot receive downlink commands until it next wakes on its own schedule.
Reefer
Industry shorthand for a refrigerated trailer or container, where telematics monitors set-point and return-air temperature, door events, and the refrigeration unit's run state to protect perishable and pharmaceutical cargo. A temperature excursion can spoil an entire load, so alerts must be fast and the audit trail complete. This is built as a dedicated reefer monitoring system.
Route corridor
A geofence shaped as a route polyline with a tolerance band on each side, used to detect when an asset leaves its planned path rather than whether it is inside an area. The inside test is the perpendicular distance from the asset to the nearest segment of the centerline. It is the foundation of route-deviation alerting for valuables transport and scheduled services.
RTK
Real-Time Kinematic positioning, a technique that uses carrier-phase measurements and a nearby base station or correction network to achieve centimeter-level accuracy, far beyond the meters of standard GNSS. It is used where precision matters, such as agriculture guidance, surveying, and lane-level positioning. It requires a correction data link and a capable receiver, so it is reserved for applications that genuinely need the accuracy.
RTLS
Real-Time Location System, a technology for tracking assets and people indoors where GNSS does not reach, typically using BLE, UWB, or Wi-Fi anchors. It fills the gap inside warehouses, factories, and hospitals, complementing outdoor GNSS tracking. Accuracy ranges from a few meters with BLE to tens of centimeters with UWB.
TCP
The Transmission Control Protocol, the reliable, ordered, connection-oriented transport that most telematics links sit on, either as a raw socket carrying a custom binary tracker protocol or beneath MQTT. TCP guarantees byte delivery and order but gives no concept of a message, so the application must define framing. Low-cost trackers like GT06 and Concox families speak custom binary protocols directly over TCP.
Telematics
The combination of telecommunications and informatics applied to vehicles and assets: capturing data from a device in the field and transmitting it to a backend for monitoring, analysis, and control. It spans the GNSS receiver, the sensors, the cellular link, the protocol, and the cloud platform. The whole stack is engineered under telematics and GPS tracking.
TTFF
Time To First Fix, how long a GNSS receiver takes to compute a usable position after power-on. A cold start with no prior data can take 30 seconds or more, while a warm or assisted start (using A-GNSS) can be a few seconds. Minimizing TTFF matters for battery-powered trackers that wake, fix, report, and sleep, and it depends heavily on the receiver and antenna chosen in GNSS module integration.
UWB
Ultra-Wideband, a short-range radio technology that measures distance by the precise time of flight of very wide-bandwidth pulses, achieving location accuracy of tens of centimeters indoors. It is used in high-precision real-time location systems where BLE accuracy is not enough, such as tracking forklifts and tools on a factory floor. The cost is more expensive anchors and tags than BLE.
VLTD
Vehicle Location Tracking Device, the AIS 140 term for the in-vehicle unit that captures GNSS position and vehicle data, supports a panic button, and reports to a backend control centre. A compliant VLTD must support NavIC, OTA updates, and emergency alerting, and must pass ARAI or ICAT certification. These are designed and certified as the AIS 140 GPS tracking device for India.
FAQ
Frequently Asked Questions
What is the difference between GPS and GNSS?
GPS is the United States satellite navigation constellation specifically. GNSS is the umbrella term covering all constellations, including GPS, GLONASS, Galileo, BeiDou, and NavIC. People often say GPS loosely to mean any satellite positioning, but most modern trackers are multi-constellation GNSS receivers that use several systems at once for faster, more reliable fixes.
What does VLTD mean in AIS 140?
VLTD stands for Vehicle Location Tracking Device, the AIS 140 term for the in-vehicle unit that captures GNSS position and vehicle data, supports a panic button, and reports to a backend control centre. A compliant VLTD must support NavIC, over-the-air updates, and emergency alerting through ERSS 112, and must pass ARAI or ICAT certification.
What is the difference between NB-IoT and Cat-M1?
Both are low-power wide-area cellular technologies. NB-IoT is optimized for stationary devices that send small amounts of data infrequently with deep indoor penetration and multi-year battery life, but handles handover poorly. Cat-M1, also called LTE-M, offers more bandwidth, lower latency, voice support, and proper handover, making it the better fit for moving vehicles and assets.
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Related pages
Engineering Across Every Term in This Glossary
From GNSS receiver selection and NavIC compliance to CAN bus decoding, MQTT broker fleets, and geofencing, the full telematics stack is covered. If a term here describes something you are trying to build, support is available.
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