22 terms explained without the jargon — what they mean, why they matter, and how they affect whether your alerts can be trusted.
Boundaries, shapes, and the geometry of deciding what is inside.
Dwell time is how long a device remains inside a geofenced zone, and by extension the minimum duration a crossing must persist before it counts as real.
Geofence hysteresis is the use of different thresholds for entering and leaving a zone, so a device hovering at the boundary cannot rapidly flip between states.
Geofencing is the practice of drawing a virtual boundary around a real-world place and having software react when a tracked device crosses it.
A GeoJSON polygon is the standard way to describe an area on a map as a list of coordinates, defined by RFC 7946 and understood by nearly every mapping tool.
Live tracking shows a device's position updating on a map in near real time — useful when you already know something is wrong, and poor at telling you that it is.
Point-in-polygon is the geometric test that decides whether a coordinate falls inside a shape — the core calculation behind every geofence check.
How devices work out where they are, and how wrong they can be.
A-GPS (Assisted GPS) speeds up position fixes by downloading satellite orbit data over the mobile network instead of waiting to receive it from the satellites themselves.
A cold start is a GPS receiver powering on with no usable satellite data, forcing it to download orbit information slowly from the satellites themselves.
GNSS is the umbrella term for all satellite navigation systems — GPS, Galileo, GLONASS, and BeiDou — of which GPS is only the American one.
GPS accuracy is how close a reported position is to the true location, usually expressed as a radius within which the real position probably falls.
GPS drift is the apparent movement of a stationary device caused by errors in its reported position rather than by any real change in location.
HDOP measures how favourably satellites are arranged in the sky, acting as a multiplier on positioning error — the same measurements give a far worse fix when satellites are clustered.
LBS positioning estimates a device's location from nearby mobile network towers rather than satellites — far less accurate than GPS, but it works indoors and needs no fix.
Turning boundary crossings into messages people actually trust.
Alert debouncing is the practice of suppressing repeat notifications for a condition that is already active, so a single real event produces a single alert.
An enter alert is a notification sent when a tracked device arrives in a geofenced zone — the arrival counterpart to an exit alert.
An exit alert is a notification sent when a tracked device leaves a geofenced zone during a period when that zone is being monitored.
A recovery alert is a notification sent when a previously alerting condition returns to normal — telling you a situation resolved without you having to check.
SIMs, identifiers, and getting a tracker onto the network.
An APN (Access Point Name) is the setting that tells a SIM-equipped device which gateway to use for mobile data — and the most common reason a GPS tracker never reports.
GPRS is the 2G-era mobile data service that most budget GPS trackers still use to send positions — and which is being switched off network by network.
An IMEI is the 15-digit serial number that uniquely identifies a mobile device, and on most GPS trackers it doubles as the only credential the device presents to a server.
The reporting interval is how often a tracker sends its position to a server — the single setting that most directly trades battery life against how quickly you learn about a boundary crossing.
Telematics is the combination of telecommunications and vehicle data — sending information about how a vehicle is being driven, not just where it is.
Most glossaries in this industry paraphrase each other. These entries are written from building a geofencing service — so where a term touches something we had to make a real decision about, the entry says what we decided and why.
Alert debouncing and recovery alerts describe the actual state machine behind Geoblip's notifications. GPS drift explains the problem that machine exists to solve. If you would rather try the ideas than read about them, the free tools are a faster route.