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Frequently Asked Questions

Glossary — lightning & weather terms

Lightning

A sudden electrostatic discharge between electrically charged regions of a cloud, between clouds, or between a cloud and the ground.

Cloud-to-ground (CG) lightning

A lightning discharge that occurs between a thundercloud and the ground — the type most relevant to safety on the surface.

Intra-cloud (IC) lightning

A lightning discharge that occurs within a single cloud, between its charged regions; the most common form of lightning.

Stroke

A single electrical discharge within a lightning flash. One flash can contain several strokes along the same channel.

Flash

The complete lightning event a viewer perceives, made up of one or more strokes.

Sferic

The broadband radio-frequency pulse (atmospheric) emitted by a lightning discharge, used by detection networks to locate strikes.

Blitzortung.org

A free, community-run lightning-location network of volunteer receiving stations whose real-time data powers ZAPPOLLO’s free lightning feed.

Time of Arrival (TOA)

A locating method that uses the precise time each station receives a strike’s radio pulse; differences in arrival time pinpoint the source.

Multilateration

Computing a position from the differences in signal arrival times at multiple known station locations.

Triangulation

Determining a location from the intersection of directions or ranges measured from several reference points.

Detection efficiency

The fraction of actual lightning events a network successfully detects in a given area — higher where station coverage is dense.

Thunderstorm

A storm characterised by lightning and thunder, typically produced by cumulonimbus clouds, often with heavy rain, gusty wind and sometimes hail.

Nowcasting

Very short-term weather forecasting (minutes to a few hours) based on the latest observations such as radar and lightning.

Precipitation

Any form of water — rain, snow, sleet or hail — that falls from clouds to the ground; available as a weather layer in ZAPPOLLO.

Radar (weather)

A remote-sensing system that detects precipitation intensity and movement; ZAPPOLLO’s rain radar layer is provided by RainViewer.

Terminator (day/night line)

The moving boundary between the sunlit (day) and dark (night) sides of the Earth, drawn on the ZAPPOLLO globe.

Sentinel-2

An Earth-observation satellite mission whose cloudless composite imagery provides ZAPPOLLO’s satellite base map.

OpenStreetMap (OSM)

A free, collaborative world map database that provides the geographic base data for ZAPPOLLO’s map tiles.

MapLibre GL

The open-source rendering engine ZAPPOLLO uses to draw fast, interactive vector and raster maps, including the 3D globe.

Globe projection

A map view that renders the Earth as a 3D sphere rather than a flat plane, preserving its true round shape.

Mercator projection

A flat cylindrical map projection that preserves local angles but increasingly exaggerates area toward the poles; ZAPPOLLO’s flat-map mode.

Heatmap

A visualisation that uses colour intensity to show the density or frequency of events — here, concentrations of lightning strikes.

IndexedDB

A browser database that lets ZAPPOLLO store recent lightning strikes locally so the history timeline works without a server.

Progressive Web App (PWA)

A website that can be installed and used like a native app, with offline support and a home-screen icon.

Atmosphere halo

The glowing rim of scattered light rendered around the ZAPPOLLO globe to mimic the look of Earth’s atmosphere from space.

Strike rate

The number of detected lightning strikes per unit of time (per second or per minute), shown live in ZAPPOLLO as a measure of storm intensity.