Why do two lightning maps show different strikes?

01

Why do strike counts differ between trackers?[1][2]

Because the networks are measuring different things. Ground-based systems detect the radio emission from a discharge, while satellite instruments detect the optical flash. A single lightning event can register as one flash on one system and several strokes on another.

A flash is not a single event. Most cloud-to-ground flashes contain several return strokes down the same channel within a fraction of a second. Whether a network reports that as one flash or four strokes is a grouping decision made in software, and networks make it differently.

That alone can produce a threefold difference in a headline strike count for the same storm, with neither network being wrong. Comparing totals across sources is only meaningful if you know both grouping rules.

02

Does detection method change what gets seen?[1][2]

Substantially. Low-frequency ground networks detect cloud-to-ground strikes well and intracloud flashes poorly. Satellite optical sensors see both but only where cloud tops are visible, and they cannot resolve whether a flash reached the ground.

This is why a map showing far more activity than another is not necessarily better. It may simply be counting intracloud flashes that the other filters out, which matters if you are using the map to judge ground strike risk.

VLF/LF ground networks

Long detection range, strong on cloud-to-ground, weaker on intracloud. Position from arrival-time differences

VHF mapping arrays

Map the channel in three dimensions in fine detail, but only over a small regional footprint

Satellite optical sensors

Uniform coverage over whole hemispheres, sees flash tops, cannot distinguish ground contact

03

Why do positions differ for the same strike?[1]

Position accuracy depends on how many stations detected the flash and how they are arranged around it. A strike surrounded by stations is located to within a few hundred meters. One at the edge of a network, detected by distant stations in a poor geometric spread, can be off by several kilometers.

The geometry effect is the same one that limits GPS accuracy when satellites are clustered in one part of the sky. Timing differences pin down location well when the receivers surround the source and poorly when they all sit on one side of it.

Practically, this means strike positions over well-instrumented regions like western Europe or the continental US are far tighter than positions over oceans, deserts or polar regions, where the nearest stations may be thousands of kilometers away.

04

Which map should you trust?[1][3]

For safety decisions, none of them on their own. Use whichever map has good station density where you are, cross-check the trend rather than individual dots, and let thunder override the screen. Detection networks are informational rather than life-safety systems.

Every public lightning map carries a version of that disclaimer, and it is not boilerplate. These networks were built for research and for broad situational awareness, and their operators are explicit that they should not be the basis for protecting life or property.

The useful posture is to treat a lightning map the way you would treat a train departure board: informative, usually right, and not something to stand on the tracks for.