What Is GOES-GLM? How NOAA Detects Lightning From Space
The Geostationary Lightning Mapper on NOAA's GOES satellites detects lightning across the Americas from 22,000 miles up. Here is how it works and why it powers StrikeCast.
Lightning detection from orbit
GLM stands for Geostationary Lightning Mapper, an instrument flying on NOAA's GOES weather satellites. GOES satellites sit in geostationary orbit about 22,000 miles above the equator, which means they hover over the same patch of Earth and watch it continuously.
From that vantage point, the GLM stares at the full disk of the Americas day and night, looking for the brief optical flashes that lightning produces — including the in-cloud flashes that ground-based networks often miss.
How the instrument sees a flash
The GLM is essentially a very fast, specialized camera. It captures hundreds of frames per second and watches for a specific wavelength of light that lightning emits as it punches through cloud tops.
When a flash brightens a pixel above the background glow of sunlit clouds, the instrument records it with a timestamp and location. Because it watches the whole hemisphere at once, it does not wait for a storm to pass over a fixed sensor — it sees strikes the moment they happen, anywhere in view.
Two satellites, GOES-East and GOES-West, together cover the entire continental United States, giving full-CONUS coverage with no gaps over remote terrain or open water.
Strengths, limits, and accuracy
GOES-GLM is US-government data, free and in the public domain. Its great strength is uniform coverage: every part of the country is watched equally, and total lightning (in-cloud plus cloud-to-ground) is detected.
The trade-off is spatial precision. Satellite geolocation places a strike within roughly 8 to 14 kilometers, which is why StrikeCast displays the hero distance as a rounded, honest figure rather than implying false precision. For knowing whether a storm is two miles away or twenty, that is more than enough.
How StrikeCast uses it
StrikeCast ingests GOES-GLM strikes in near real time, then computes the distance from your location to the nearest one and the approaching or moving-away trend. The same logic drives the push alerts.
The client never talks to a lightning provider directly and never sees a raw data source name on screen — it only receives distance, trend, and strikes through our backend. And because detection is satellite-based, your phone does not need to track you in the background. Your location stays on your device: never shared, never tracked.
See the live distance to the nearest strike and get free alerts when lightning approaches — powered by NOAA satellite data. Never shared, never tracked.
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Frequently asked
What does GLM stand for?
GLM is the Geostationary Lightning Mapper, an instrument on NOAA's GOES weather satellites that detects lightning across the Americas from geostationary orbit.
How accurate is GOES-GLM lightning detection?
GOES-GLM geolocates strikes within roughly 8 to 14 kilometers. That is why StrikeCast shows distance as a rounded figure — accurate enough to tell whether a storm is close or far without implying false precision.
Is GOES-GLM data free?
Yes. GOES-GLM is NOAA US-government data in the public domain, which is why StrikeCast can offer nationwide lightning tracking without ads or selling your data.
More guides on the StrikeCast lightning safety hub.