Terra — nationwide measurement
What the sky is doing to precision GPS, right now.
Hundreds of NOAA ground stations record the ionosphere over the United States every hour. Terra reads them and turns the churn into one reading per area — measured, not modelled.
Reading…
Loading the latest measured hour.
The measurement is not available right now.
Thresholds are TECU per minute above a normal hour, and are read from the published data rather than set here.
Still calibrating. Two things are settling: which stations make the final network, and exactly where the lines between clear, elevated and disturbed sit. Every value on this map is a real measurement — the boundaries drawn on them are provisional and will move as they are fitted.
By region
Fourteen regions, one reading each.
A region’s reading is the 75th percentile of the areas inside it — so it turns elevated when a meaningful minority of it does, not when its average finally does.
The stations
Where the numbers come from.
Terra reads NOAA’s Continuously Operating Reference Stations — permanent GPS receivers bolted to the ground and published free. These are the ones in the current set, chosen for coverage, data quality and how promptly they publish. Every vendor map is built on something; this is ours, in full.
| Site | State | Operator | Data complete |
|---|---|---|---|
| Loading the station list… | |||
— · full list published as stations.json
How to read it
What is measured
How fast and how unevenly the ionosphere is churning overhead, in TECU per minute. A smooth sky cancels out of a corrected GPS fix. A churning one does not, and the failure is quiet — the rover keeps reporting that everything is fine.
Why blank stays blank
An area with no station reporting is drawn as a hatch and never coloured in. Where a reading is carried in from neighbours, it is hatched, dimmed and labelled as an estimate. A confident colour over ground nobody measured is the fastest way to lose your trust.
This is not a forecast
Everything here is a measurement of an hour that has already happened, published as soon as the stations finish it. Terra does not yet publish a forecast, and will not claim accuracy it has not scored in public.
| Area | Region | Reading | Tier | Confidence | Source |
|---|