Ten sources.
None of them ours.

A fictional blend of national weather stations, airport sensors and private masts. Each station carries a siting grade, so a sheltered sensor never outvotes an exposed one. Tripline reads the three nearest stations to a cell and weights them by distance and grade.

A fictional composite of overlapping weather radars, corrected for beam height and for ground clutter. It gives the rain and wind fields between stations, which is where a cell reading would otherwise be a guess.

Index data from public sources such as the geostationary imagery published by NOAA. Satellites see a whole storm at once, which makes them the tie-breaker when two ground sources disagree. Not a partner of Tripline Underwriting Ltd; named as an example of a public source.

Index data from public sources such as the earthquake catalogue published by the US Geological Survey. Each event has an automatic solution first and a reviewed one later; a Tripline policy states which of the two it pays on. Not a partner of Tripline Underwriting Ltd; named as an example of a public source.

Index data from public sources such as the ERA5 reanalysis of the Copernicus programme. It blends decades of observations into a consistent record. Tripline uses it to price a cell against its past, and to check a live reading against what the atmosphere was expected to do. Not a partner of Tripline Underwriting Ltd; named as an example of a public source.

A fictional network of staff gauges and pressure sensors on rivers, with a warning level set by each river authority. A gauge that goes silent is replaced in the policy schedule by the next gauge along the same river, and the swap is recorded in the settlement note.

A fictional aviation feed that reports scheduled and actual gate times for each named flight, together with cancellations and diversions. Tripline compares it with the airport's own record and takes the later arrival of the two.

A fictional regional array that gives a second, independent magnitude for events near an insured location. A policy pays only when this value and the public catalogue agree within 0.3 magnitude units, or waits for the reviewed solution.

A fictional set of moored buoys that measure wind, pressure and wave height offshore. They are the only direct measurement of a storm before landfall, which is why the 36-hour alert reads them first.

A fictional network of ground temperature and rain sensors placed by growers and building owners. Siting is inspected once a year. It adds density in the places where official stations are far apart, and is used to cross-check, never alone.