XRain provides satellite precipitation data (more info). This data is not measured directly like rain gauge data is, and therefore will never be as accurate as an appropriately-installed rain gauge.
Beyond this, the key limitations of the dataset are:
- Spatial resolution (grid size) of 0.1° by 0.1°; roughly 11 km by 11 km at the equator and 6 km by 11 km at ± 60° latitude
- Time step length of 30 minutes, but based on periodic near-instantaneous measurements as satellites orbit the earth
- Incomplete above 60° N and below 60° S (for this reason XRain does not provide data above 60° N and below 60° S)