Ionospheric delay is one of the main error sources of positioning and timing of single-frequency satellite navigation users. BeiDou Navigation Satellite System broadcasts ionospheric parameters in the navigation message to facilitate users to correct ionospheric delay errors. BII/B3I signals provide Klobuchar model parameters. BIC/B2a signals provide BDGIM ionospheric model parameters.
Using global observation data to solve the precise ionospheric delay can achieve higher accuracy (2-9TECU).