The ionosphere is the largest remaining error source affecting GNSS regional augmentation system.The situation could be more serious whenthere is no enough measurement ina limited areas monitored by the network.The spatial threat model is constructed to restrict the ionospheric behavior under these under-sample scenarios for a more stringent bound.In this worktwo ionosperhic spatial threat model,namely ‘blob’ and ‘wall’models are constructed.In the ‘blob’ model,ionospheric delay increase with radius of ‘blob’ until the saturation is reached at a distance of 500Km.In the ‘wall’ model,ionospheric delay increase with the distance of ionospheric grids to ‘wall’.Different ionospheric behavior during the storm for China area and North America area is responsible for the different model variation.