Space based augmentation systems and methods using ionospheric bounding data to determine geographical correction source

A method for determining a corrections source in a space based augmentation system (SBAS), comprising:

• receiving ionospheric mask messages from a first GEO satellite;
• dynamically analyzing the ionospheric mask messages to determine a first abbreviated bounding region for a group of ionospheric grid points;
• determining a position of the GPS device;
• and
• determining whether the position of the GPS device is within the first abbreviated bounding region.

A computer-readable medium having computer-executable instructions adapted to:

• receive GPS data;
• receive an SBAS signal from a first correction source, the SBAS signal containing a number of ionospheric mask messages, each ionospheric mask message including a number of ionospheric mask bits with each bit representing a single ionospheric grid point in a single ionospheric band;
• analyze the ionospheric mask messages;
• and
• construct an abbreviated bounding region around a group of similar type ionospheric grid points.

A data structure for use by a global positioning system (GPS) device in making space based augmentation system (SBAS) corrections, comprising:

• a field representing an SBAS satellite identity;
• and
• a field representing an abbreviated bounding region around a group of similar type grid points in an SBAS signal;
• wherein the field representing the abbreviated bounding region is derived from a number of ionospheric mask messages, each ionospheric mask message having a data structure including:
• a field representing an SBAS satellite identity;
• a field representing an index of band;
• a field representing an issue of data indicator;
• and
• a field containing a number of ionospheric mask bits with each mask bit representing a single grid point in a single ionospheric band, and each mask bit indicating whether SBAS correction data is being provided by the SBAS satellite identity for that grid point.

A Global Positioning System (GPS) device, comprising:

• a processor;
• a memory adapted to communicate to the processor;
• a GPS receiver adapted to receive GPS signals and Space Based Augmentation System (SBAS) signals including a number of ionospheric mask messages;
• and
• wherein the device is operable to dynamically construct an abbreviated bounding region around a group of similar type grid points contained in the number of ionospheric mask messages.