Method for performing a correction of an ionospheric error affecting pseudo-range measurements in a GNSS receiver, corresponding receiver apparatus and computer program product

A global navigation satellite system (GNSS) receiver, comprising:

• one or more processors;
• and
• one or more memories configured to store software instructions, wherein the one or more processors are configured to execute the software instructions to perform a process for correcting an ionospheric error affecting pseudo-range measurements in the GNSS receiver receiving a plurality of satellite signals from a plurality of satellites of a constellation of satellites, the process including:
• receiving pseudo-range measurements previously calculated by the GNSS receiver obtained from a first carrier signal and a second carrier signal in the satellite signals in GPS bands L1 and L5;
• and
• performing a correction procedure of the pseudo-range measurements including:
• compensating the pseudo-range measurements for predictable errors obtaining corrected pseudo-ranges;
• and
• applying to the corrected pseudo-range measurements a further calculation to obtain further ionospheric error correction values;
• performing a position calculation operation processing the corrected pseudo-range measurements and the ionospheric error correction values and outputting position, velocity and time information of the GNSS receiver;
• wherein applying to the corrected pseudo-ranges a further ionospheric error correction calculation to obtain further ionospheric error correction values includes:
• performing one or more checking operations enabling performing an ionosphere free linear combination on the pseudo-range measurements obtaining ionospheric free linear combination pseudo-range measurements and supplying the ionospheric free linear combination to the position calculation operation only;
• and
• otherwise performing a standard ionospheric error correction derived from GNSS navigation data by Klobuchar/Nequick models and/or satellite-based augmentation system (SBAS), supplying the correspondingly standard ionospheric corrected pseudo-range measurements to the position calculation operation, wherein performing one or more checking operations includes evaluating a solar activity and enabling performing the ionospheric free linear combination if the solar activity is above a given threshold;
• wherein the evaluating a solar activity and enabling performing the ionospheric free linear combination if the solar activity is above a given threshold includes:
• receiving as input the pseudo-range from the first carrier or second carrier and the ionospheric free linear combination pseudo-range measurements;
• calculating a dual frequency estimated ionospheric error correction for a given satellite as the difference between the pseudo-range from the first carrier or second carrier and the ionospheric free linear combination pseudo-range measurements;
• and
• calculating a correction difference as the difference of the dual frequency estimated ionospheric error correction for the i-th satellite with respect to a broadcasted correction, calculated as standard ionospheric error correction derived from GNSS navigation data by Klobuchar/Nequick models and/or SBAS.

A method, comprising:

• receiving, at a global navigation satellite system (GNSS) receiver, pseudo-range measurements in a plurality of satellite signals from a plurality of satellites;
• generating corrected pseudo-range measurements by compensating for predictable errors in the pseudo-range measurements;
• generating ionospheric error correction values from the corrected pseudo-range measurements by generating ionospheric free linear combination pseudo-range measurements by performing an ionosphere free linear combination on the pseudo-range measurements;
• and
• performing a position calculation by processing the corrected pseudo-range measurements and the ionospheric error correction values;
• and
• outputting position, velocity and time information of the GNSS receiver based, at least in part, on the position calculation operation;
• applying to the corrected pseudo-range measurements a further ionospheric error correction calculation to obtain further ionospheric error correction values, including:
• performing one or more checking operations enabling performing an ionosphere free linear combination on the pseudo-range measurements obtaining ionospheric free linear combination pseudo-range measurements and supplying the ionospheric free linear combination to the position calculation operation only;
• and
• otherwise performing a standard ionospheric error correction derived from GNSS navigation data by Klobuchar/Nequick models and/or satellite-based augmentation system (SBAS), supplying the correspondingly standard ionospheric corrected pseudo-range measurements to the position calculation operation, wherein performing one or more checking operations includes evaluating a solar activity and enabling performing the ionospheric free linear combination if the solar activity is above a given threshold;
• and
• checking if the GNSS receiver is in an urban environment including inputting standard pseudo-range measurements to a least square regression operation to calculate raw user position data from pseudo-ranges data, supplying residual errors for each pseudo-range measurement derived from the least square calculation, picking the maximum error value among such residual errors, performing a low pass filtering, in particular infinite impulse response filtering, on the maximum residual error value obtaining a urban environment indication value, checking if the urban environment indication value is greater than a respective threshold in the affirmative detecting, and signaling that the receiver is in an urban condition, otherwise an open sky condition is detected and signaled.