GNSS-SDR v0.0.21 released

April 14, 2026 3 minute read

This release provides bug fixes and new features. Most relevant changes with respect to the former release are listed below:

Improvements in Availability:

Introduced a histogram-based navigation data bit synchronizer used by tracking loops to robustly detect navigation-bit transitions in signals without secondary code. Lock is declared when the histogram exhibits a clearly dominant phase bin, verified using a configurable dominance ratio and stability criterion. Once synchronized, the tracking loop can safely switch to extended coherent integration, improving tracking sensitivity and TTFF. New configuration parameters are Tracking_1C.bs_dominance_ratio (ratio between the count of the dominant histogram bin and the total number of detected transition events, default: 0.6), Tracking_1C.bs_stable_best_required (required number of consecutive evaluations with the same dominant histogram bin, default: 3), and Tracking_1C.bs_min_events_for_lock (minimum number of detected transition events before lock evaluation, default: 10).

Enabled multi-band processing off-loading to the FPGA when using the MAX2771 RF front-end.
Added a new Signal Source implementation NTLab_File_Signal_Source, which is able to read files grabbed from NTLab RF front-ends.
Improved Labsat_Signal_Source by fixing multi-channel file reading from LabSat 3 recordings and adding initial support for LabSat 4.
Improvements in Glonass L1/L2 C/A signal tracking and decoding of the GNAV message.
Added a cycle-slip detector, with events reported in internal logging and RINEX observation files. This introduces a new field in Gnss_Synchro and in the corresponding .proto definition.
Improved tracking of GPS L2C(M) signals.
Fixed GPS L1 decoding failure when pull_in_time_s is too short.
Improved processing chain for BeiDou B1I and B3I signals.
Added processing chains for the Quasi-Zenith Satellite System (QZSS), Japan’s regional navigation satellite system, supporting L1 C/A and L5 signals.

Added a CI job to detect lines longer than 512 characters (avoid this lintian tag warning).
Added formatting of .proto files with clang-format. Added check in CI job.
Major refactoring of the GNSSFlowgraph and GNSSBlockFactory class implementations, greatly improving maintainability, simplifying the addition of new signals, and eliminating a lot of duplicated code. Awesome contribution by @MathieuFavreau.
Major refactoring of the acquisition adapters and GNU Radio blocks, improving maintainability and extensibility. Another excellent contribution by @MathieuFavreau.
Refactoring of Telemetry Decoder adapters for better maintainability.
Refactored the internal handling of multi-signal configurations in the PVT block for improved maintainability and extensibility. Another excellent contribution by @MathieuFavreau.
Major refactoring of the RINEX printer, significantly improving maintainability and correcting several bugs. The printer now consistently populates all observable fields when multiple signals exist for the same constellation, writing zeros for missing observables as needed to strictly match the observables header format. Another excellent contribution by @MathieuFavreau.
Integration of Glonass L1/L2 C/A signal tracking into the main tracking engine. Removed GLONASS_L1_CA_DLL_PLL_C_Aid_Tracking and GLONASS_L1_CA_DLL_PLL_C_Aid_Tracking Tracking block implementations, replaced by GLONASS_L1_CA_DLL_PLL_Tracking and GLONASS_L1_CA_DLL_PLL_Tracking.

Fixed building option -DENABLE_ION=ON when using CMake >= 4.0.
Updated gsl-lite to v1.0.1. See the gsl-lite release.
Updated local cpu_features library to v0.10.1.
Allow linking against Boost 1.89.0.
Added implementations of several volk_gnsssdr kernels for the RISC‑V Vector (RVV) instruction set. Awesome contribution by @BigTurtle8 (Marcus Alagar) as part of Google Summer of Code 2025.

Added a Python-based GNSS skyplot visualization utility at utils/skyplot/skyplot.py, which generates a skyplot from a RINEX navigation file and saves the image in usual image formats. It requires numpy and matplotlib.
Added a Python-based OSNMA timeline viewer visualization utility at utils/osnma-log-viewer/osnma_log_viewer.py, which generates a plot from a GNSS-SDR log file containing OSNMA messages. It requires matplotlib and pandas.
File_Signal_Source fixed file length and sample skip calculations on 32-bit systems.
Fixed tracking the same PRN in multiple channels. Previously, this could happen when the number of acquisition channels was close to the number of available PRNs for a given signal.
Added a new global configuration parameter, GNSS-SDR.tow_to_trk. When set to true, Telemetry blocks send asynchronous messages back to the Tracking blocks containing the information required to compute the TOW and week number at the tracking stage. The default value is false.
Fixed a long-standing issue in which acquisition blocks still blocked execution even when blocking=false was specified in the configuration.