MRTKLIB v0.4.4 Release Notes¶

Release date: 2026-03-09 Type: Feature (dual-channel CLAS real-time PPP-RTK) Branch: feat/rtkrcv-clas-2ch

Overview¶

v0.4.4 adds dual-channel (2ch) CLAS L6 support to rtkrcv real-time positioning. The unused base-station stream slot (stream index 1) is repurposed as a second L6 correction input, enabling rtkrcv to process two independent CLAS L6D streams simultaneously — matching the post-processing engine's dual-channel capability.

Highlights¶

• 2ch CLAS real-time — rtkrcv now accepts two L6 correction streams: stream 3 carries L6 ch1, stream 2 (base slot) carries L6 ch2. The CLAS channel is derived from the stream index automatically.
• CTest rtkrcv_rt_clas_2ch — Automated regression test replaying 1 hour of 2-channel BINEX+L6 data at 10x speed (~372s wall time).
• Minimal code change — Only 2 lines changed in mrtk_rtksvr.c; the existing CLAS_CH_NUM=2 infrastructure handles the rest.

Performance: Single-Channel vs Dual-Channel Real-Time¶

Single-channel (2019/239 dataset, v0.4.3)¶

Dual-channel (2025/157 dataset, v0.4.4)¶

Analysis¶

• The 2025/157 dataset is inherently more challenging than 2019/239 (PP fix rate 88% vs 99.86%), so the RT fix rate gap is expected.
• The RT 2ch fix rate (67.4%) is lower than PP (88%) primarily due to real-time stream synchronisation: L6 ch1 and ch2 corrections arrive via independent streams, and the correction merge timing is less optimal than in post-processing where both channels are read synchronously per epoch.
• All 3,600 epochs produce valid solutions (only 17 SPP during initial convergence).

What Changed¶

Stream-to-Channel Mapping (mrtk_rtksvr.c)¶

The CLAS channel assignment was changed from hardcoded ch=0 to stream-index-derived:

int ch = (index == 1) ? 1 : 0;  /* index 1 (inpstr2)→ch1, index 2 (inpstr3)→ch0 */

This applies to both the direct CLAS decode path and the UBX/L6E redirect path. The existing rate limiter, week_ref initialisation, and bank/grid update logic all work per-channel without modification.

Design: Base Stream Repurposing¶

In PPP-RTK mode, stream index 1 (base station) is unused. Rather than extending rtksvr_t with a 4th input stream (which would require significant structural changes), the base slot is repurposed for L6 ch2:

Configuration (rtkrcv_2ch.conf)¶

Key differences from single-channel rtkrcv.conf:

inpstr2-type   =file           # was: off
inpstr2-path   =...ch2.l6::T::x10
inpstr2-format =clas           # was: (empty)

Test Suite (59 tests)¶

59 total tests (58 from v0.4.3 + 1 new rtkrcv_rt_clas_2ch).

Files Changed¶