1 Revision History

Version	Date	Notes
1.0	2026-09-27	Initial publication.

This edition was produced and first published about 4 month(s) after the end of the reporting period, as part of completing the monthly series. The methodology, inputs and processing are the same as for the editions published on schedule.

2 Introduction

This monthly report summarises the observation-quality state of the GEONET (GNSS Earth Observation Network) reference-station network operated by the Geospatial Information Authority of Japan (GSI), for May 2026. It is the free-tier deliverable of the PNT Moni monitoring service: a national, aggregate view that lets operators, researchers and users of GNSS-augmentation services see how the underlying observation infrastructure performed.

The report is intentionally limited in scope. It does not include:

Per-station drill-downs or named station lists (Pro-tier).
Positioning-domain accuracy or TTFF results — those appear in the full Monthly Report.
Integrity indicators, ionospheric/tropospheric correction diagnostics, or cross-engine comparisons (Phase 1+).

The data and methods used to produce this report are openly documented and reproducible from publicly available GEONET inputs. §Methodology below summarises them; the full methodology document is [https://pntmoni.com/methodology/qc/v1.2.0](https://pntmoni.com/methodology/qc/v1.2.0).

3 Methodology

This section summarises the methodology; the full document is [https://pntmoni.com/methodology/qc/v1.2.0](https://pntmoni.com/methodology/qc/v1.2.0).

Data sources (methodology §2): GEONET RINEX 3.02 observation and broadcast-navigation files (30-second sampling, 24-hour daily files), retrieved from GSI’s archive under the Public Data License 1.0. All 1,298 continuously-operating GEONET reference stations active for May 2026 are included.

QC pipeline (methodology §3):

RINEX 3 (GEONET)
  ↓ convbin (RTKLIB 2.4.2)            v3 → v2.11 conversion
  ↓ teqc 2019Feb25                    +qc -R +L2C_L2 +L5
  → .{yy}S summary per station/day
  ↓ pntmoni-pipeline qc summarize     parse + wide Parquet
  → data/processed/qc_summary/...     1 row × 639 cols per station-day

QZSS LNAV broadcasts use the post-2024 health-flag encoding of IS-QZSS-PNT-006 §4.1.2.3(4); the pipeline masks the L1C/B health bit before passing the QNAV to teqc so that L1C/A-broadcasting QZS satellites are correctly QC’d (methodology §2.1).

Metrics (methodology §4): the four core families established in Shiono & Kubo (2025) (ION GNSS+ 2025) and extended in Shiono & Kubo (2026) (NAVIGATION, doi:10.33012/navi.762) — Visibility, SNR, Multipath, and Cycle Slips — plus data availability. The Galileo E5b family (SN7, MP17, MP71) is reported as informative reference only, not part of the absolute-evaluation baseline. Symbol-by-symbol definitions are in the Appendix glossary.

Aggregation (methodology §5): all multipath, SNR and slip figures are computed from teqc’s 5° elevation bins with an elevation mask of 15° applied (15 of 19 bins kept); multipath/SNR values are obs-count weighted across the kept bins, slip totals are summed. This matches both Shiono & Kubo (2025) and the elmask used by the positioning engines (CLASLIB, RTKLIB).

3.1 Evaluation Network

Figure 1: GEONET reference stations covered in this report.

4 Executive Summary

Table 1

Metric	May 2026
National data availability (epoch coverage, daily mean)	99.98 %
National visibility (>10° track completeness, daily mean)	95.70 %
L1 C/A multipath — station-month median	0.200 m
L1 C/A SNR — station-month median	43.8 dB-Hz
Stations reporting	1,298
Days covered	31

Tip

Bottom line. The GEONET network operated at high observation fidelity throughout May 2026, with the headline metrics tracking expectations for a healthy reference network. See §National Overview for the distributions and trends behind these summary numbers.

5 National Overview — Observation Quality

5.1 Data Availability & Visibility

5.1.1 Data Availability

Epoch-level coverage: did the station log data every 30 seconds?

Figure 2: Data availability — fraction of the 2,880 nominal daily epochs with logged observations.

Table 2

Statistic	Station-monthly data availability
5th percentile	100.00 %
Median	100.00 %
95th percentile	100.00 %
Best station	100.00 %
Worst station	89.80 %

5.1.2 Visibility (可視率)

Sat-track completeness above 10° elevation: when the station was up, did it actually track the satellites it should have seen?

Figure 3: Visibility — Complete obs / Possible obs above 10° elevation, per teqc.

Table 3

Statistic	Station-monthly visibility
5th percentile	86.60 %
Median	97.17 %
95th percentile	99.65 %
Best station	99.86 %
Worst station	76.41 %

5.2 Distribution of Metrics

5.2.1 Signal-to-noise ratio

Figure 4: SNR distributions — L1 C/A and L5 (Shiono & Kubo 2025 core baseline).

Figure 5: SNR distributions — L2 (core) and Galileo E5b (reference; not part of the absolute-qualification baseline).

5.2.2 Multipath

Figure 6: Multipath RMS distributions — L1/L2 pair (MP12 = L1 multipath using L2 partner; MP21 = L2 multipath using L1 partner). Shiono & Kubo 2025 core baseline.

Figure 7: Multipath RMS distributions — L1/L5 pair (MP15 = L1 multipath using L5 partner; MP51 = L5 multipath using L1 partner). Core baseline.

Figure 8: Reference multipath RMS distributions — L1/Galileo E5b pair (MP17/MP71). Larger numerical scale due to the L1/E5b frequency-pair coefficient. Not part of the absolute-qualification baseline (E5b exhibited too much site-to-site variance to function as a qualification metric in Shiono & Kubo 2025).

5.2.3 Cycle slips

Figure 9: Station-monthly cycle slips (ION + core MP-combination slips, summed across the elmask-15 elevation bins). Paper-aligned definition (Shiono & Kubo 2025 Table 1). Logarithmic binning.

5.3 Spatial Distribution

The maps below aggregate the 1,298 station-monthly values into a national hex grid: each hexagon is ~60 km flat-to-flat and is coloured by the median of the station-monthly values of the stations falling inside it. The grid is drawn on an Albers Equal-Area projection so every cell covers the same ground area, making colour directly comparable across the country and between months. Cells backed by fewer than 3 reporting stations are drawn with a dotted inner ring — a reliability marking: their median is statistically thin, so read those cells as indicative rather than representative (methodology §5.3, 2026-07-18 revision).

5.3.1 Signal-to-noise ratio

Figure 10: Station-monthly SNR — L1 C/A and L5 (core baseline). Signal-specific colour scales.

Figure 11: Station-monthly SNR — L2 (core) and Galileo E5b (reference; not part of the absolute-qualification baseline). Signal-specific colour scales.

5.3.2 Multipath

Figure 12: Station-monthly multipath RMS — L1/L2 standard pair (MP12 = L1 multipath using L2 partner; MP21 = L2 multipath using L1 partner).

Figure 13: Station-monthly multipath RMS — L1/L5 pair (MP15 = L1 multipath using L5 partner; MP51 = L5 multipath using L1 partner). MP51 typically lower than MP12 — modern L5 signals see less multipath at GEONET sites.

Figure 14: Reference multipath — L1/Galileo E5b pair (MP17/MP71). Larger numerical scale due to the L1/E5b frequency-pair coefficient. Shown for monitoring; not part of the absolute-qualification baseline.

5.3.3 Cycle slips

Figure 15: Core cycle slips per station-day (ION + MP12/21/15/51 slips, elmask-15, daily mean over month). Paper-aligned definition. Logarithmic colour scale.

Note

Per free-tier scope, only the hex-aggregated (per-cell median) values are shown — individual station identifiers and per-station values are reserved for the Pro-tier report. Color scales are fixed per signal (see the Appendix glossary) so successive months can be compared at a glance.

5.4 Receiver / Antenna Inventory

Figure 17: Top 10 receiver × antenna combinations across the network.

Top 10 receiver × antenna combinations cover 74.1 % of 1,298 reporting stations; 46 distinct combinations exist in total.

Note

Equipment changes vs. previous month are tracked via aggregated counts only (e.g. “N stations changed receiver, M stations changed antenna”); individual station identities are reserved for the Pro-tier report. Month-over-month deltas will appear once a baseline month is established.

5.5 Absolute Station Qualification

Note

Coming Soon. Absolute station qualification — i.e. classifying each GEONET station as passing or failing the four core QC criteria defined in Shiono & Kubo (2025) — will appear here once the moving-window infrastructure (a rolling 3-month window at daily granularity, n ≈ 91 daily values per station per qualification cycle) is in place. The qualification criterion is the 99.73rd percentile (3σ) of the daily metrics over the rolling 3-month window for each of:

Visibility — Complete obs / Possible obs > 10°
SNR — mean SNR for L1, L2, L5 (SN1, SN2, SN5)
Multipath — RMS of MP12, MP21, MP15, MP51
Cycle slips — cycle_slips_core (ION + MP12/21/15/51 slips)

The rolling-3-month × daily window is a deliberate operational deviation from the published Shiono & Kubo (2025) weekly-over- rolling-year methodology, adopted for operational timeliness (alignment with the recent-3-months reporting cadence), environmental adaptation, and improved statistical robustness (n ≈ 91 vs. 53).

Per the original study, the Galileo E5b family (SN7, MP17, MP71) is intentionally excluded from the qualification set: at the time of the four-year baseline (2021–2024), L1/E5b values exhibited considerably larger site-to-site variance than the L1/L2/L5 pairs, making them unreliable as a pass/fail threshold. They remain in the report as reference / supplementary monitoring.

The output of this section will be a national pass-rate (e.g. “1,055 of 1,298 stations passed all four core criteria”) with aggregate counts only — individual station names are reserved for the Pro-tier report.

6 Appendix

6.1 GNSS System Events: NAGU / NANU / NAQU

Notices issued against GNSS constellation operations during May 2026, recorded for cross-referencing against observation anomalies and signal availability. Sourced from the official NAGU (Galileo, EUSPA/GSC), NANU (GPS, USCG-NAVCEN) and NAQU (QZSS, QSS) notice feeds.

Table 4: GNSS system notices within the reporting period.

Date	Satellite	Notice	Event type	Severity
2026-05-05 12:59 UTC	QZS PRN199	NAQU 2026146, NAQU 2026149	scheduled_maintenance	total
2026-05-08 07:30 UTC	GAL	NAGU 2026030, NAGU 2026031	scheduled_maintenance	informational
2026-05-08 18:00 UTC	GPS PRN27	NANU 2026041, NANU 2026043	scheduled_maintenance	total
2026-05-12 09:29 UTC	GAL	NAGU 2026032	frequency_outage	partial
2026-05-13 05:59 UTC	QZS PRN200	NAQU 2026148, NAQU 2026150	scheduled_maintenance	total
2026-05-19 13:59 UTC	GPS PRN28	NANU 2026042, NANU 2026044	other	total
2026-05-21 10:31 UTC	GAL	NAGU 2026033	other	total
2026-05-21 12:51 UTC	QZS PRN194	NAQU 2026168	unscheduled_outage	partial
2026-05-21 12:53 UTC	QZS PRN194	NAQU 2026153, NAQU 2026166	other	partial
2026-05-21 13:08 UTC	QZS PRN185	NAQU 2026167	unscheduled_outage	partial
2026-05-21 13:08 UTC	QZS PRN204	NAQU 2026162, NAQU 2026165	other	partial
2026-05-21 13:08 UTC	QZS PRN195	NAQU 2026160, NAQU 2026163	other	partial
2026-05-21 13:08 UTC	QZS PRN184	NAQU 2026154, NAQU 2026157	other	partial
2026-05-21 13:08 UTC	QZS PRN184	NAQU 2026156, NAQU 2026158	other	partial
2026-05-21 13:08 UTC	QZS PRN184	NAQU 2026155, NAQU 2026159	other	partial
2026-05-21 13:08 UTC	QZS PRN205	NAQU 2026161, NAQU 2026164	other	partial
2026-05-22 13:00 UTC	QZS PRN204	NAQU 2026171, NAQU 2026173	other	partial
2026-05-22 13:00 UTC	QZS PRN194	NAQU 2026170, NAQU 2026172	other	partial
2026-05-25 14:59 UTC	QZS PRN199	NAQU 2026151, NAQU 2026175	scheduled_maintenance	total
2026-05-29 04:34 UTC	QZS PRN195	NAQU 2026178, NAQU 2026182	other	partial
2026-05-29 04:35 UTC	QZS PRN205	NAQU 2026179, NAQU 2026183	other	partial
2026-05-29 04:36 UTC	QZS PRN200	NAQU 2026177, NAQU 2026181	other	partial
2026-05-29 04:36 UTC	QZS PRN210	NAQU 2026176, NAQU 2026180	other	partial

23 notice(s) detected for May 2026, collected from the official NAGU (Galileo), NANU (GPS) and NAQU (QZSS) feeds.

6.2 List of Earthquakes

Earthquakes during the reporting period for which the Japan Meteorological Agency issued a press release (in practice: maximum seismic intensity 5-lower or greater), listed for interpreting GEONET observation anomalies. Aftershocks folded into a mainshock’s series are shown under it. Source: JMA website (edited); origin times are JST.

Earthquakes with a JMA press release, May 2026 (2 rows). Source: JMA website.
Origin (JST)	Epicentral region	M	Depth (km)	Max. int.	JMA name	Press release
05-15 20:22	宮城県沖	6.4	46	5弱		JMA
05-20 11:46	沖縄本島近海	5.9	50	5強		JMA

6.3 List of Satellites

A snapshot of the constellation operators’ official status pages at fetch time (not a period summary — the operator pages are themselves live snapshots). Sources: GPS = USCG NAVCEN, QZSS = QSS, Galileo = GSC Europa. GLONASS is excluded from this report’s QC pipeline (per methodology); PNT Moni does, however, evaluate the Galileo signals received at GEONET stations.

Fetched at: 2026-06-02 02:42 UTC

6.3.1 GPS

Table 5: GPS satellite constellation status.

PRN	SVN	Block	Slot	Clock	Status	Notice
G01	80	III	D2	RB	Unusable	UNUSABLE
G02	61	IIR	D1	RB	Operational	FCSTSUMM
G03	69	IIF	E1	RB	Operational	FCSTSUMM
G04	74	III	F4	RB	Operational	FCSTDV
G05	50	IIR-M	E3	RB	Operational	FCSTSUMM
G06	67	IIF	D4	RB	Operational	FCSTDV
G07	48	IIR-M	A4	RB	Operational	FCSTSUMM
G08	72	IIF	C3	RB	Operational	FCSTSUMM
G09	68	IIF	F3	RB	Operational	FCSTSUMM
G10	73	IIF	E2	RB	Operational	FCSTSUMM
G11	78	III	D5	RB	Operational	FCSTSUMM
G12	58	IIR-M	B4	RB	Operational	FCSTSUMM
G13	43	IIR	A5	RB	Decommissioned	DECOM
G14	77	III	B6	RB	Operational	FCSTSUMM
G15	55	IIR-M	F2	RB	Operational	FCSTSUMM
G16	56	IIR	B1	RB	Operational	FCSTSUMM
G17	53	IIR-M	C4	RB	Operational	FCSTMX
G18	75	III	D6	RB	Operational	FCSTSUMM
G19	59	IIR	C5	RB	Operational	FCSTSUMM
G20	82	III	F5	RB	Operational	FCSTSUMM
G21	81	III	E6	RB	Operational	FCSTSUMM
G22	44	IIR	B3	RB	Operational	FCSTSUMM
G23	76	III	E5	RB	Operational	FCSTSUMM
G24	65	IIF	A1	RB	Unusable	UNUSABLE
G25	62	IIF	B2	RB	Operational	FCSTSUMM
G26	71	IIF	B5	RB	Operational	FCSTSUMM
G27	66	IIF	C2	RB	Operational	FCSTSUMM
G28	79	III	A6	RB	Unusable	UNUSABLE
G29	57	IIR-M	C1	RB	Operational	FCSTSUMM
G30	64	IIF	A3	RB	Operational	FCSTSUMM
G31	52	IIR-M	A2	RB	Operational	FCSTSUMM
G32	70	IIF	F1	RB	Unusable	UNUSABLE

6.3.2 QZSS (Michibiki)

Table 6: QZSS satellite constellation status.

PRN	SVN	Block	Signals	Status
J194	002	Ⅱ-Q	L1C/A, L1C, L2C, L5, L1S, L5S, L6D, L6E	Operational
J195	004	Ⅱ-Q	L1C/A, L1C, L2C, L5, L1S, L5S, L6D, L6E	Operational
J196	005	ⅡA-Q	L1C, L2C, L5, L1C/B, L1S, L5S, L6D, L6E	Operational
J199	003	Ⅱ-G	L1C/A, L1C, L2C, L5, L1S, L5S, L1Sb, L6D, L6E, Sr/Sf	Operational
J200	007	Ⅲ-G	L1C, L5, L1C/B, L5S, L1Sb, L6D, L6E	Operational

6.3.3 Galileo

Table 7: Galileo satellite constellation status.

E#	GSAT	Clock	Status	Notice
E01	GSAT0210	RAFS	Unusable	GENERAL 2023048
E02	GSAT0211	PHM	Operational
E03	GSAT0212	PHM	Operational
E04	GSAT0213	PHM	Operational
E05	GSAT0214	PHM	Operational
E06	GSAT0227	PHM	Operational
E07	GSAT0207	PHM	Operational
E08	GSAT0208	PHM	Operational
E09	GSAT0209	RAFS	Operational
E10	GSAT0224	PHM	Operational
E11	GSAT0101	RAFS	Operational
E12	GSAT0102	RAFS	Operational
E13	GSAT0220	PHM	Operational
E14	GSAT0202	RAFS	Unusable	GENERAL 2021008
E15	GSAT0221	PHM	Operational
E16	GSAT0232	PHM	Operational
E18	GSAT0201	PHM	Unusable	GENERAL 2021008
E19	GSAT0103	RAFS	Operational
E21	GSAT0215	PHM	Operational
E22	GSAT0204	RAFS	Unusable	GENERAL 2017045
E23	GSAT0226	PHM	Operational
E25	GSAT0216	PHM	Operational
E26	GSAT0203	PHM	Operational
E27	GSAT0217	PHM	Operational
E28	GSAT0233	PHM	Operational	USABINIT 2026033
E29	GSAT0225	PHM	Operational
E30	GSAT0206	PHM	Operational
E31	GSAT0218	PHM	Operational
E32	GSAT0234		Commissioning	LAUNCH 2025061
E33	GSAT0222	PHM	Operational
E34	GSAT0223	PHM	Operational
E36	GSAT0219	PHM	Operational

Reproducibility. This report is generated by the open-source pntmoni-pipeline toolchain from the publicly available GEONET archive. Methodology 1.2.0 · QC tool teqc 2019Feb25 · convbin RTKLIB 2.4.2 — versioned alongside the report.

6.4 Metric Glossary

Symbol-by-symbol definitions of the metrics used throughout this report, as established in Shiono & Kubo (2025, 2026). The full methodology document is [https://pntmoni.com/methodology/qc/v1.2.0](https://pntmoni.com/methodology/qc/v1.2.0).

6.4.1 Core metrics (absolute-evaluation baseline)

These are the four families used in the paper’s Table 1 station selection and are the basis for the planned absolute station qualification (see §5.6).

Metric	Symbol	Description
Data availability	`data_availability`	`epochs_w_obs / expected_epochs` — fraction of the day’s 2,880 nominal 30-second epochs where the station logged at least one observation. Measures whether the station was up and recording.
Visibility (可視率)	`visibility`	`Complete obs >10° / Possible obs >10°` — fraction of expected satellite-epoch tracks above teqc’s 10° elevation mask that were actually obtained. Measures track completeness when the station was operating: low values indicate antenna obstructions, RF interference, or receiver issues even on a station that logs data every epoch.
L1 C/A SNR	`SN1`	Mean signal-to-noise ratio on L1 C/A, in dB-Hz.
L2 SNR	`SN2`	Mean signal-to-noise ratio on L2 (P-code or L2C), in dB-Hz.
L5 SNR	`SN5`	Mean signal-to-noise ratio on L5, in dB-Hz.
Multipath (L1, L2 partner)	`MP12`	RMS of the L1 multipath combination using L2 as partner, in metres.
Multipath (L2, L1 partner)	`MP21`	RMS of the L2 multipath combination using L1 as partner, in metres.
Multipath (L1, L5 partner)	`MP15`	RMS of the L1 multipath combination using L5 as partner, in metres.
Multipath (L5, L1 partner)	`MP51`	RMS of the L5 multipath combination using L1 as partner, in metres.
Cycle slips (core)	`cycle_slips_core`	Sum of teqc-reported ION slips and the four core MP-combination slips (`MP12 + MP21 + MP15 + MP51`). Paper-aligned definition.

6.4.2 Reference / supplementary monitoring (Galileo E5b)

These are reported as informational reference. They are not part of the absolute-qualification baseline because the L1/E5b frequency pair exhibits considerably larger site-to-site variance than the L1/L2/L5 pairs and was therefore not adopted as a qualification metric in Shiono & Kubo (2025).

Metric	Symbol	Description
Galileo E5b SNR	`SN7`	Mean signal-to-noise ratio on E5b (1207.140 MHz), in dB-Hz.
Multipath (L1, E5b partner)	`MP17`	RMS of the L1 multipath combination using E5b as partner, in metres. The `2/(α-1)` coefficient in the multipath formula is large for the L1/E5b frequency pair, hence the larger numerical values.
Multipath (E5b, L1 partner)	`MP71`	RMS of the E5b multipath combination using L1 as partner, in metres.
Cycle slips (extended)	`cycle_slips_extended`	`cycle_slips_core` plus `MP17` and `MP71` slips. Useful when assessing receivers that track Galileo E5b; not used in qualification.

Sources & terms of use: GEONET data is distributed by GSI under PDL 1.0 (source: GSI GEONET data service). Satellite operational notices are sourced from the official feeds (GPS = USCG NAVCEN, QZSS = QSS, Galileo = GSC Europa).