IGS Site Log and GeodesyML Guide: 14 Standard Sections, DOMES Syntax, and Station Integrity
An IGS Site Log is the international standard record of a permanent GNSS station instrumentation, monumentation, local ties, and operational history. Automated validation parses all 14 standard sections, verifies 9-character DOMES numbers, checks chronological continuity of receiver and antenna changes, aligns antenna radomes with ANTEX models, and validates GeodesyML v0.4 and v0.5 XML schemas.
Why station metadata integrity governs precision positioning
In high-precision geodetic positioning and long-term reference frame maintenance, coordinate solutions are inextricably coupled to instrument metadata. A reference receiver recording multi-frequency observations cannot produce rigorous, repeatable coordinates if the antenna model, radome code, or eccentric monument tie vector is recorded incorrectly. Even minor metadata omissions silently corrupt downstream PPP convergence, baseline double-differencing, and global crustal motion velocity fields.
- Unmodeled phase center offsets: Entering an incorrect antenna model or omitting its four-character radome code introduces vertical and horizontal phase center errors exceeding 10 centimeters in carrier-phase estimation.
- Undocumented antenna or receiver swaps: Swapping instrumentation without logging precise UTC epochs corrupts time-series trend analysis, creating artificial coordinate jumps that masquerade as tectonic displacements.
- Discrepancies in Antenna Reference Point (ARP) offsets: Failing to distinguish between true vertical height and slant height to monument benchmarks induces direct systematic z-axis positioning biases.
- Incompatible antenna phase center variation (PCV) conventions: Processing engines require exact alignment with IGS ANTEX calibration models (such as igs20.atx) to model elevation- and azimuth-dependent phase variations.
Fonti: IGS: formats and standards
The 14 standard sections of an IGS Site Log
The International GNSS Service specifies an ASCII-based 14-section format to document the complete operational, physical, and geophysical history of continuously operating reference stations (CORS). Every station log must conform to these numbered sections in exact sequence:
| Section | Standard Section Title | Primary Metadata Attributes | Critical Geodetic Impact |
|---|---|---|---|
| 1 | Site Identification of the GNSS Monument | Site name, 4-char ID, 9-char DOMES number, CDP number, monument description | Defines global geodetic identity and permanent monument integrity |
| 2 | Site Location Information | City, state/province, country, tectonic plate, approx XYZ and geodetic lat/lon/height | Establishes initial spatial clustering and tectonic velocity plate reference |
| 3 | GNSS Receiver Information | Receiver type, serial number, firmware version, tracking satellites, elevation cutoff | Tracks firmware transitions, tracking capabilities, and signal processing biases |
| 4 | GNSS Antenna Information | Antenna type, radome type, serial number, ARP marker, eccentricity dN/dE/dU | Controls phase center offset (PCO) and variation (PCV) model pairing with ANTEX |
| 5 | Local Episodic Effects | Seismic events, volcanic unrest, tree growth, construction activity | Documents transient physical phenomena causing sudden coordinate discontinuities |
| 6 | Local Site Ties | Tied markers, local baseline components (dX, dY, dZ), survey method | Links GNSS monument to co-located VLBI, SLR, or DORIS geodetic techniques |
| 7 | Frequency Standard | Standard type (internal, cesium, rubidium, H-maser), frequency input | Assesses receiver clock stability and PPP clock parameter estimation constraints |
| 8 | Collocation with Other Instrumentation | DORIS, SLR, VLBI, tide gauge, absolute gravimeter | Underpins multi-technique ITRF realization and terrestrial datum unification |
| 9 | Meteorological Instrumentation | Barometer, psychrometer, thermometer, rain gauge, sensor height | Supplies in-situ surface pressure and temperature for tropospheric modeling |
| 10 | Local Ongoing Conditions | Radio frequency interference, multipath environment, geological setting | Flags persistent local noise sources impairing continuous satellite tracking |
| 11 | Local Episodic Effects (Additional) | Secondary environmental shifts, localized snow or icing events | Provides auxiliary qualitative context for transient data quality degradations |
| 12 | Site Log Submitter and Maintenance Agency | Agency name, primary contacts, postal address, email, telephone | Enables data center notification workflows during station outages or discrepancies |
| 13 | Site Log Responsible Agency | Operating agency, on-site contact, network affiliation | Specifies long-term institutional governance and operational custodianship |
| 14 | Log Revision History | Date prepared, report type (NEW/UPDATE), modified section numbers | Tracks administrative provenance and version continuity across updates |
Fonti: IGS: formats and standards
DOMES number syntax and assignment conventions
A DOMES (Directory of MERIT Sites) number is an unambiguous 9-character alphanumeric identifier assigned by the IERS/IGN Central Bureau to identify permanent geodetic tracking monuments. It eliminates nomenclature conflicts when multiple monuments or antennas exist within the same operational facility.
- Five-digit Area Code (Positions 1-5): Identifies the geographical region, country, or municipality where the station is located (e.g., 20801 for Onsala, Sweden, or 40101 for Tsukuba, Japan).
- Single-letter Monument Code (Position 6): Represents the physical type of benchmark. By convention, "M" denotes an observation monument or concrete pillar, while "S" designates an instrument pillar or mobile structure.
- Three-digit Point Identifier (Positions 7-9): Uniquely numbers individual monuments within the area code (e.g., 001, 002). Even if a receiver or antenna is replaced, the monument DOMES number remains unchanged as long as the physical bedrock pillar is preserved.
- Relationship with 9-character Station ID: Modern RINEX 3 and GeodesyML standards combine the 4-character station code, monument number (0-9), receiver number (0-9), and 3-character ISO country code (e.g., ONSA00SWE) to maintain global cross-referencing.
Fonti: IERS / IGN: DOMES station numbering · IGS: formats and standards
GeodesyML XML: Modern digital exchange standard
While legacy IGS site logs rely on fixed-width ASCII formatting, modern geodetic infrastructure increasingly relies on GeodesyML. Developed by Geoscience Australia in collaboration with the IGS, GeodesyML is an open GML-based XML application schema specifically designed for automated transmission, validation, and machine-to-machine exchange of geodetic site metadata.
- Schema validation against XML Schema Definitions (XSD): GeodesyML v0.4 and v0.5 strictly validate ISO datetimes, enumerated receiver/antenna models, and numeric coordinate structures before database ingestion.
- Rich sensor and instrument telemetry: Provides structured XML elements for multi-technique metadata, including meteorological sensor calibrations, antenna cable lengths, and local tie vectors with formal covariance matrices.
- Bidirectional conversion: PosFlow and international data centers automatically parse legacy ASCII .log files into GeodesyML XML documents and serialize GeodesyML back into canonical ASCII logs without information loss.
- Automated API distribution: Facilitates web service integration across global data centers (CDDIS, IGN, SOPAC, GA), enabling real-time metadata synchronizations.
Fonti: GeodesyML: GML standard for geodetic data · IGS: formats and standards
Automated geodetic diagnostic checks for site logs
To maintain network data integrity, PosFlow Site Log Inspector executes rigorous automated diagnostics on uploaded site logs and GeodesyML records. Detecting and flagging discrepancies before submitting logs to regional or global data centers prevents network rejections and flawed baseline solutions.
- DOMES format validation: Verifies that the DOMES string matches the strict ^[0-9]{5}[MS][0-9]{3}$ regular expression syntax.
- Chronological continuity and overlap detection: Validates that consecutive receiver and antenna installations have valid ISO 8601 timestamps without chronologically overlapping operational periods or unclosed historical intervals.
- ANTEX model and radome pairing: Confirms that antenna models match the 20-character IGS naming convention (16-char antenna model + 4-char radome code) present in the active igs20.atx calibration database.
- Spatial coordinate consistency checks: Converts Section 2 Cartesian coordinates (X, Y, Z) to ellipsoidal latitude, longitude, and ellipsoidal height to verify geometric congruence within 50 meters.
- Local tie vector closure: Checks that Section 6 local tie 3D vectors between adjacent monuments maintain internal closure and consistent coordinate frame definitions.
Fonti: IGS: formats and standards · GeodesyML: GML standard for geodetic data
Audit and manage site logs in PosFlow
PosFlow provides browser-based and programmatic tools to inspect, validate, and manage permanent GNSS station metadata alongside RINEX observation data.
- Online Site Log Inspector: Drag and drop any ASCII IGS site log or GeodesyML XML file into /site-log-inspector to instantly view parsed 14 sections, DOMES integrity checks, and chronological equipment timelines.
- Automated antenna and RINEX header cross-auditing: Upload RINEX observation files alongside site logs to verify that RINEX header antenna types, receiver types, and antenna heights match the official log.
- Continuous CORS quality tracking: Combine station log validation with automated multi-frequency RINEX quality analysis to monitor reference station performance over multi-year horizons.
- Standard export: Download validated GeodesyML XML files or formatted canonical ASCII logs ready for submission to IGS and EUREF data centers.
Fonti: IGS: formats and standards
Domande frequenti
What is an IGS Site Log and who maintains it?
An IGS Site Log is the standardized metadata document describing the physical, environmental, and operational history of a permanent GNSS tracking station. It is prepared by the station operating agency and submitted to international data centers (such as CDDIS, IGN, or regional densifications like EUREF) under the coordination of the International GNSS Service.
What does a 9-character DOMES number represent?
Assigned by the IERS / IGN Central Bureau, a DOMES number consists of a 5-digit geographical area code, a single letter denoting monument type ("M" for permanent monument, "S" for instrument pillar), and a 3-digit point sequence number (e.g., 20801M001). It ensures permanent, globally unique identification for geodetic tracking monuments.
What is the advantage of GeodesyML over legacy ASCII site logs?
GeodesyML is an XML/GML standard that enforces strict schema validation (XSD), machine readability, structured multi-technique ties, and automated web-service exchange. It eliminates parsing ambiguities and character-spacing errors common in legacy ASCII site logs while enabling automated API synchronization across global data centers.
How can I validate an IGS site log before submitting to data centers?
You can upload your ASCII site log or GeodesyML XML file directly to PosFlow Site Log Inspector (/site-log-inspector). The tool parses all 14 standard sections, verifies DOMES syntax, validates chronological equipment continuity, and confirms antenna model compatibility with IGS ANTEX calibrations.
Riferimenti e metodologia
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