IGC competition judging: a referee guide to airspace, cylinders and altitude conflicts

This is a rule-based technical guide, not a field interview or an official federation decision. The event rulebook in force always takes precedence. Variograph can make the review evidence easier to inspect; it does not certify a task or issue an official penalty.

Search targets: primary term IGC competition judging; long-tail terms how to check an IGC airspace infringement and task cylinder validation barometric GPS altitude.

1. Freeze the file and its signature

Record the source, pilot, UTC start and finish, device and file hash. Treat G-record status separately from flight validity: signed, unsigned, unverifiable or invalid. A signature indicates whether the file changed after recording, not whether the task was completed. Read sampling, gaps and spikes in the IGC data quality report and the signature details in IGC signature and G-record verification.

2. Airspace infringement

Freeze the dated OpenAir or equivalent source. For each volume, record the horizontal polygon, lower and upper limits, reference (MSL, AGL or flight level) and the rule tolerance. Classify each B-record as inside, on the tolerance boundary or outside. Compare barometric and GPS altitude separately, verify suspected crossings with adjacent points, and never treat a thick map line as a tolerance. A visual track in the IGC viewer supports the review; the referee verifies the source and authority.

3. Cylinders, start and ESS

Convert the task into a table: start gate, turnpoints, finish cylinder and ESS line. Store each center, radius, sector, time window and altitude rule. A 1-second log resolves a boundary better than a 5-second log, but neither proves the path between samples. Keep the raw file, task definition and tolerance decision together. Do not turn a boundary case into a definite result by rounding.

4. Barometric versus GPS altitude

Barometric altitude follows pressure and QNH; GPS altitude has different vertical error. A difference is not automatically invalid. First identify the channel and reference named by the event rules, then decide whether the difference is a stable offset or a spike. Check the current FAI/CIVL or local federation text with the event referee; this guide makes no official acceptance claim.

5. A 150+ pilot review queue

Separate ingestion from triage. Store pilot, flight ID, time, signature class, quality level and a manual-review flag. Prioritise integrity issues, points near airspace or cylinder boundaries, baro-GPS conflicts and long gaps. These are queue filters, not automatic rejections. The same raw file should reproduce an appeal report.

Use the IGC viewer and advanced analysis as supporting evidence, alongside the rulebook and referee decision.