Add fe-map and iss sources, The Shape of Distance as published, contribution guide

- femap/: planar best-effort solver, build, result and page (fe-map.aethercosmology.com)
- satellites/: The Sync Test build, ISS elements, SatNOGS timings and page (iss.aethercosmology.com)
- src/handoff/The_Shape_of_Distance_PRESENTATION.html: inputs for both
- CONTRIBUTING.md; README and LICENSE-DATA cover all four sites; GitHub mirror for issues and pull requests

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

CONTRIBUTING.md

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+# Contributing
+
+Corrections, new measurements and independent re-analyses are welcome,
+including ones that disagree with the results. Every figure on pingstats,
+fe-map and iss is rebuilt from this repository, so a change accepted here
+changes the published numbers. The Shape of Distance is included as published.
+
+Issues and pull requests: https://github.com/aetherbird/cable-latency-survey
+(a mirror of https://git.aethercosmology.com/toby/cable-latency-survey with the same history).
+
+## Report a problem
+
+Open an issue that names the page, the pair or value, what you believe is
+wrong, and the evidence (a source, a log, a measurement ID). Typical cases: a
+server or probe listed in the wrong city, a flight time that does not match its
+track log, a cable length that differs from its published figure, or a step in
+a method that you think biases the result.
+
+## Add measurements
+
+Measurements that anyone can re-fetch are the most useful. Include the raw
+output, not only a summary.
+
+| Kind | What to send |
+|---|---|
+| Ping or traceroute | A RIPE Atlas or Globalping measurement ID; or the raw output of `ping -c 20` and `mtr -rwc 20` with the UTC time, the target, and the source city (a public anchor, a hosted server, or your city to within 25 km). |
+| Flight | Flight number and date for both directions, the track log URL (FlightAware or another ADS-B record), and the aircraft type. |
+| Rail or road | The route and its published length, with the source. |
+| Satellite pass | SatNOGS observation IDs, or raw recordings with station location and UTC timestamps. |
+
+Routes in the southern hemisphere are the most informative: South America to
+Africa and Australia, Africa to Australia, and New Zealand to anywhere.
+
+Do not post your home IP address or street address. A city is enough.
+
+## Change the analysis
+
+Fork the repository, make the change, run the build of the page it affects and
+the browser checks, and open a pull request that states how the published
+numbers change.
+
+| Site | Source | Build |
+|---|---|---|
+| pingstats.aethercosmology.com | `src/` | `cd src && python3 build.py` |
+| fe-map.aethercosmology.com | `femap/` | `cd femap && python3 build.py` (about 10 minutes) |
+| iss.aethercosmology.com | `satellites/` | `cd satellites && python3 build.py` |
+| distance.aethercosmology.com | `src/handoff/The_Shape_of_Distance_PRESENTATION.html` | single published file |
+
+Browser checks: `cd tests && npm install && CH=/path/to/chromium ./run.sh`.
+
+## Rules applied to every contribution
+
+- Each value traces to a public source, a measurement ID, or a raw log in this
+  repository.
+- A measurement is not removed for disagreeing with a model. Cleaning rules,
+  such as the one for mislocated servers, are stated in each page's method
+  section and apply to every measurement alike.
+- Code is contributed under the MIT licence (`LICENSE`); data under CC BY 4.0
+  (`LICENSE-DATA.md`).