Methodology

Our methods depend on the question. Publisher documentation can establish what a source says it offers. A command run can establish what one software version did with one input. A browser check can establish how one of our tools behaved in a named configuration. None of those, alone, proves the others.

Source and product compilations

For the public-data source list and the elevation product table, we read each publisher’s own documentation and record coverage, formats, access route, account requirements, reference systems, stated accuracy and terms, with the date checked and a link to the source. Short quotations are kept in each asset’s source ledger. A field the documentation does not establish is recorded as unknown rather than filled with a typical value. These are documentation records: we did not download every product or measure its accuracy.

Round-trip observations

Format observations use small original fixtures with known values. Each run records the software and version, the configuration (for example an explicit or an inferred schema), the input, the output and the comparison rule. Field definitions, stored values, projected properties and coordinates are compared separately, so a renamed field, a converted value and a key collision are not reduced to one score. Results describe the tested configuration, not every option of a tool or every file.

Commands and examples

A command shown on a page is run as printed in a named environment with the software version recorded, unless the page states that it was not run. Inputs are identified by publisher, product and identifier. Outputs are checked against their inputs rather than judged by appearance.

Tools

The data finder filters a static table in your browser. It does not search the web, contact a publisher or download anything. Its filters and counts were checked in a real browser and the observation is published with the data.

What we publish

Compilations and observations are CC BY 4.0, and original code is MIT licensed. Each asset’s METHOD file, hash list and source ledger are published with it. Those licences do not relicense third-party data, documentation or software.