Methodology: where the numbers come from
The atlas works exclusively with open data. This page explains which source provides which value, how lengths, areas and size tiers are derived, and how the rankings and comparisons on the pages are calculated.
Sources by category
Rivers: the course comes from OpenStreetMap; the name and facts — length, source, mouth, drainage basin, mean discharge and tributaries — come from Wikidata.
Lakes: the outline comes from OpenStreetMap where a matching one exists, otherwise from HydroLAKES (all lakes from 1 km², remote sensing). HydroLAKES provides area and volume; Wikidata provides maximum depth, inflows and outflows.
Mountain ranges: outlines and hierarchy (ranges, subranges) come from the GMBA Mountain Inventory v2; the highest peak and its elevation come from Wikidata.
Countries: borders come from Natural Earth; capital, population, area, currency, official languages and GDP come from Wikidata. Neighbouring countries are computed from the outlines.
Lengths, areas, density
A river’s length is its official length on Wikidata; where there is none, the atlas measures the course from the OpenStreetMap geometry. If the official length differs strongly from the measured one, the Wikidata value is still shown — with a ⚠ and a link to the statement. Sources are never silently overwritten.
Lengths always refer to the whole river. When a country page says “The longest river in Germany is the Danube (2,850 km)”, that is the total length, not the section within the country.
Population density is population divided by area. Figures with a reference date (population, GDP) carry the year of the value.
Size tiers
Rivers count as “large” from 300 km (official length, otherwise measured). Lakes count as “large” from 100 km² or when they have an article in at least 25 Wikipedia language editions. For mountains, a curated GMBA selection of around 300 ranges forms the large entries, with mountain systems above and subranges below. Countries are covered completely.
Large entries drive the rankings and the country and continent pages. Smaller entries also have their own page with a map and facts and appear in the lists as you scroll.
Rankings and comparisons
Sentences like “the second-longest river in Germany” rest on a ranking across all mapped entries, not only the large ones. Cross-border rivers, lakes and mountain ranges count for each of their countries. Canals do not count as rivers; for mountains, only standalone ranges are ranked, not subranges within a larger one. Named river sections such as the White Nile or the Solimões have their own page, but on the map they are part of the main river and they are not ranked as separate rivers.
Values marked ⚠ and river lengths more than three times the measured length are excluded from every ranking statement — both for the entry itself and for those that would rank behind it.
For sparsely recorded values (maximum depth, discharge, drainage basin) the atlas only mentions top positions, and on country pages only when at least four in five listed entries have a value.
Freshness and data status
The atlas works with snapshots of its sources, not a live connection. River courses come from Geofabrik’s OpenStreetMap extracts, downloaded per region; lake outlines come from QLever’s OSM planet index; facts come from Wikidata. The atlas currently contains data as of:
- River courses · OpenStreetMap, Geofabrik extracts
Russia, Central America, Africa, Asia, South America, Australia/Oceania, Turkey, Cyprus: 18 October 2026; North America: 17 October 2026; Europe: 13 October 2026 - Lake outlines · OpenStreetMap via QLever (OSM planet)
queried on 13 October 2026, planet file of 21 September 2026 - Facts · Wikidata
queried on 19 October 2026
Corrections on Wikidata or OpenStreetMap therefore do not appear immediately but with the next data update. Wikidata facts are refreshed more often than river courses, whose extracts are many gigabytes in size. Every flagged value that disappears afterwards is recorded as an improvement on the “Improve the data” page.
The base map (coastlines, places, roads, boundaries) comes ready-made from OpenFreeMap and follows its own update cycle, usually a few days old.
Found a mistake?
Every item page links straight to the source via “Edit” — facts to Wikidata, courses and outlines to OpenStreetMap. Suspicious values are collected on the Improve the data page. All sources and their licences are listed under Data sources & credits.