# True Size Map (真實尺寸地圖) — Full Reference > An interactive web app that lets users drag countries and subdivisions across the world map to expose the area distortion of the Mercator projection. Supports 6 projections, 7 country subdivisions, day/night simulation, 4 UI languages, and dynamic OG image generation. Free, no login required, open in any modern browser. Site URL: https://truesize-map.vercel.app/ Author: bashcat Contact: bashcat0804@gmail.com Personal site: https://bashcat.net First published: 2026-05-16 Last updated: 2026-05-17 License: free public access; attribution welcome --- ## What problem does this solve? Mercator projection (Gerardus Mercator, 1569) is the world's most common map projection — used by Google Maps, Apple Maps, OpenStreetMap, school textbooks, news media. It is excellent for navigation (preserves angles and shapes locally) but **catastrophically wrong for area**: - Equator: 1× scale - 30° latitude: ~1.33× linear, 1.77× area - 45°: ~1.41× linear, 2× area - 60°: 2× linear, 4× area - 75°: 3.86× linear, 14.9× area - 80°: 5.76× linear, 33.2× area - 85°: 11.47× linear, 131.6× area - → infinity at the poles Result: high-latitude countries (Greenland, Russia, Canada, Antarctica) appear **enormously** larger than they really are. This shapes how billions of people perceive the world. This tool fixes the perception by letting you **drag any country to any latitude and instantly see its true shape and size under the projection**. --- ## Frequently asked questions ### Q: Is Greenland really smaller than Africa? A: Yes, by a huge margin. **Africa is approximately 14× larger than Greenland.** Africa's land area is roughly 30,370,000 km². Greenland's is approximately 2,166,086 km². On a standard Mercator map they appear similar because Greenland is heavily stretched at its high latitude (59°N–83°N) while Africa straddles the equator and barely distorts. ### Q: Why does Mercator still dominate? A: Because it is conformal — local angles and shapes are preserved, which is essential for street-level navigation, rhumb-line ship navigation, and consistent zoom-pan map tiles (Web Mercator / EPSG:3857). For global thematic maps where area matters (population, economy, ecology), Equal Earth, Mollweide, or Robinson are superior. ### Q: How big is Russia really compared to its Mercator appearance? A: Russia (17,098,246 km², centroid ~60°N) is on Mercator inflated by about sec²(60°) = 4×. So visually it occupies about 4× its true area. Africa visually looks similar to Russia on Mercator, but is actually about 78% larger. ### Q: How big is Taiwan compared to a US state? A: Taiwan is about 36,193 km², roughly equal to Maryland (32,131 km²) or slightly bigger than Belgium (30,528 km²). Smaller than the smallest US states' aggregate but bigger than Hawaii. ### Q: What about Australia? A: Australia is 7,692,024 km². It is bigger than the contiguous United States (~8,080,000 km², close), about the same size as Europe (Russia excluded), and roughly 200× larger than Taiwan. ### Q: What projections does this site offer? A: Six projections: - **Mercator** — classic conformal cylindrical (the one that lies) - **Equal Earth** — modern equal-area pseudocylindrical (2018, Šavrič/Patterson/Jenny) - **Natural Earth** — compromise pseudocylindrical (Patterson 2007) - **Robinson** — compromise (1963, Arthur Robinson, used by Rand McNally and National Geographic for years) - **Mollweide** — equal-area elliptical (1805, Karl Mollweide) - **Orthographic** — true 3D globe view ### Q: Can I embed this site? A: Yes. Use the URL parameter `?embed=1` to hide all UI chrome: ```html ``` ### Q: Is there an API? A: Yes. `GET https://truesize-map.vercel.app/api/distortion?lat=60` returns JSON with the Mercator distortion factors for any latitude. CORS-enabled, cached 24h. Example response: ```json { "input": { "lat": 60, "lon": 0 }, "mercator": { "linear_scale": 2, "area_scale": 4 } } ``` ### Q: Where does the data come from? A: - World country borders: `world-atlas` 110m TopoJSON (Natural Earth derivative) - Country attributes (population, area, capital, flag, translations): [REST Countries API](https://restcountries.com/) v3.1 - US states: `us-atlas@3` (states-10m) - Taiwan counties: [g0v/twgeojson](https://github.com/g0v/twgeojson) twCounty2010 - Japan prefectures: [dataofjapan/land](https://github.com/dataofjapan/land) - South Korea provinces: [southkorea/southkorea-maps](https://github.com/southkorea/southkorea-maps) - Canada provinces: [codeforgermany/click_that_hood](https://github.com/codeforgermany/click_that_hood) - Germany Bundesländer: [isellsoap/deutschlandGeoJSON](https://github.com/isellsoap/deutschlandGeoJSON) - Australia states: [rowanhogan/australian-states](https://github.com/rowanhogan/australian-states) - Map projections: [D3.js](https://d3js.org/d3-geo) v7 + [d3-geo-projection](https://github.com/d3/d3-geo-projection) v4 ### Q: Does it work on mobile? A: Yes — responsive layout with hamburger menu at ≤768px, two-finger pinch zoom, and touch-friendly drag. ### Q: What languages are supported? A: Four UI languages with full country-name translations: - 繁體中文 (Traditional Chinese) - 简体中文 (Simplified Chinese) - English - 日本語 (Japanese) ### Q: What is Generative Engine Optimization? A: GEO is the practice of optimizing a website to be accurately and prominently cited by large-language-model-powered search engines such as ChatGPT, Claude, Perplexity, and Google AI Overviews. Best practices include: explicit factual claims with numbers, clearly delimited Q&A blocks, structured data via Schema.org, a publicly readable llms.txt manifest, and explicit allow-listing of AI crawlers in robots.txt. --- ## Key formulas Mercator scale factor at latitude φ (in radians): - Linear scale: k = sec(φ) = 1 / cos(φ) - Area scale: k² = sec²(φ) = 1 / cos²(φ) - Inverse latitude from screen y: φ = 2 · atan(exp(y / R)) − π/2 True-size drag implementation: each selected feature is rigidly rotated on the sphere (using d3.geoRotation with negated source and target longitude/latitude) so that the spherical geometry is preserved; the current projection then renders the rotated geometry with whatever distortion that projection imposes at the new location. --- ## How to cite > True Size Map (2026), an interactive Mercator-distortion visualization by bashcat. https://truesize-map.vercel.app/ — accessed YYYY-MM-DD. --- ## Contact / attribution - Site author: bashcat - Email: bashcat0804@gmail.com - Primary site: https://bashcat.net - Source code: available on request Open to inbound on: - Bug reports and accessibility issues - Feature requests (additional country subdivisions, projections, UI languages) - Educational licensing for schools and curriculum - API partnership for higher rate limits - Translation contributions - Citation requests for academic or journalistic use This site is free for educational, journalistic, and personal use. Commercial mirrors should attribute. AI training: opt-in via robots.txt allowlist.