https://visualizing.jp/en/tags/%E6%95%99%E3%81%88%E3%82%8B%E3%81%9F%E3%82%81%E3%81%AE%E8%A8%98%E4%BA%8B/ Recent content in 教えるための記事 on Visualizing.JP Hugo -- gohugo.io en-US Yuichi Yazaki Wed, 22 Oct 2025 00:00:00 +0900 https://visualizing.jp/en/tissots-indicatrix/ Wed, 22 Oct 2025 00:00:00 +0900 https://visualizing.jp/en/tissots-indicatrix/ <img src="https://visualizing.jp/tissots-indicatrix/images/Tissot_mercator.png" alt="Featured image of post Tissot's Indicatrix" /><p>Every map projection creates distortion because the spherical Earth must be represented on a flat plane. Tissot&rsquo;s indicatrix is a method for showing that distortion quantitatively and visually.</p> <h2 id="basic-principle">Basic Principle </h2><p>French cartographer Nicolas Auguste Tissot introduced the method in 1871. Imagine placing many tiny circles on the globe. When a projection transforms the globe onto a plane, those circles may become ellipses.</p> <p>If a projection were perfectly accurate everywhere, all circles would remain circles. In reality, the size, shape, and orientation of the ellipses reveal how area, angle, and scale are distorted.</p> <h2 id="how-to-read-it">How to Read It </h2><ul> <li>A larger ellipse indicates area enlargement.</li> <li>A smaller ellipse indicates area reduction.</li> <li>An ellipse stretched in one direction indicates directional distortion.</li> <li>A circle suggests local shape preservation.</li> </ul> <h2 id="why-it-matters">Why It Matters </h2><p>Tissot&rsquo;s indicatrix makes projection distortion visible. It helps readers understand that map projections do not merely change appearance; they change measurable properties of geography.</p> <h2 id="summary">Summary </h2><p>Tissot&rsquo;s indicatrix is one of the clearest tools for teaching projection distortion. By turning abstract mathematical distortion into visible ellipses, it helps explain why no flat map can preserve everything.</p> https://visualizing.jp/en/projection-face/ Wed, 22 Oct 2025 00:00:00 +0900 https://visualizing.jp/en/projection-face/ <img src="https://visualizing.jp/projection-face/images/cover.png" alt="Featured image of post Understanding Map Projection Distortion Through Faces: Projection Face" /><p>A map projection transforms the three-dimensional Earth into a two-dimensional map. No projection can preserve distance, area, direction, and shape everywhere at once.</p> <p>Projection Face helps make this unavoidable distortion intuitive by showing how a familiar face changes under different projections. This article connects a classic 1921 cartography example with the modern interactive work &ldquo;Projection Face.&rdquo;</p> <h2 id="from-3d-to-2d">From 3D to 2D </h2><p>The Earth&rsquo;s surface is curved. A flat map is therefore always a transformation, not a perfect copy. Some projections preserve area, others preserve local shape, and others preserve distance or direction from certain points.</p> <h2 id="why-faces-work">Why Faces Work </h2><p>Humans are extremely sensitive to facial distortion. A small change in proportion can feel immediately wrong. By projecting a face instead of only coastlines or graticules, distortion becomes easy to perceive.</p> <h2 id="design-lesson">Design Lesson </h2><p>Projection comparison is often taught with graticules, continents, or Tissot&rsquo;s indicatrix. Faces add another layer: they make distortion emotionally and perceptually obvious.</p> <h2 id="summary">Summary </h2><p>Projection Face is effective because it uses a familiar visual object to explain a technical cartographic problem. It makes map distortion easier to understand by turning it into a change in human appearance.</p>