Opening the Heart of libgd-gis

February 3, 2026

How Ruby Turns Coordinates into Maps (and Why Tests Matter)

Maps look simple on the surface.

You give them coordinates. They give you an image.

But anyone who has gone even slightly deeper knows that coordinates are never just numbers. They are context. They are assumptions. They are projections pretending to be reality.

While working on libgd-gis , I recently spent time opening what I’d call the heart of the library: the place where raw coordinates are normalized, converted, and made safe enough to render as maps — without pretending to be a full GIS system.

This article is about that core: CRS, projections, Mercator, Gauss–Krüger, and why Ruby specs are essential when math starts lying.

libgd-gis

• GitHub Repository
• RubyGems Page

👉 Read the full article.

https://rubystacknews.com/2026/02/03/opening-the-heart-of-libgd-gis/