Animated transition between Mercator and Equal Earth projections using GPT-6 Astra and D3

The post's author had an animated transition created between the Mercator and Equal Earth map projections out of curiosity. They used the GPT-6 Astra (medium) model in the ChatGPT Work environment and implemented the visualization with the D3.js library. Increased interest in the Equal Earth projection following a vote at the United Nations motivated the work. The demonstration aims to show how to smoothly animate a transition between two projections with different distortion characteristics. Technical details include interpolation of projection parameters and post-processing of map elements with D3. The solution highlights that large language models like GPT-6 Astra can help rapidly prototype frontend geovisualization tasks. The code demonstrates reproducibility and faster development while leaving cartographic quality as an open question. The work can be useful for educational purposes, visual comparisons, and interactive presentations. Related tags: geospatial, d3, vibe-coding and gpt-6-astra.