Cataster measures ambient noise using the device microphone, tags each reading with location and time, and plots them on a shared map backed by Supabase. Built with Expo, React Native and TypeScript. Full source code, a setup guide and the Supabase SQL schema are included. What is not included — please read The dBFS-to-SPL conversion uses a fixed offset. Microphone sensitivity varies by device by roughly ±15 dB, so the absolute values are not calibrated — they are useful as relative comparisons, not as measurements you could cite. If you ship this, add a per-device calibration flow and label readings accordingly. That is a real piece of work, and the price reflects that it is missing. The UI text is German and there is no i18n layer. No in-app purchases. Sold as-is. No support, updates or customization included.