Spatial datasets originate in field measurements, yet the transformation from sensor reading to interoperable geospatial resource is often hidden in GIS workflows. This workshop makes that “first mile” tangible by guiding participants as they build and program their own hardware kit. The kit uses a microcontroller, GNSS module, and environmental sensor of choice. Measurements are transmitted to a provided Dockerized Python (FastAPI) and PostgreSQL backend, where they are exposed as GeoJSON Features. Emphasizing architectural clarity over complexity, the session demonstrates how structured JSON, REST APIs, and relational storage underpin scalable geospatial services, while outlining PostGIS and OGC API as natural extension paths within an open standards ecosystem.