5 Common Coordinate Mistakes That Misplace Map Markers in Developer Projects

Developers frequently encounter misplaced map markers due to avoidable coordinate errors, according to a debugging guide published on DEV Community. One of the most common issues is passing latitude and longitude in the wrong order, since APIs like MapLibre GL JS and GeoJSON expect longitude first, unlike the browser Geolocation API. Coordinates from projected systems such as Web Mercator (EPSG:3857) must be transformed before use, as their metre-based values cannot be passed directly to functions expecting decimal degrees. Degrees-minutes-seconds (DMS) format must also be properly converted to decimal degrees, since JavaScript's parseFloat will silently truncate such strings and return misleading values. The guide recommends inspecting raw input values, confirming the coordinate reference system of every data source, and consulting API documentation rather than assuming coordinate order from UI labels.