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WGS84 and Web Mercator

EPSG:4326 stores geographic longitude/latitude coordinates in degrees. EPSG:3857 is the Web Mercator projection used by most global web-map tile systems.

They are not interchangeable.

EPSG:4326​

Use for:

  • KML/Google Earth exchange
  • many GPS/API coordinate inputs
  • global longitude/latitude datasets

Degree differences are not constant metre distances.

EPSG:3857​

Use for:

  • displaying standard global web tiles
  • interoperating with web-map basemaps

Do not use Web Mercator as the calculation CRS for precise New Zealand area/distance work; scale distortion increases away from the equator.

Desktop pattern​

Keep a QGIS project in EPSG:2193 and let QGIS reproject EPSG:3857 basemap tiles on the fly. Export KML to EPSG:4326 as part of the output workflow.

Last reviewed: 26 August 2026

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