Coordinates: describing a position on Earth
Learn what latitude and longitude measure, why coordinate order matters, and how a pair of numbers becomes a place software can use.
Why this matters
Maps look visual, but software needs numbers it can compare and exchange. Coordinates give a shared way to describe a position whether the record came from a person, phone, sensor, vehicle, API, or dataset.
Learn it
Latitude measures north or south of the equator. Longitude measures east or west of the Prime Meridian. People often say latitude first, but GeoJSON positions use longitude first, then latitude. The numbers only become fully meaningful when you also know the coordinate reference system; RFC 7946 GeoJSON uses WGS84 longitude and latitude in decimal degrees.
Work through an example
Seattle is often written for people as 47.6062, -122.3321. In a GeoJSON position the same location is [-122.3321, 47.6062]. The values did not change; the order did.
Human: 47.6062, -122.3321
GeoJSON: [-122.3321, 47.6062]Practice
- 1Enter a familiar latitude and longitude in the coordinate exercise.
- 2Flip the order and notice how far the point moves.
- 3Write the same position once for a person and once as a GeoJSON coordinate pair.
Try it
Latitude and longitude
Change the numbers and compare common latitude/longitude order with the longitude/latitude order used by GeoJSON positions.
What to watch for
If two systems disagree about coordinate order, a perfectly valid pair of numbers can land on the wrong side of the world. Always confirm order and reference system before blaming the map.
Where this takes you
This is the starting point for stations, observations, routes, geofences, field data, telemetry, and every later spatial lesson.