Coordinates on a map are a pair of numbers that pinpoint any location on Earth. The system works like a grid: one number (latitude) tells you how far north or south a place is, and the other (longitude) tells you how far east or west it is. Together, these two numbers can identify a spot as broad as a city or as precise as a park bench.
How Latitude and Longitude Work
The coordinate system treats Earth as a sphere divided by two sets of imaginary lines. Latitude lines run horizontally, parallel to each other, like the rungs of a ladder. Longitude lines run vertically from the North Pole to the South Pole, converging at the top and bottom like the segments of an orange.
Latitude is measured from the Equator, which sits at 0 degrees. Values range from 0° at the Equator to 90° at the North Pole and -90° (or 90° South) at the South Pole. If you’re anywhere in the Northern Hemisphere, your latitude is a positive number. Southern Hemisphere locations get a negative number.
Longitude is measured from the Prime Meridian, a line that runs through the Royal Observatory in Greenwich, England, set at 0 degrees. From there, values go up to 180° East and 180° West, meeting at the antimeridian on the opposite side of the globe in the Pacific Ocean. Eastern Hemisphere locations are positive, western ones are negative. That means New York City, which sits west of Greenwich, has a negative longitude, while Tokyo, which sits east, has a positive one.
Reading a Coordinate Pair
The standard convention is to list latitude first, then longitude. A coordinate pair for a location in Hawaii might look like this: 21.3069°, -157.8583°. The first number (positive) tells you the spot is north of the Equator. The second number (negative) tells you it’s west of the Prime Meridian. With just those two numbers, you’ve identified a single point on the planet.
Cardinal direction letters sometimes replace the positive and negative signs. Instead of writing -157.8583°, you might see 157.8583° W. Both formats mean the same thing:
- Positive latitude = North
- Negative latitude = South
- Positive longitude = East
- Negative longitude = West
Degrees, Minutes, and Seconds vs. Decimal Degrees
You’ll run into two common formats for writing coordinates. The older system, Degrees Minutes Seconds (DMS), breaks each degree into 60 minutes, and each minute into 60 seconds, borrowing the same base-60 system the Babylonians used for timekeeping. A DMS coordinate looks like this: 45° 30′ 00″ N, 150° 15′ 00″ W.
The newer format, Decimal Degrees (DD), expresses the same location as a single number with a decimal point: 45.50, -150.25. It’s simpler, easier to type into apps and GPS devices, and has become the default for most digital tools. If you ever need to convert between the two, the formula is straightforward: take the degrees, add the minutes divided by 60, and add the seconds divided by 3,600.
For example, a coordinate of 40° 51′ 59″ converts to 40 + (51/60) + (59/3600) = 40.8664° in decimal form. Most online tools handle this conversion automatically, but it’s useful to know why the numbers look different depending on where you see them.
What Sits Behind the Numbers
Coordinates depend on a reference model of Earth’s shape called a datum. The most widely used datum today is WGS 84 (World Geodetic System 1984), which is the reference system built into GPS satellites and virtually every online mapping service. It models Earth’s size, shape, and gravity field so that a given coordinate pair points to the same physical spot no matter which device or app you’re using. When you see coordinates from Google Maps, a handheld GPS, or an aviation chart, they’re almost certainly based on WGS 84.
Older maps, especially paper topographic maps, sometimes use different datums. A coordinate read from a 1970s USGS map could be off by tens of meters if you plug it into a modern GPS without accounting for the datum difference. This rarely matters for casual use, but it’s worth knowing if you’re doing precise navigation or land surveying.
UTM: The Other Grid System
Not every map uses latitude and longitude. Topographic maps and military maps often use the Universal Transverse Mercator (UTM) system instead. UTM divides the world into 60 north-south zones, each 6 degrees of longitude wide, and measures distances in meters rather than degrees. Instead of a latitude/longitude pair, you get an “easting” (how far east within your zone) and a “northing” (how far north from the Equator).
The advantage of UTM is that it works on a flat grid, which makes measuring straight-line distances and areas much easier than working with curved degree lines. Hikers and surveyors tend to prefer it for fieldwork. The tradeoff is that you need to know which of the 60 zones you’re in for the numbers to make sense, whereas latitude and longitude work everywhere without zone references.
Finding Coordinates in Google Maps
On a desktop browser, right-click any spot on Google Maps and select “What’s here?” A small panel appears at the bottom showing the latitude and longitude in decimal degrees. Click those numbers to copy them.
On the mobile app (iOS or Android), tap and hold any spot on the map until a red pin drops. Swipe up on the info panel at the bottom, and you’ll see the GPS coordinates listed below the address. You can copy them from there to share or save. The coordinates Google Maps gives you are in decimal degrees using the WGS 84 datum, so they’ll work directly in any other modern mapping tool or GPS device.
Practical Tips for Using Coordinates
When sharing coordinates with someone, always include both numbers and specify the format. Sending “45.50, -150.25” is clear. Sending just “45.50” is not, because without the longitude, the number could refer to any point along an entire horizontal band circling the globe.
Precision matters too. Each decimal place in a coordinate adds roughly a tenfold increase in accuracy. One decimal place (45.5°) gets you within about 11 kilometers. Four decimal places (45.5000°) narrow it to about 11 meters. Six decimal places pin a location to within roughly 11 centimeters. For meeting a friend at a restaurant, three or four decimal places are plenty. For surveying property lines, you’d want six or more.
If you’re entering coordinates into a search bar or GPS device, double-check the sign. Swapping a positive longitude for a negative one can place you on the wrong side of the planet. A common mistake is entering coordinates for somewhere in North America but forgetting the negative sign on the longitude, which lands you somewhere in Central Asia instead.