GPS coordinates and how to find them in Google Maps

Latitude and longitude: how to read GPS coordinates

The first value is latitude: the angular measure of how far north or south of the Equator a point lies. It is 0° at the Equator and reaches 90° at the poles. Use N and S or signs: positive for north, negative for south. The plus sign can be omitted.

The second value is longitude, the angle between the point’s meridian and the reference meridian at Greenwich. It runs from 0° to 180° east or west: E or a positive value indicates east, W or a negative value indicates west. Greenwich is also a reference for time zones, but coordinates describe a position, rather than a time.

Parallels connect points with the same latitude; meridians connect points with the same longitude. On a spherical model, latitude is the angle between the radius to the point and the equatorial plane. In the geodetic definition used on an ellipsoid, the reference is instead the normal: the direction perpendicular to the ellipsoid’s surface at that point.

For example, 41° 53′ 25.36″ N, 12° 29′ 32.70″ E identifies a point at the Colosseum in Rome. Both values are positive because it lies north of the Equator and east of Greenwich. A large monument occupies many points: the coordinates of an entrance may differ from those of the building’s centre.

DMS, DMM and DD: three formats for the same point

GPS coordinates can be expressed in different notations. These three versions represent the same point at the Colosseum, within the rounding shown:

In DMM, the decimal part belongs to the minutes; in DD, it belongs to the degrees. Minutes and seconds are angular units: 1° contains 60′ and 1′ contains 60″. They are not minutes and seconds of time.

Decimal degrees are convenient to copy and share. Google Maps accepts all three formats when correctly written. To avoid confusion, use decimal points and always enter latitude first.

How to convert degrees, minutes and seconds to decimals

Converting between formats is straightforward: the calculation uses base 60. For a positive coordinate, the DMS-to-decimal formula is:

For a south or west coordinate, calculate the absolute value first, then apply the minus sign to the entire result. Do not subtract only the degrees while leaving minutes and seconds positive. For DMM, simply divide decimal minutes by 60 and add them to the degrees.

From decimal degrees to DMS

1. Take the integer part of the absolute value: these are the degrees.
2. Multiply the fractional part by 60: the integer part of the result gives the minutes.
3. Multiply the fractional part of the minutes by 60 to obtain seconds.
4. Restore the sign or hemisphere letter and round only at the end.

For example, 41.890378° gives 41°, then 0.890378 × 60 = 53.42268′, and finally 0.42268 × 60 = 25.3608″. Rounded, the result is 41° 53′ 25.36″.

For a quicker calculation, use GeographicLib’s GeoConvert, which reads and converts geographic, UTM/UPS and MGRS coordinates using WGS84. Its documentation explains accepted formats. To convert a GPX or KML track instead, see the guide to GPS file conversion.

Keeping six decimal places does not mean the measurement has that accuracy. The number of digits describes the representation; accuracy depends on the data and how it was obtained.

Cartography, datums, WGS84 and UTM coordinates

Latitude and longitude are geographic coordinates. Representing Earth’s curved surface on a map requires a projection: the resulting coordinates can be expressed on a plane, often in metres. This distinction matters on a hike when transferring a GPS position onto a paper map.

A geodetic datum defines the reference to which coordinates relate, through a model of Earth and its positioning. The ellipsoid is the smooth mathematical surface approximating Earth’s shape; it does not, by itself, fully define the reference. GPS uses WGS84, the World Geodetic System 1984.

UTM, Universal Transverse Mercator, is a projected coordinate system dividing the globe into 60 zones, generally 6° of longitude wide. A UTM position requires a zone, hemisphere, easting, northing and geodetic reference. Easting and northing are expressed in metres. UTM covers latitudes from 80° S to 84° N; UPS is normally used in the polar regions.

Maps from Italy’s Istituto Geografico Militare belong to different series and reference systems: “UTM” alone is not enough to configure a GPS receiver. Check the legend, datum, zone and hemisphere. Italian cartography includes Roma40, ED50 and ETRS89 in its different realisations; IGM documents transformations through Verto.

To plot a point on a UTM map, first convert its coordinates into the map’s reference system. Then identify the grid square and measure east and north using the correct scale. Three-dimensional Cartesian coordinates also have their uses: they describe position through three axes, while geodetic coordinates use latitude, longitude and ellipsoidal height.

How to find an address’s GPS coordinates in Google Maps

Let’s use Milano Centrale station as an example. Enter its name in Google Maps: for such a well-known place, there is no need to know the full address. Zoom in and select the point you need, such as a meeting location.

On a computer

1. Open Google Maps and search for the address or place.
2. Right-click the precise point on the map.
3. Read the decimal coordinate pair at the top of the menu; click the numbers to copy them.

The example 45.486121, 9.204369 takes you to the Milano Centrale area. The first number is latitude and the second is longitude. Moving the point changes the values: there is no single coordinate pair for the whole station.

On Android, iPhone and iPad

In the app, touch and hold an unlabelled point on the map to drop a pin. On Android, the coordinates appear in the search box; on iPhone and iPad, they appear in the place sheet. Google Maps Help provides the procedure for each device.

Searching for a place using coordinates

Paste the pair into the search box. For decimals, write 45.486121, 9.204369, using a dot within each number. A sequence such as 45,486121, 9,204369 is ambiguous. Check that latitude lies between −90 and +90, longitude between −180 and +180, and signs match the hemisphere.

Once you have found the point, you can share it or use it to orient yourself. The same principle underlies photo geotagging, which associates pictures with their geographical position.