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GPS Coordinates: Decimal Degrees vs Degrees-Minutes-Seconds

The same exact location can be written two completely different ways β€” and knowing why helps you tell precise coordinates from rounded ones.

Latitude and longitude measure two different axes

Latitude measures north-south position, running from 0Β° at the equator to Β±90Β° at the poles. Longitude measures east-west position, running from 0Β° at the prime meridian to Β±180Β° at the antimeridian.

Degrees-minutes-seconds (DMS)

A DMS coordinate like 37Β°33'42"N splits each degree into 60 minutes and each minute into 60 seconds, mirroring exactly how clock time is divided β€” a legacy of the same base-60 navigational tradition.

Decimal degrees (DD)

A decimal degrees coordinate like 37.5617Β°N expresses the same position as a single decimal number. This is the format most digital mapping systems and GPS devices use internally, even when they display DMS to the user.

The conversion formula

DD = degrees + minutes/60 + seconds/3600. In decimal degrees, direction is shown by a positive or negative sign instead of an N/S/E/W letter suffix.

What each decimal place actually buys you

Roughly speaking, each additional decimal place narrows precision by about a factor of ten: 2 decimal places locate a position within about 1 km, while 5 decimal places narrow it down to roughly 1 meter β€” which is why copied coordinates sometimes look needlessly long.

Sign convention replaces compass letters

In decimal degrees, negative latitude means Southern Hemisphere and negative longitude means Western Hemisphere, replacing the N/S/E/W letters used in DMS notation.

Why two formats exist for the same coordinate

DMS grew directly out of centuries of navigation and surveying tradition, using the same base-60 division as clock time. Decimal degrees became dominant once computers needed a format that's trivial to store, compare, and perform math on directly β€” which is why most modern devices convert internally to decimal degrees even when the interface displays DMS for a human reader.

Why precision matters more than it looks

A coordinate truncated to just 2 decimal places can be off by close to a kilometer from the intended point β€” fine for marking a general city location, but a real problem for a delivery address or a property boundary. How many decimal places to keep depends entirely on what the coordinate is actually being used for.

Frequently Asked Questions

How many decimal places should I use for an exact address?

5 to 6 decimal places is generally enough to pinpoint an exact building or location to within roughly a meter or less. Beyond that, additional decimal places rarely add meaningful real-world precision.

Why do some maps show a negative longitude?

A negative value in decimal degrees indicates the Western Hemisphere (west of the prime meridian), or the Southern Hemisphere in the case of latitude β€” this replaces the W/S letter suffix used in DMS notation.