Coordinate-Based Addresses Explained

A coordinate-based address names a place with two numbers: latitude, which says how far north or south of the equator it is, and longitude, which says how far east or west of the prime meridian. Together they pin down one point on the Earth's surface.

How the numbers work

Latitude runs from -90 to 90 degrees and longitude from -180 to 180 when written in decimal form. Positive latitude is north and positive longitude is east. A location might be written as a pair of decimals such as 31.5204, 74.3587.

More decimal places mean more precision. Roughly speaking, each extra decimal place narrows the area by a factor of ten, so a handful of decimals is enough to identify a building.

Different formats

The same point can be written in several ways:

• Decimal degrees, the form most apps use.
• Degrees, minutes, seconds, common on printed maps and older documents.
• Degrees and decimal minutes, found in some navigation tools.

Mixing these up is one reason raw coordinates cause confusion. Another is the order: some tools show latitude first, others longitude first.

Strengths

• Universal: any mapping tool understands them.
• Precise: they can describe a very small area.
• Neutral: no language, alphabet or local naming convention is required.

Weaknesses

• Long and hard to say aloud. Reading fourteen digits over the phone invites mistakes.
• No error detection. One wrong digit gives a perfectly valid but wrong location.
• Format confusion. Signs, order and separators vary.
• No context. A pair of numbers does not tell you the country or what the place is.

These issues are why many systems wrap coordinates into shorter, more structured codes. Compare the approaches in latitude and longitude vs a location code and what makes a good location code.

When coordinates are the right choice

Coordinates are ideal for machine-to-machine exchange, surveying, mapping software and anywhere a system reads the value rather than a human. They are less ideal for notes written on parcels or messages read aloud to a driver.

Relationship to other systems

Most digital address systems are built on top of coordinates. The code is a different way of writing the same position, which is why a code can always be converted back to latitude and longitude. The general mechanism is described in how digital address systems work.