Alphanumeric Location Codes Explained

An alphanumeric location code is a short string of letters and digits that stands for a specific place. Because it draws from around thirty-six characters rather than just ten digits, it can name a precise location in far fewer characters than a pair of coordinates.

How they are built

Most systems start with a grid of cells. Each cell has a number derived from its position, and that number is written in a base larger than ten, using both letters and digits. The result is a compact code that can be converted back to the cell, and therefore to a position on the map.

Many codes are split into blocks with hyphens or spaces. Blocks make the code easier to read, copy and check, in the same way a phone number is easier with spaces.

Why use letters and digits together

• Shorter. More symbols per position means fewer positions needed.
• Neutral. Latin letters and digits are accepted in almost every form and keyboard.
• Language-free. There is no vocabulary to translate, unlike word-based systems.

Prefixes

Some systems begin the code with a prefix that identifies a region or country. A prefix helps a reader see at a glance where the code belongs and lets the system narrow down the lookup. UPCS, for example, starts with a two-letter country prefix.

Common problems

• Look-alike characters. The digit 1 and the letter I, or 0 and O, can be mixed up when handwritten.
• Case. Some systems ignore case; others are strict. Users should copy codes exactly.
• Stray spaces. Copying from messages can add spaces or line breaks.

Good systems anticipate these. See error-resistant location codes for what designers can do and what makes a good location code for the wider picture.

Using a code in practice

The sequence is the same as for any digital address: pick the place, get the code, share it, and let the receiver look it up on a map. Receivers should confirm the point on the map before relying on it. A walkthrough is in how to verify a digital address.

Example

UPCS codes follow the pattern CC-XXXX-XXXX, such as PK-1A2B-3C4D: a two-letter country prefix and two blocks of letters and digits. Each code corresponds to a 3 m x 3 m cell. Read more in UPCS code format explained.