Natural Area Code
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The Natural Area Code (or Universal Address) is a proprietary geocode system for identifying an area anywhere on the Earth, or a volume of space anywhere around the Earth. The use of thirty alphanumeric characters instead of only ten digits makes a NAC shorter than its numerical latitude/longitude equivalent.
Instead of numerical longitudes and latitudes, a grid with 30 rows and 30 columns - each cell denoted by the numbers 0-9 and the twenty consonants of the Latin alphabet - is laid over the flattened globe. A NAC cell (or block) can be subdivided repeatedly into smaller NAC grids to yield an arbitrarily small area, subject to the ±1 m limitations of the World Geodetic System (WGS) data of 1984.
A NAC represents an area on the earth—the longer the NAC, the smaller the area (and thereby, location) represented. A ten-character NAC can uniquely specify any building, house, or fixed object in the world. An eight-character NAC specifies an area no larger than 25 metres by 50 metres, while a ten-character NAC cell is no larger than 0.8 metres by 1.6 metres.
Using a base 30 positional numeral system, NAC uses an alternate method which excludes vowels and avoids potential confusion between "0" (zero) and "O" (capital "o"), and "1" (one) and "I" (capital "i"):
For example, the ten-character NAC for the centre of the city of Brussels is HBV6R RG77T.
Extension to three dimensions
The full NAC system provides a third coordinate: altitude. This coordinate is the arctangent of the altitude, relative to the Earth's radius, and scaled so that the zero point (000...) is at the centre of the Earth, the midpoint (H00...) is the local radius of the geoid, i.e. the Earth's surface, and the endpoint (ZZZ...) is at infinity.
For example, the three-dimensional NAC for the centre of Brussels, at ground level, is HBV6R RG77T H0000.
The NAC system is heavily encumbered by Intellectual Property (IP) restrictions. NAC Geographic Products Inc claims copyright on the rudimentary divide-by-30 algorithm and base-30 alphabet used to convert from latitude/longitude to NAC.  This is unusual, and may not be valid, for such a simple and straightforward algorithm.
- "The Natural Area Coding System is a proprietary standard that requires licenses to use in any applications except for those by end users. Any uses of the Natural Area Coding System or any of its derived systems including any maps with NAC grids and any intelligent devices such as computers, GPS receivers, mail sorting equipment in either hardware or software that have the capability to input, display, retrieve, store, or process the Natural Area Coding System or any of its derived systems require licenses from NAC Geographic Products Inc." 
This means that without a license (and if your country recognizes these rudimentary claims), user cannot write software to convert between NAC and other systems such as latitude/longitude. These terms may impose a serious limit to the widespread acceptance of NAC.
- "Legal and Licensing". www.nacgeo.com. Retrieved 2020-03-23.
- Eric Freibrun (Feb 2, 1995). "Intellectual Property Rights in Software – What They Are and How to Protect Them". freibrunlaw.com. Retrieved Oct 9, 2020.
- "Legal and Licensing". www.nacgeo.com. Retrieved 2020-10-10.