What is the purpose of the zone-based false origin in UTM?

• A. To ensure positive coordinates within each zone.
• B. To identify zone numbers.
• C. To measure height.
• D. To link zones to Greenwich.

Answer: (A)

The main idea is to keep all projected coordinates positive within each zone. In UTM, the world is split into 60 zones, each using a transverse Mercator projection centered on a specific meridian. Eastings are measured from that central meridian, so without a shift some locations would have negative values west of the center. By adding a false easting of 500,000 meters at the central meridian, every point in a zone ends up with an easting between about 0 and 1,000,000 meters. This makes coordinates simple, consistent, and positive. Northings are handled separately (positive in the northern hemisphere from the equator; a large false northing is used in the southern hemisphere). So the zone-based false origin’s purpose is to ensure positive coordinates within each zone, rather than to identify the zone, measure height, or link zones to Greenwich.