NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Universal Transverse Mercator coordinates
From: Paul Hirose
Date: 2005 Jul 20, 10:29 -0700
From: Paul Hirose
Date: 2005 Jul 20, 10:29 -0700
Robert Eno wrote: > Essentially, the Grid reference system for northing tells you how many > meters one is from the equator. It's close, but not quite exact. An object on a UTM zone's central meridian becomes a little smaller when projected onto the grid. An object at the edge of a zone expands a little. The maximum scale error is about 1 in 1000. Directions are distorted too. Meridians (except the central meridian of the zone) are curves on the UTM grid. So if you follow a course of grid north from the equator to 4000 km northing, the track made good on the real world follows a constantly changing true course, and is not exactly 4000 km. This is true whether you assume the "real world" is a sphere or an ellipsoid.