Article 55292 of sci.geo.satellite-nav: Path: matra.meer.net!news1.best.com!news.maxwell.syr.edu!news-peer.sprintlink.net!news.sprintlink.net!Sprint!newsfeed.internetmci.com!204.71.76.137!news.campus.mci.net!n-f-m From: Jack Yeazel Newsgroups: sci.geo.satellite-nav Subject: UTM Trivia Date: Tue, 13 Jan 1998 16:18:54 -0500 Organization: Un-organized Lines: 33 Message-ID: <34BBDA3E.502A@peachnet.campus.mci.net> Reply-To: river5@peachnet.campus.mci.net NNTP-Posting-Host: s02-pm02.atlanta3.campus.mci.net Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; name="Utm.txt" Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 3.01Gold (Win95; I) Content-Disposition: inline; filename="Utm.txt" Xref: matra.meer.net sci.geo.satellite-nav:55292 Someone asked for a definition of UTM... -This is all from the top of my head -so please correct accordingly! UTM, Universal Transverse Mercator, is a system of world coordinates like latitude and longitude, from 80 degrees south latitude to 84 degrees north latitude, except the measurements are in meters and UTM lines are orthogonal (are always at right-angles to each other). UTM Northing is the distance north from the equator in meters and Easting is the distance east from central meridians of (60) 6-degree-wide zones starting at longitude 180 degrees. Northing is also divided into 8-degree zones from south to north using the letters C thru X with the equator at M/N, (A,B and Y,Z being reserved for the UPS coordinate system at the poles). All measurements are POSITIVE by incorporating a system of "false" easting and northing by adding an arbitrary number to the cerntal meridans (500,000m) and 10,000,000m to the distance south of the equator in the southern hemisphere. The original definition of the meter was 1/10,000,000th the distance from the equator to the north pole -which probably no longer is exact. Due to the oblate shape of the earth, UTM (WGS-84) northing for 45 Deg. N latitude is 4,986,272m instead od 5,000,000m. For NAD-27, the northing valus is 4,986,055n. This 217m difference is related to the UTM northing errors of approximately 200m experienced by posters here on the NG with some DRG maps. This could be due to selecting the wrong datum or the map datum headers are incorrect. Jack Yeazel river5@peachnet.campus.mci.net