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Wilderness Camping 'How-To,' GPS and Mapping, Origin of the UTM AcronymIf I missed some tidbit of information that you think should be here, let me know via this Comments link, which is also found at the top and bottom of almost every page on this Web site. In case you are interested just in some info on: MERCATOR -- A Mercator map projection is one developed by Gerhard Kremer, a Flemish cartographer who lived and worked in Germany the last half of his life. Gerhardus Mercator is the Latinized version of his name, and the name we know best today. Kremer/Mercator published the first map using his new projection in 1569, though the invention didn't become popular until 1599, five years after Mercator's death in 1594 at age 82. More on Mercator the man, farther down this page. Mercator PROJECTION -- The simplest non-mathematical explanation for producing a Mercator projection is slowly blowing up an inflatable globe of the earth inside a larger glass cylinder, transferring features onto the glass as the balloon slowly fills towards the ends of the tube. A paper map can be traced from the glass. It is not really done this way, of course -- nowadays it's all computer modifications of aerial photographs. A basic mathematical explanation is that a point inside the globe is used from which to project features outward onto the flat paper map. Think of a light shining inside a translucent globe, through it and out onto a flat sheet of paper wrapped in a cylinder around the globe. With the paper cylinder touching the globe around the equator a lot of the light coming out near the poles won't even hit the prospective flat map, so the light source has to be moved up and down along the globe's axis, changing the projection angle to get all features cast onto the paper. Slide the light slowly up the axis towards the north pole when doing the northern hemisphere and towards the south pole when working south of the equator. The light will also have to come away from the axis some to get a true Mercator projection. It should be obvious that accuracy near the equator is quite good, but both the balloon and light projection method produce distortion at the higher latitudes. Mercator's projection greatly exaggerates the size of all regions near the poles. This can most easily be understood through the balloon example because the balloon has to stretch so much more near the poles to touch the cylinder. This makes the land and sea areas look much, much larger than they really are. TRANSVERSE Mercator -- A transverse Mercator projection simply has the contact line going north and south (from pole to pole) instead of east and west. The transverse contact line would cross the equator twice and touch at both poles instead traveling along the equator as with the standard projection. A transverse contact is along or between the meridians (longitude lines), rather than along one of the latitude lines. Both the standard and transverse projections look and work exactly the same, and give the same results for maps. I've never seen any labeled as such, but oblique Mercator maps can be made, too. The contact line would be at an angle between the equator and poles, cross the equator in two places, but not touch the poles.
UNIVERSAL
Transverse Mercator -- To accomplish this, one narrow strip of maps is drawn, circling the globe north to south (or just the part of the circle that interests the entity paying the cartographer). The projection point is the center of the earth. Before the projection line angle spreads wide enough to start giving much distortion, the contact line is rotated a few degrees about the poles, over to a new meridian line. A new strip map is started using the same projection point at the center of the globe. Because the projection point does not move, the point is universal, a common point is used for all the maps on the whole UTM map system. GERHARD MERCATORMercator was born Gerhard Kremer, the son of a poor cobbler in Rupelmonde, Flanders, (now Belgium, near Antwerp) in 1512, then lived with a rich uncle in the small town of Gangelt. He studied for the priesthood for a short time, then entered the University of Louvain (east of Brussels) in 1530. Mercator earned a Masters degree in philosophy in 1532. Fairly early in life he followed a practice common for those who could afford it of officially Latinizing his German name. Kremer means "merchant," in German. Mercator means "world trader." Mercator married in 1536 and raised six children. Late in life his first wife and a son died, and Mercator remarried in 1586. Mercator was a victim of the Inquisition, accused of heresy against the Catholic church in 1544, probably in part for his Protestant beliefs, as well as what was thought to be suspicious activity from wide travels in search of data for his maps. He spent seven months in prison, then was released for lack of evidence. He moved almost immediately to a primarily Protestant area to reduce the threat of future persecution, then later to Duisberg, Germany (near Essen and Dusseldorf) in 1552, to reduce his exposure further. Mercator's primary scientific disciplines were cartography and geography, though he also studied mathematics, astronomy, and engraving. He made his living off of rich friends and retainers, as well as making and selling scientific instruments and globes, publishing maps, and teaching. In Germany he perfected and published his famous first map of the world using the Mercator projection in 1569. He died there in 1594 at the age of 82. Mercator was far ahead of his time in many ways. His map projection utilizes mathematical formulae that had not yet been described in 1569, when the first Mercator projection was published. John Napier's work in logarithms, Isaac Newton's and Gottfried Leibniz's work in inventing calculus, and Karl Gauss's description of differential geometry were all done from 20 to over 100 years after Mercator died. Mercator had figured out how to make his map using only a compass and a protractor. MORE MERCATOR TIDBITSThe Mercator projection keeps relative angles (orthomorphic), but surface areas get distorted in large area maps. Early sailors could put up with the distortion. What they really liked about Mercator's new mapping style was that grid angles were preserved over the whole map so it was easier for them to navigate in a "straight line" between ports. They could figure a compass bearing and stay with it. Map projections developed before this required following a constantly changing compass bearing to get from port to port. Different map users prefer projections other than the Mercator, though. For example, aviators and surveyors cannot easily work with maps using Mercator's projection. Bibliography:A technical paper on Mercator and his projection: Use your 'Back' button or 'How To' Contents | 'How To' Home | 'How To'
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