For example, it would not be useful when mapping all of the conterminous United States. Each zone is segmented into 20 latitude bands. Latitude bands "A" and "B" do exist, as do bands "Y" and Z". They cover the western and eastern sides of the Antarctic and Arctic regions respectively. A convenient mnemonic to remember is that the letter "N" is the first letter in the northern hemisphere, so any letter coming before "N" in the alphabet is in the southern hemisphere, and any letter "N" or after is in the northern hemisphere.
The combination of a zone and a latitude band defines a grid zone. The zone is always written first, followed by the latitude band. For example see image, top right , a position in Toronto, Canada, would find itself in zone 17 and latitude band "T", thus the full grid zone reference is "17T".
The grid zones serve to delineate irregular UTM zone boundaries. They also are an integral part of the military grid reference system. A note of caution: A method also is used that simply adds N or S following the zone number to indicate North or South hemisphere the easting and northing coordinates along with the zone number supplying everything necessary to geolocate a position except which hemisphere.
However, this method has caused some confusion since, for instance, "50S" can mean southern hemisphere but also grid zone "50S" in the northern hemisphere. These grid zones are uniform over the globe, except in two areas. The three grid zones 32X, 34X and 36X are not used. The easting is the projected distance of the position from the central meridian, while the northing is the projected distance of the point from the equator. The point of origin of each UTM zone is the intersection of the equator and the zone's central meridian.
In order to avoid dealing with negative numbers a false origin is used. It is often said that UTM is a military system created by the U. At that time, the goal was to design a consistent coordinate system that could promote cooperation between the military organizations of several nations.
Before the introduction of UTM, allies found that their differing systems hindered the synchronization of military operations. Conferences were held on the subject from to , with representatives from Belgium, Portugal, France, and Britain, and the outlines of the present UTM system were developed.
By , the U. Army introduced a system that was very similar to that currently used. Here is a convenient way to find the zone number for a particular longitude. Any answer greater than an integer is rounded to the next highest integer and you have the zone. Round up to How are different map projections used? The method used to portray a part of the spherical Earth on a flat surface, whether a paper map or a computer screen, is called a map projection.
No flat map can rival a globe in truly representing the surface of the entire Earth, so every flat map misrepresents the surface of the Earth in some way.
A flat map can show one or more--but never all Why don't U. Filter Total Items: 2. Geological Survey. Year Published: Maps for America: cartographic products of the U.
Geological Survey and others "Maps for America" was originally published in as a Centennial Volume commemorating the Geological Survey's hundred years of service - in the earth sciences. Thompson, Morris M. Date published: July 5, Date published: August 18, Filter Total Items: 7.
List Grid. December 18, August 18, Attribution: Core Science Systems. July 22, The illustration below Figure 2. As you can imagine, you can't flatten a globe without breaking or tearing it somehow.
Similarly, the act of mathematically transforming geographic coordinates to plane coordinates necessarily displaces most but not all of the transformed coordinates to some extent.
Because of this, map scale varies within projected plane UTM coordinate system grids. The distortion ellipses plotted in red help us visualize the pattern of scale distortion associated with a particular projection.
Had no distortion occurred in the process of projecting the map shown in Figure 2. As you can see, the ellipses centered within the highlighted UTM zone are all the same size and shape. Away from the highlighted zone, the ellipses steadily increase in size, although their shapes remain uniformly circular. This pattern indicates that scale distortion is minimal within Zone 30, and that map scale increases away from that zone. Furthermore, the ellipses reveal that the character of distortion associated with this projection is that shapes of features as they appear on a globe are preserved while their relative sizes are distorted.
Map projections that preserve shape by sacrificing the fidelity of sizes are called conformal projections. The plane coordinate systems used most widely in the U. The Transverse Mercator projection illustrated above Figure 2. Fifty-nine variations on this projection are used to minimize distortion in the other 59 UTM zones.
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