For people with moderate geodetic expertise, coordinates, consisting of long sequences of numbers and letters that indicate a unique point on the Earth, are not easy to understand. This article is a crash course, explaining the calculation methods and their history.
According to the UTM Coordinate System, the globe is divided into vertical UTM zones of 6 longitudes each. These zones are arranged round the equator, to be compared with orange peels. Starting eastwards at 177 degrees West, they are numbered from 1 to 60. Each UTM zone is regarded as an individual Cartesian Coordinate System. The origin for each UTM zone is the intersection of the equator with the corresponding central meridian. The easting of the central meridian is shifted by 500.000 meters, in order to obtain exclusively positive values. For the same reason, when being displayed on the southern hemisphere, the northing is shifted by 10.000.000 meters.
|•||UTM Zone Coordinates||32439596 / 5967780||Easting and Northing|
|•||33045270 / 5989604||in adjacent UTM zone|
|•||MGRS/UTMref/UTM Reference System||32UME3959667780||Recording exact to the meter|
|•||32UME3967||Recording to the kilometer|
|•||UTM Grid Coordinates||32U4395965967780||Grid coordinate|
|•||Reduced UTM Coordinates||439596 / 967780||Reduced Easting and Northing|
|•||439596 / 5967780||Reduced Easting|
The examples show the multiple possibilities of UTM coordinates. The user may chose, which display mode is most suitable for the purpose in question. Here, we are going to explain the exact meaning of the individual numerals and letters, appearing within the coordinate. In the following, we are going to show ways to convert UTM coordinates from one display mode to another.
UTM Zone Coordinates
The most common representation is the one of UTM coordinates with an easting and a northing. The coordinates within a UTM zone are metrical and perpendicular to each other. The easting is preceded by the number of the UTM zone. Our example, as a complete UTM zone coordinate, is represented as follows:
The point is located in the UTM zone 32, which is based at the central meridian, 9 degrees eastern longitude. Because the value 439596 is below 500000, the point is located exactly 60404 meters west of the central meridian (500000 m - 439596 m = 60404 m). To the North, the point is exactly at a distance of 5967780 meters from the equator.
The point is now located in the UTM zone 33, which is based at the central meridian, 15 degrees eastern longitude. Because the value 045270 is below 500000, the point is located exactly 454730 meters west of the central meridian (500000 m - 045270 m = 454730 m). To the North, the point is exactly at a distance of 5989604 meters from the equator.
MGRS / UTMref / UTM Reference System
For military purposes, UTM coordinates are represented in the "Military Grid Reference System" (MGRS) or "UTM Reference System" (UTMref). To indicate the geographical latitude, the meridians are subdivided into UTM bands of 8 degrees along the parallels that are denominated with letters. The UTM zones, in turn, independent of the UTM bands, are divided into squares with a lateral length of 100 km each, positioned parallel to the central meridian. The UTM squares are denominated with letter pairs. A point, exact to the meter, is notated with 5 digits of the east and of the north position, respectively, within the UTM square. Again, we take the coordinates of the beacon "Red Sand":
The point is located in the UTM zone 32. It is the meridian with the central meridian at 9 degrees eastern longitude. Also, the point is located in the UTM band U, which extends between 48 and 56 degrees northern latitude. It is located as well within the UTM square ME, 100 km west of the central meridian and 5900 km north of the equator. The position exact to the meter is 39596 meters east of the south western corner of the UTM square and 67780 meters north of the same. The accuracy of a UTMREF coordinate can be varied by the (even) number of digits, in order to describe this way a larger or smaller area. These are some examples with differing accuracy:
|•||32UME3959667780||exact to the meter|
|•||32UME395677||exact to 100 meters|
|•||32UME3967||exact to 1 kilometer|
|•||32UME||exact to 100 kilometers|
The conversion program TRANSDAT can calculate UTMref coordinates in different accuracy levels. The picture shows the necessary settings. Because UTMref coordinates are not described as usual with a northing and an easting, but only by way of a combination of characters, the second entry field remains empty.
UTM Grid Coordinates
UTM Grid Coordinates are represented in a slightly different way. The UTM grid coordinate of the beacon "Red Sand" looks as follows:
The point is located in the UTM zone 32 and in the UTM band U. The exact position is 60404 meters west of the central meridian (500000 m - 439596 m = 60404 m). To the north, the point is at an exact distance of 5967780
Reduced UTM Coordinates
Unfortunately, the zone number is not always included in UTM zone coordinates. This kind of coordinate display is often used, presuming the knowledge of the UTM zone. When showing the easting, the zone number is then simply left out. In fact, this is not an official notation but a result of certain laziness. Originally, reduced coordinates where due to technical reasons. To reduce the effort, the number of digits has been cut. From the side of the Army, additional criteria were brought in. In their systems, an extra entry field had been added for the zone notation (e.g. 32 or also 32U). In the Civil Environment, others copied the idea. Our test coordinate might look as follows:
In this case, the UTM zone has to be guessed, calculated or at least taken as a constant value. The author of this paper do not doubt in the necessity of indicating the full UTM coordinate. Given the fact, that only coordinates from the same zone may be calculated, incomplete UTM coordinates can be compared to street numbers without indicating the street.
Sometimes, also the first digit of the northing (1000 km digit) is blanked. For the area of Germany it is always a 5, apart from a small area in the north of the country:
In this case, not only the UTM zone, but also the 1000 km digit of the northing must be known.
The TRANSDAT Program
TRANSDAT was developed by the German company Killet Software Engineering. The program is in productive use in Europe, the United States and other countries worldwide for the professional conversion between international and national Coordinate Systems and Reference Systems - fast and with highest quality results. TRANSDAT supports all by the INSPIRE directive prescribed ETRS89 conversions with NTv2 grid data, e,g. Gauss-Kruger / DHDN to UTM / ETRS89 with BeTA2007. The NTv2 standard with national gridfiles is worldwide full supported. Apart from the given worldwide and state-specific systems, your own personal Coordinate Systems and geodetic Reference Systems can be defined with Helmert (Bursa / Wolf, ISO19111) or Molodensky Parameters. Calculations can be performed with coordinates entered directly or loaded from files in various formats (Text, CSV, SDF, dBase, ArcShape and ArcGenerate). For more detailed information, please go to our website http://www.killetsoft.de/p_trda_e.htm.
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