Navigation maps are printed with a coordinate grid that is a two-dimensional projection of the three-dimensional Earth surface, based on a given Coordinate System. Historically the countries over the world use many different Coordinate Systems.
Earth is shaped not like a sphere; it is a geoid that has no exact mathematical definition and whose form can be at best approximated by an ellipsoid. To make an exact projection of a region into a Coordinate System, the region is first projected onto a so-called reference ellipsoid that would fit the region best. The reference ellipsoid is mathematically defined and can be used for a Coordinate System projection. Historically countries all over the world developed and used different and often more than one local and global Reference Systems.
Each country uses or recently used its own Coordinate and Reference System (Geodetic Datum). In some countries multiple competing systems where used simultaneously. Federal Republic of Germany is a good illustration of this situation:
DHDN (old blocks)
In the old States of the Federal Republic as well as in unified Germany was used, and is still in use, the Potsdam Datum (DHDN) based upon the Bessel Ellipsoid. The projection is normally made into the Geographic Coordinate System or into the Gauss-Krueger Coordinate System with three degrees wide meridian strips. Small-scale maps were often made using various Lambert Coordinate Systems.
The former German Democratic Republic used the System S42/83 based on a Krassowskij ellipsoid and projection into the Gauss-Krueger Coordinate System with six degrees meridian strips.
RD83 / PD83
Some of the Federal Republic new states use the Rauenberg Datum RD83 and the Rauenberg Datum PD83 projected onto the Bessel Ellipsoid. The projection is uniformly made to the old Federal Republic States in the Geographic Coordinate System, or to the Gauss-Krueger Coordinate System with three degrees wide meridian strips.
On the Day of German Unity, October 3rd 1990, representatives of the Basic Surveying of the old and new federal States developed a draft which had a standardised, geodetic "Reference System" in the unified Germany as its objective. This could only happen by definition, while connecting the historically grown Reference Systems DHDN, S42/83, RD83 and PD83 described above to a new DHDN90. The DHDN90 can be considered as a Compound Coordinate Reference System (CCRS).
Military topography uses a NATO standard based on the European Datum ED50 with the International Ellipsoid from Hayford and projection to the UTM Coordinate System or to the Military Grid Reference System (MGRS).
Thanks to the growing popularity and wide use of the American satellite-based Navstar GPS (Global Positioning System), internationally and of course within the Federal Republic of Germany, there is increased acceptance of the worldwide WGS84 (World Geodetic System), introduced in 1984. It become even more important after the intentional degradation of the GPS signal was lifted in Mai 2000.
With Galileo, the European satellite positioning system, which is operational at the end of 2010, and with the to the same time modernized Navstar GPS (GPS III), the development of the modern satellite navigation continues.
The sheer multitude of different Coordinate and Reference Systems did and still does considerably complicate multinational space-oriented projects. Proliferation of GIS technologies driven by increased use of GPS and globalization of trade, politics, and environmental protection adds to demand for more multinational geodetic data. An important condition for progress in this area is a unified Coordinate System along with a unified Reference System. The global UTM Coordinate System (Universal Transversal Mercator Projection) with 60 meridian strips can be used worldwide. The ETRS89 (European Terrestrial Reference System 1989) based on the ETRF89 (European Terrestrial Reference Frame) was analyzed and measured by a combination of various modern navigational methods, is assessed as European ReferenceSystem.
In the 1990-ties the Surveying Authorities of most European countries decided to use for extensive topographic and cadastral projects the UTM Coordinate System and the ETRS89 Reference System. It is based on the GRS80 ellipsoid (Geodetic Reference System). UTM coordinates are used for projection in most maps across Europe.
There is another big advantage in moving to the modern Coordinate and Reference Systems. The American Satellite Navigation System GPS data is referenced to the WGS84 (World Geodetic System). The minor difference between WGS84 and ETRS89 makes it possible to use GPS data in modern maps directly, with negligible impact on accuracy.
Exact datum shifts from DHDN90 to the modern ETRS89 are possible with gridfiles of the NTv2 standard since 2008.
Planning and executing business and scientific projects, topographical, cadastral and public works, require topographical documentation, maps, blueprints and digital data, containing large amounts of project-related positions and coordinates. As long as the traditional Coordinate and Reference Systems are still used along with the modern systems there will be need for translation of spatial data from traditional systems into the modern Europe and worldwide system. This means that during the transition period there will be a high-volume data processing of geodetic datum shift Coordinate Transformations from traditional systems into the modern systems. The program TRANSDAT was developed for conversion of spatial data between various Coordinate and Reference Systems across the whole world, as well as for maintenance and storing of spatial data. The program is easy to use, can perform calculations on large amounts of data quickly and with high accuracy. It is flexible and can be used in many applications.
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