DHDN (Deutsches Hauptdreiecksnetz)
Jun 12,2026

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Introduction

DHDN (Deutsches Hauptdreiecksnetz) is the old national geodetic datum of the Federal Republic of Germany, corresponding to EPSG code 4314. It is also often referred to as the Lauenberg Datum or Potsdam Datum. Based on the Bessel 1841 ellipsoid, its original fundamental point was TP Lauenberg. After this point was destroyed by sand and gravel extraction, the Helmert Tower in Potsdam became the new central point. DHDN served as the common coordinate basis for land surveying in the old federal states of Germany. With the advent of satellite geodetic techniques, the importance of the hierarchical triangulation network gradually declined. Starting in the 2010s, DHDN has been replaced by the ETRS89 coordinate system. Today, it is mainly used for onshore geodetic surveying and national digital mapping in the former West German states, covering areas such as Baden-Württemberg and Bavaria.

Coordinate System Composition

Datum Framework: The datum is named Deutsches Hauptdreiecksnetz (German Principal Triangulation Network). It is a national geodetic datum established through traditional triangulation. The original fundamental point was TP Lauenberg, later replaced by the Helmert Tower in Potsdam as the core reference point. The coverage area includes all onshore areas of the former West Germany, used to unify the national geodetic coordinate reference.
Reference Ellipsoid: Uses the Bessel 1841 ellipsoid, with parameters: semi-major axis 6,377,397.155 meters and reciprocal flattening 299.1528128. It is a classic ellipsoid model widely applied in modern European geodetic surveys.
Geodetic Datum Definition: Uses DHDN as the datum plane. Also defines transformation parameters to WGS84 (slightly varying between sources, with typical TOWGS84 parameters of [598.1, 73.7, 418.2, 0.202, 0.045, -2.455, 6.7]), used for coordinate transformation to modern systems like WGS84.
Prime Meridian: Uses the Greenwich Meridian as the prime meridian, consistent with the international standard for longitude origin. Angular unit is degrees.
Coordinate Axis Definition: A 2D geographic coordinate system with two axes: the first axis is latitude (Lat), positive north; the second axis is longitude (Lon), positive east. The unit for both axes is degrees.

Pros

Strong Historical Compatibility: As the fundamental datum for land surveying, official control points, traditional topographic maps, and cadastral maps in Germany's old federal states, most existing spatial data was generated based on this system, allowing direct compatibility with German historical survey records.
Regional Accuracy Suitability: Optimized for the German national territory, achieving meter to sub-meter level accuracy for individual point measurements within Germany, meeting the accuracy requirements for traditional engineering surveys, cadastral mapping, and topographic mapping.
Mature Transformation System: A well-established transformation scheme covering all of Germany and its federal states has been developed. It allows transformation to modern systems like ETRS89/WGS84 (e.g., via NTv2 grid methods) with standardized workflows compatible with most GIS software.

Cons

Outdated Technical Framework: Based on traditional triangulation, relying on ground-based manual observations. Its overall accuracy and stability are far below those of modern satellite-based datums, making it unsuitable for direct use with GNSS satellite positioning.
Limited Applicability Range: Optimized only for the German national territory. Accuracy degrades significantly outside Germany, making it unsuitable for large-scale or global spatial data applications.
Phased Out / Discontinued: German authorities completed the transition to the ETRS89 coordinate system starting in the 2010s. Newly produced official surveying and cadastral data no longer use this datum, and long-term maintenance support is gradually ceasing.
Regional Parameter Deviations: Slight variations exist in WGS84 transformation parameters between different regions and sources. The accuracy of a single, uniform transformation across the whole area is slightly lower than using regionally specific transformation schemes, potentially introducing coordinate deviations.

Application Scenario

The core applications of DHDN (EPSG:4314) revolve around traditional surveying and mapping in Germany. Initially serving as the national geodetic datum supporting nationwide triangulation, it has long provided the coordinate reference for national digital mapping, cadastral surveying, and official topographic information systems across all German states. It can also be used for coordinate matching of existing historical German geospatial data. Standardized transformation workflows allow it to be used with common desktop GIS tools like QGIS and ArcGIS, as well as web and mobile map services, and it supports coordinate transformation to modern systems like WGS84 and ETRS89 for compatibility with newer geoinformation applications.