CH1903 (Swiss Coordinate System 1903 | EPSG:4149)

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Introduction

CH1903 is the widely used national coordinate system of Switzerland, based on the geodetic datum established in 1903. It is a projection coordinate system covering the whole of Switzerland, developed to enable precise geospatial information management and mapping of a country with mountainous terrain. The reference ellipsoid used is Bessel 1841, and the projection method is the Oblique Mercator Projection. This coordinate system has long been used by the Swiss National Cartographic Office (Swisstopo) and has become a standard in many fields such as topographic mapping, surveying, civil engineering and infrastructure planning. In recent years, Switzerland has gradually transitioned to the higher-precision CH1903+ (EPSG:2056) coordinate system, but a large amount of historical data is still stored based on CH1903.

Coordinate System Composition

Longitude and latitude system: Longitude and latitude are expressed in degrees according to the Swiss geodetic system.
Plane rectangular coordinates (LV03 format): CH1903 uses two axes, east (E) and north (N), to express positions in meters.
**Datum origin: **The original Bern Observatory is used as the datum point, and an artificial offset is added for convenience and practicality.
**Ellipsoid definition: **Based on the Bessel 1841 ellipsoid, the accuracy of ground observations is improved.

Pros

Optimized for domestic applications: optimized for Swiss terrain and geographical features, enabling high-precision map production.
**Highly reliable: **with a history of more than 100 years, it is compatible with a large number of existing data assets.
Compliant with national standards: highly consistent with official geographic data released by the Swiss government and local authorities, suitable for use in public projects.

Cons

Not applicable to global standards: Not directly compatible with international standard coordinate systems such as WGS84, and conversion is required.
Limited accuracy: It is slightly insufficient when facing the requirements of modern measurement technology for millimeter-level accuracy.
**Issues of migration to CH1903+: **Since CH1903+ is the recommended standard for the future, CH1903 is often regarded as a legacy system (Legacy) and will be gradually phased out in some applications.

Application Scenario

CH1903 is mainly used in topographic surveying, road planning, railway network construction, mountain map production, and land management in Switzerland. Especially in Switzerland, where mountains are widespread, it has long provided a stable and consistent measurement basis. In the fields of architecture and civil engineering, CH1903 is also an important reference coordinate system for public infrastructure construction, which can be smoothly connected with existing CAD and GIS data. Even in geospatial projects such as tourism, disaster prevention management, and national park planning, CH1903 is still widely used.

Example

Added mesh for CH1903/LV03 to the map.