FAQ

Frequently asked questions concerning geodesy, surveying and navigation.

Terrestrial curvature

Computation of the influence of terrestrial curvature and refraction.

For a distance (D) of 349 kilometres (width of Switzerland from east to west), the apparent height difference due to terrestrial curvature (E) and refraction (R) would be -8318 metres.

The illustrated example shows the commonly known effect of the apparently disappearing ship on the horizon of a large lake with increasing distance from the point of observation. 

Terrestrial curvature

D [km] E[m] E-R[m] Remark
1 0.08 0.07  
10 7.8 6.8  
100 780 680  
221 3834 3335 Switzerland: N-S
349 9560 8318 Switzerland: E-W

Formula

E = D*D / 2r 

E-R = 0.87 * D*D / 2r 

The figure of 6370 kilometres was used for the earth's radius. 

The figure 0.87 is obtained from 1 minus the refraction coefficient (~0.13).

National coordinates / GPS

What do I have to enter in my GPS receiver to obtain the Swiss national coordinates indicated on the national maps?

Reference system "CH1903" and map projection (grid) "SWISSGRID". 

Geographic coordinates of Swiss cities

I would like to know the geographic coordinates (latitude and longitude in degrees, minutes and seconds) of cities in Switzerland. Can you tell me how I can obtain this information?

The geographic coordinates for Switzerland are indicated in the margins of our national map series (1:25 000 to 1:100 000). Approximate values for lager cities may be obtained from these. The geographic coordinates network is shown on the 1:500 000 national map with information about the national coordinates in the margins. Our CD-ROMs (SwissMap 100" or "SwissMap 50" provide an easier and more modern method for obtaining geographic coordinates.

The online service NAVREF allows direct transformation between national coordinates and geographic coordinates.

An external data base with worldwide coordinates of places can be found at geonames.org

Transformation of WGS84 <-> national coordinates

How can you transform geographic coordinates (latitude / longitude / ell. height in WGS84) to Swiss national coordinates (y / x / H in LV03) or vice versa?

a) Manual input of single points:

On the following web page the NAVREF software is available online for conversion in the metre range: 

b) Entering coordinate files for conversion with greater accuracy:

On the following web page a series of points can be transformed online into all applicable reference systems and reference frames in Switzerland, using several common data formats: 

If you precisely measure on the 1: 25 000 national map or look for the coordinates with a GPS device outside, you will find the point directly above the rock face to the west of Chli Aelggi. But this site is practically inaccessible. In view of this, the geographic centre has been shifted by around 500 metres to the southeast.

In the municipality of Sachseln (canton of Obwalden) the idea of marking this point was welcomed, and the municipality subsequently made the site available free of charge. swisstopo donated a triangulation pyramid and a local club constructed a wall in the shape of Switzerland around the pyramid.

An aluminium panel was installed with a map of Switzerland showing the geographic centre in all directions in the respective national languages.

Height reference for Switzerland

Height reference for Switzerland

Vermessung am Pierre du Niton
Pierre du Niton

The reference for all height measurements in Switzerland is «Repère Pierre du Niton» in the harbour of Geneva. It is used for all surveying and maps in Switzerland.

Its original height, the «old reference», 376.86 metres above the mean sea level of the Mediterranean (tide gauge in the harbour of Marseilles) was determined in the 19th century based on the height of Mount Chasseral, which had been determined inaccurately by French engineers and geographers from the tide gauge in Marseilles. This original height was used for the old height observations (precise levelling, 1864 to 1891) as well as for the Dufour and Siegfried Maps.

At the beginning of the 20th century, within the scope of the national survey, this reference was recalculated. In 1902, a study by J. Hilfiker was published in which the height of «Repère Pierre du Niton» was computed from different tide gauges in Europe. The official figure of 373.6 metres (i.e. the "new reference") was introduced in 1902 and was 3.26 metres lower than the old reference height.

The old heights, i.e. in the Siegfried Map, are therefore 3.26 metres above the official heights in the national maps and in all cadastral plans in Switzerland. Despite concerted efforts to inform professional organisations of this change, the implementation of the new height progressed very slowly, especially in civil engineering and the construction industry, and this has often led to errors and confusions concerning heights.

Definition of the 1902 reference

  • Controlled via four connections to sea level
  • Obtained from the tide gauge in Marseilles and rounded to 373.6 metres above sea level

Repère Pierre du Niton applications

Applications
New reference since 1902
Old reference before 1902
Precise levelling (LN02) Precise levelling
National control survey (LV03) Dufour Map
Cadastral survey Siegfried Map
National maps  

Federal Office of Topography swisstopo Seftigenstrasse 264
P.O. Box
3084 Wabern
Tel.
+41 58 469 01 11

E-mail


Relevant authority

Geodesy and Federal Directorate of Cadastral Surveying
E-mail


Print contact

Federal Office of Topography swisstopo

Seftigenstrasse 264
P.O. Box
3084 Wabern

Map

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