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. 

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).

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". 

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

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: 

• NAVREF
  

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: 

• REFRAME 

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.

Where is the centre of the biggest possible circle within Switzerland that touches the border but does not cross it at any point? The centre of this circle is actually the point that is located furthest from our neighbouring countries.

swisstopo has done this calculation precisely and found out that this point is located in the municipality of Uetendorf in the Canton of Bern. And, to be exact, the point in our country that is furthest from the border can be found in a field named Silbermoos at the coordinates 2 610 172/1 181 300.

With help of geographical information systems, this point can be precisely determined. You go from the border and draw parallel lines at an ever-greater distance from the border. The point you are looking for is located in the last remaining area. This process is illustrated in the following drawing.