Questions and answers about the new coordinates

What is a reference frame or what are coordinates? Here you will find a compilation of the most frequently asked questions concerning the transition of the reference frame and the new coordinates.

The Swiss coordinates system was defined in 1903 and is therefore called CH1903. During the 1990s a new national survey of Switzerland was carried out using the satellite-assisted Global Positioning System (GPS). With the coordinates of these new national control points, it is now possible to carry out surveys with accuracy within the centimetre range. The new coordinates may differ from the old values by several metres. They have been given a different notation in order to avoid any confusion between the old and new coordinates. The new coordinate system is called CH1903+. The introduction of the new coordinates will take place canton by canton and be completed by 2016.

LV stands for «Landesvermessung» (national survey). The figures 03 and 95 designate the year in which the respective national survey was initiated or completed. The current reference frame, LV03 (dating from 1903) is based on observations which were carried out more than 100 years ago. The new national survey was carried out in the 1990s and completed in 1995. It forms the basis for the new reference frame LV95 (national survey 1995).

There are thousands of survey control points distributed all over Switzerland and their position and height are known and expressed as coordinates. They define the coordinates system in the terrain and constitute the reference frame for all survey carried out in Switzerland. All spatial data, i.e. data from the cadastral survey, spatial planning and construction, as well as from geographic information systems, are calculated and adjusted in this frame. The reference frame of the new national survey LV95 is defined by 31 permanently operating satellite receiver stations, plus 200 control points whose coordinates were determined to the centimetre using GPS survey methods. Together with the cantons, the Federal Office of Topography defined calculation methods for transforming the coordinates from the reference frame LV03 into the new reference frame LV95.

Coordinates are used to pinpoint the position of objects in the terrain, on maps and on plans. Thanks to unequivocal coordinates, we can let other people know where we are, or we can find a particular destination. They are also used – albeit in the background – in navigation instruments in our cars. The coordinate values represent the distance of a given point (measured in metres in the terrain) from the two coordinate axes. These come from a point of origin, and their values increase from south to north and west to east respectively.

The two coordinate axes meet at the origin of the map projection, which is also the point of origin for the coordinates. In Switzerland, this point is at the old observatory in Bern. Starting from here, the coordinates are counted in positive numbers (metres) in an easterly (y axis) and a northerly (x axis) direction.

Map projection  (oblique cylinder projection)
Map projection (oblique cylinder projection)

A map projection is used to represent the curved, three-dimensional surface of the earth on a flat, two-dimensional map. This representation is the result of geometric theories and mathematical formulae. The point of origin for the map projection is simultaneously the point of origin for the coordinates in which the main coordinate axes meet. A grid of lines at right angles on the map makes it easier to determine the coordinates of points.

Current national coordinate system CH03 of the national survey LV03
Current national coordinate system CH03 of the national survey LV03

The coordinate values at the point of origin are arbitrarily chosen values and have up to now been expressed as six-digit numbers: y = 600,000 m (east) and x = 200,000 m (north). With the introduction of the new coordinates (LV95), these values are now seven-digit numbers and called E and N, namely: E = 2,600,000 m (east) and N = 1,200,000 m (north). There are three reasons for this decision: just as for the definition used up to now, negative values to the south and west of Bern are avoided; the range of possible values excludes confusion between the east and north values, and because the reference values were shifted by 2 and 1 million metres respectively, the old LV03 and the new LV95 coordinates can be easily distinguished.

The reference frame LV03 from the beginning of the last century no longer corresponds to the technical methods and precision of modern surveying. There are discrepancies in the range of metres spread all across Switzerland. Thanks to modern satellite-assisted survey methods, coordinates can now be calculated to a degree of accuracy within the centimetre range. Accurate and globally valid coordinates are obtained using GPS observation methods. Up to now, these coordinates had to be adjusted in the inaccurate reference frame from 1903, in other words, artificially "degraded" in order to combine them with the data of existing surveys. This was very time-consuming and was also a source of errors.

Difference between the coordinates of the reference frames LV03 and LV95
Difference between the coordinates of the reference frames LV03 and LV95

The differences between the current reference frame LV03 and the new frame LV95 vary. The difference in Bern is almost zero, whereas in the Engadine Valley, in the canton of Ticino and Geneva they can reach up to 1.5 metres. Viewed over the entire country, the difference amounts to a maximum of three metres.

 

A hundred years ago the accuracy of distance measurements was considerably lower and the scale was to some extent slightly distorted. Since the point of origin for the current as well as the new coordinates system is located in Bern, the differences grow proportionally to the increasing distance away from Bern.

These differences have nothing to do with tectonic movements. They are a consequence of more accurate surveying methods. The accuracy of the national survey was increased by a factor of 100 over the past 100 years, from the metre to the centimetre range for the entire country. The crustal movements in Switzerland relative to an arbitrarily chosen reference point are approximately 1 millimetre per annum.

 

The most obvious difference is the new notation of the coordinates. The point of origin of the map projection has been assigned «new» coordinates: 

Old: CH1903     y = 600,000 m (east);     x = 200,000 m (north)

New: CH1903+ E = 2,000,000 m (east); N = 1,000,000 m (north)

The old coordinates CH1903 (LV03) have six digits whereas the new coordinates LV95 (CH03+) have seven (to the metre). In addition, the coordinate axes are clearly defined as E for east and N for north. The designations y and x often gave rise to questions because they are the other way round than is customary in geometry.

New national coordinate system CH03+ of the national survey LV95
New national coordinate system CH03+ of the national survey LV95

The reference values for the point of origin were shifted by 2 and 1 million respectively in order to avoid confusion between the old and new systems. Therefore the relationship between LV03 and LV95 can still be easily established.

It is important for every country with a modern infrastructure to be able to determine coordinates precisely and adjust them in a contemporary reference frame. It is easy to imagine what would happen if inaccurate data were used for calculating the position of tunnels or bridges. The new reference frame is also important with respect to combining our data with global survey systems (GPS) or those of our neighbouring countries. It is an indispensable prerequisite for accurate and efficient work, especially for international projects such as the European motorway and railway networks, the Lake Constance data portal, or large projects such as AlpTransit.

 

Thanks to the new reference frame LV95, the surveying methods commonly used today can be efficiently and easily applied even by non-specialists. Various calculations are simplified or have even become superfluous, sources of errors have been eliminated and the fundamental network is consistent and free of discrepancies. In the long term, the number of control points which need to be maintained can be reduced, thus leading to cost savings. Furthermore, it is easier to integrate spatial data from different sources into geographic information systems (GIS). In addition, the connection of data to global reference systems or those of our neighbouring countries, which are also carrying out similar adjustments, is facilitated.

In the long run, overall costs can be saved because surveying and maintenance are less expensive. This is thanks to simplified surveying and computation methods, as well as the reduction in error sources. It is fairly difficult to express any financial and economic benefit in precise numbers. Furthermore, the biggest gains will only become obvious once all geodata for the entire country are available in the new reference frame.

The change in the coordinate systems and reference frames from CH1903/LV03 to CH1903+/LV95 is defined in the Federal Geoinformation Ordinance (SR 510.620), which is based on the Federal Geoinformation Act of the 5th October 2001 (SR 510.62).

The most important step for the transition to the new coordinates concernes their incorporation into the official cadastral survey. Even though the cadastral survey is based on uniform guidelines, it is nevertheless organised on a canton by canton basis.

These changes are important for surveying and construction experts, as well as everyone who requires accuracies within the metre range or better in their geodata. On the other hand, there is no influence on the map content, except that the coordinates are assigned a different notation.

The new survey and the conversion of the old coordinates into the more accurate reference frame LV95 also have an influence on the coordinates of property boundary points. However, the coordinate changes of boundary points of a plot of land are all practically identical, which means that land plots as such are «shifted», of course not in reality, but only their coordinates.

No. Any adaptations of land register entries will be carried out automatically with no charges for property owners. Furthermore, property owners do not have to take any action.

If the new reference frame were not implemented, the more accurate surveys with modern instruments such as GPS (Global Positioning System) or electronic distance measurements would always have to be corrected in order to comply with the old, distorted reference frame LV03. Above all, the geodata from satellite-assisted surveys and international observation campaigns are not compatible with the old Swiss data. An emergency measure would be to equip modern surveying instruments with software which would routinely convert the recorded data into the old Swiss coordinates. In the long run, this alternative would be time-consuming and more costly, as well as susceptible to errors.


Federal Office of Topography swisstopo Seftigenstrasse 264
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3084 Wabern
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+41 58 469 01 11

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Geodesy and Federal Directorate of Cadastral Surveying
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Federal Office of Topography swisstopo

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