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Switzerland in high resolution

As the main input for the production of geodata, aerial images are the basis for products such as SWISSIMAGE or national maps. Thanks to a state-of-the-art photo sensor, swisstopo brings you Switzerland in high resolution.

At swisstopo, we have been photographing Switzerland from above since the mid-1920s. Several changes in equipment have made it possible to follow the technological evolution from black and white to colour, to add infrared information or to increase ground resolution. In 2005, the acquisition of aerial images entered the digital age.  

State-of-the-art airborne technology

Swisstopo uses a Leica Geosystems ADS100 camera to record its aerial images. Based on the push-broom method, this linear sensor scans a strip of the landscape while the aircraft moves and produces a single long image (covering a distance of more than 100 kilometres). This method requires fewer images than conventional frame cameras for covering the equivalent surface area. This means that the need to join images together is thus reduced to a minimum.

Footprint of images acquired using Push-broom technology (green) and those acquired with a frame camera (in blue)
Footprint of images acquired using the push-broom method (green) and those acquired with a frame camera (in blue)

Each image strip is taken from three angles: directly from above, to the front and to the rear. These different angles of view enable us to produce a three-dimensional model of the landscape and measure the position and altitude of objects with great accuracy. This process is referred to as photogrammetric restitution. It allows swisstopo to generate and update a large amount of data, such as terrain models, 3D landscape models and national maps.

The 3 acquisition angles of the ADS100
The 3 angles recorded by the ADS100 camera

To ensure optimum coverage, images are recorded with a lateral overlap of at least 30 percent. To guarantee the best possible quality of our products, from 2017 onwards all photographs will be taken with a ground resolution of 10 centimetres on the Swiss central plateau, in the Jura and in the two main Alpine valleys (the Rhone downstream from Brig and the Rhine downstream from Chur). With significant differences in altitude, the more complex topography of the Alps limits this ground resolution to 25 centimetres.

Longitudinal (blue) and lateral overlap (green) of the ADS100
Longitudinal (blue) and lateral overlap (green) of the ADS100

Distribution of ground resolutions: 10 cm (blue) and 25 cm (green) - subject to change

Distribution of ground resolutions before 2017: 25 cm (in light green) and 50 cm (in dark green)

To obtain these images, the aircraft flies over Switzerland from west to east or follows the axis of the valleys whenever the topography does not allow this. The aircraft flies at an altitude of around 2,400 metres above the ground in order to produce a resolution of 10 centimetres, and at around 6,000 metres above the ground for a resolution of 25 centimetres.

Photography by region

swisstopo periodically flies over and photographs Switzerland and Liechtenstein. Since 2008, one-third of the territory has been photographed each year according to a defined regional division. As of 2017, the country has been divided into 3 regions based on cantonal boundaries.

  • Western region (6 cantons: GE, VD, NE, FR, JU, VS) - Initial recording 2017
  • Central region (10 cantons: BE, BL, BS, SO, AG, LU, OW, NW, UR, TI) - Initial recording planned for 2018
  • Eastern region (10 cantons: SH, ZH, TG, SG, AI, AR, SZ, GL, ZG, GR) and the Principality of Liechtenstein - Initial recording planned for 2019
     

Thanks to this regional division, municipalities and cantons are always in possession of complete data from the same flight year for their entire sovereign territory.

Aerial imagery and derived products were based on a different regional division prior to 2017. The country was also divided into three regions, but the division was not based on administrative boundaries and thus did not offer the same advantages as the current solution.

For the past 20 years we have been improving the ground resolution of our images, from 50 to 25 centimetres in 2005 and from 25 to 10 centimetres in 2017 (a 25-fold increase!).

Orthophotos samples with a ground resolution of 10 cm (left) and 25 cm (right)

Orthophotos samples with a ground resolution of 25 cm (left) and 50 cm (right)


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

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Federal Office of Topography swisstopo

Seftigenstrasse 264
P.O. Box
3084 Wabern

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