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 acquire its aerial images. Based on Push-broom technology, this linear sensor scans a strip of the landscape while the aircraft moves and produces a single long image (up to more than 100 km). This technique requires fewer images than conventional frame cameras to cover the equivalent surface. The tedious work to stitch 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 Push-broom technology (green) and those acquired with a frame camera (in blue)

Each image strip is taken from three angles: at the nadir, forward and backward. These different angles of view allow us to get a three-dimensional model of the landscape and to measure the position and altitude of objects with great accuracy. This work, known as photogrammetric restitution, allows swisstopo to generate and update a large amount of data such as terrain models, 3D landscape models or national maps.

The 3 acquisition angles of the ADS100
The 3 acquisition angles of the ADS100

To ensure optimum coverage, images are taken with a lateral overlap of at least 30%. To guarantee the best possible quality of our products, from 2017 onwards, photographs will be acquired with a ground resolution of 10 cm on the Swiss Central Plateau, 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 cm.

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 acquire 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 flight takes place at approximately 2,400m above the ground to obtain a resolution of 10 cm and at about 6’000 m above the ground for a resolution of 25 cm.

Territorial division

swisstopo regularly flies over and photographs Switzerland and Liechtenstein. Since 2008, one third of the territory has been acquired every year according to a defined division. In force from 2017, the current breakdown divides the country into 3 regions according to cantonal boundaries.

  • The western region with 6 cantons (GE, VD, NE, FR, JU, VS)                          First acquisition in 2017
  • The central region with 10 cantons (BE, BL, BS, SO, AG, LU, OW, NW, UR, TI) First acquisition in 2018
  • The eastern region with 10 cantons (SH, ZH, TG, SG, AI, AR, SZ, GL, ZG, GR) and the Principality of Liechtenstein - First acquisition in 2019
     

Thanks to this division, communes and cantons always have complete data from the same flight year for their entire area.

Aerial imagery and derived products were divided up differently prior to 2017. The territory was also divided into three regions but did not follow administrative boundaries and thus did not offer the same advantages as the current distribution.

For the last 20 years, we have been improving the ground resolution of our images, going from 50 to 25 cm in 2005 and from 25 to 10 cm 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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