The swisstopo photographic collection boasts a unique cultural heritage, with some of its landscape shots dating back to the 1920s. With the aim of promoting this treasure trove and enabling the general public to benefit from it, “A journey through time – aerial images” allows users to view images in chronological order. It offers a simple and interactive way to embark on a remarkable journey through the history of Switzerland from a bird’s eye view.

Viewing A journey through time – aerial images

“A journey through time – aerial images” is incorporated into the federal geoportal map.geo.admin.ch using the “SWISSIMAGE Journey through time” layer. There are two ways to view the images:

The "Time travel - aerial images" contains images from 1946 to the present day. By processing thousands of aerial images, it is possible to travel through time for a selected location in Switzerland and thus observe the mutation of the urban environment and changes in the natural environment.

The images are in black and white until the end of the 90s. Colour then brought its reality to the landscape. Shooting technologies have also evolved. Today's shots show much more detail, such as pedestrian crossings on streets or solar panels on roofs.

Over the years, the area covered each year by images has gradually increased. Since 2005, digital data acquisition has also enabled faster image processing.

Off we go on a journey back through time !

In addition to the time travel, the whole of Switzerland is available with aerial images from 1946 from the "American flyover". This year is the only year in which the entire Swiss territory is shown in images. This visualization is not integrated in the Time Travel.

Discover Switzerland in 1946

In order to make aerial images available in map form, as in "time travel", the images must be processed into orthophotos. An orthophoto is an image that is free of distortions and has a uniform scale over its entire area. It can therefore be overlaid with other geodata and used as a basis for measuring coordinates, distances and are

"Time travel - aerial images" brings together different generations of orthophotos:

Black and White

For all years prior to 1997, the black and white aerial images that were used to update the national map at the time were used. In the end, some 108'000 images were processed. In a first step, the images are scanned and documented by entering metadata. Then, working in blocks, an automatic process is started to orientate the images according to control points on the ground (aerotriangulation). Once the orientation is done, the process continues with the orthorectification of the images which removes any optical and geometric distortion by correcting the image according to the camera calibration parameters and a digital terrain model.
The corrected images are then assembled into a mosaic, SWISSIMAGE HIST, to obtain the most homogeneous product possible.

The digitisation of the holdings started in 2010 and the work on generating orthophotos in 2017. 

Lucerne - 1971, 50cm, black and white (left). 2002, 50cm, colour (right).

Between 1998 and 2008, swisstopo's aerial images were converted to colour and the first SWISSIMAGE orthophoto mosaic was produced. The production process is similar to that of the black and white images, but manual interventions are carried out to optimise the image corrections (bridge deformation, optimal placement of the junction lines between the blocks, stretching of the pixels, etc.). The existing orthophotos were directly integrated into the time travel. To complete them, colour aerial images not yet ortho-rectified were processed in the same way as for the production of SWISSIMAGE HIST for the years 2005-2007.

Lucerne - 2002, 50cm, colour (left). 2006, 25cm, digital colour (right).

From 2005 swisstopo uses a digital camera for its aerial images. The ground resolution of the SWISSIMAGE mosaic is improved from 50 to 25 cm (in the lowlands). The planimetric accuracy also increases thanks to the new digital terrain models. From 2008 onwards, the production of orthophotos is switched from the LV03 coordinate system to the current LV95 system. In 2017, the introduction of the ADS100 digital camera, which is currently in use, further improves the ground resolution and planimetric accuracy.

Lucerne - 2006, 25cm, digital colour (left). 2021, 10cm, digital colours (right)