Fascinating bird’s eye view

Aerial photographs and their scientific importance

  • Fotografie
13. Dezember 2018

What a revelation the first photographs of a place taken from the air must have been for the people who lived there! Until then – in the 18th and 19th centuries – only a handful of (wealthier) men and even fewer women had the time, courage and means to climb high mountains and see what the world looked like from above.

Walter Mittelholzer and the pioneers of aerial photography

After the invention of photography more or less in parallel by Frenchmen Joseph Nicéphore Niépce (1765–1833) in 1826 1 , Louis Daguerre (1787–1851) in 1839 2 and the Englishman William Henry Fox Talbot (1800–1877) in 1841 3 , it was only another 20 years before a photographer took a camera on a balloon trip. In 1858, the French photographer Nadar (1820–1910) 4 took the first aerial photograph of the Battle of Solferino from a tethered balloon; unfortunately, the picture has not survived. The American James Wallace Black took his first aerial photograph of Boston (Massachusetts) in 1860. In Switzerland, Eduard Spelterini (1852–1931) 5 , a balloonist from St. Gallen, made dozens of balloon trips between 1891 and 1893, upon which he photographed Swiss towns, landscapes and even the Alps. 6

With the outbreak of the First World War and the formation of air forces, aerial photography was used extensively for military reconnaissance purposes. In Switzerland, the St. Gallen photographer Walter Mittelholzer (1894–1937) particularly excelled in this field. After the war, Mittelholzer, who by then had also become a qualified commercial pilot, founded the company Aero-Gesellschaft Comte Mittelholzer & Co., which merged with another airline in 1920 to form Ad Astra Aero AG. In the early years, aerial photograph sales proved to be a more reliable business than the initially irregular flights with well-to-do passengers. They featured landscapes, places, factories, hotels and farms.Click to tweet The prints were sold individually to municipalities, factory owners, landlords, farmers, tourist offices and illustrated magazines. Mittelholzer chose the subject matter himself; gradually, however, he began to receive requests and commissions.

After Ad Astra Aero AG merged with Balair in 1931 to form Swissair, and Mittelholzer became Technical Director, he continued his aerial photography in the subsidiary Ad Astra Photo AG, which was renamed Swissair Photo AG in 1934. When Mittelholzer was killed in a mountaineering accident on 1937, the photographer Werner Friedli took the helm until 1960. Following the hiatus due to the Second World War, Swissair Photo AG continued to sell aerial photographs of municipalities and industrial businesses, founded a postcard printing house and published a book of photographs every couple of years. To this day, an aerial photograph of the municipality or one’s own house still hangs in many Swiss apartments, the majority of which stemming from Swissair or Air Color SA. 7

A photographic genre

Aerial images are photographic depictions of the earth from a bird’s-eye view or aircraft. From the First World War onwards, this kind of picture was used systematically for reconnaissance. Before long, however, scientists also discovered the technique for their own purposes. In cartography, aerial photography is still a key foundation in the production of map materials to this day.

A distinction is drawn between angled and vertical shots:

• angled aerial photographs serve as artistic, photographic views for architectural and landscape photographs for remote sensing;

• vertical aerial photographs are used to produce maps (cartography). 8

Often, aerial photography is regarded as a technical genre. As the photographs mechanically follow a clearly defined procedure, the photographer is not named.

Stephan Landtwing, member of the management board of the Swiss-German company BSF Swissphoto AG, explains how aerial photos are produced professionally today. The "successors of Walter Mittelholzer", as they call themselves, are active worldwide in the geodata industry with the three divisions 3D-Mapping, Engineering Surveying/Geo Monitoring and Consulting.

The large collection of historic aerial photographs in the Image Archive

With over 1.3 million aerial photographs, ETH Library’s Image Archive boasts the largest collection of historic aerial photographs in Switzerland.Click to tweet 9 By comparison: the Image Archive’s entire holdings currently total at around 3.5 million photographs (as of October 2018). The Collection of Aerial Photographs presently spans from 1918 to 2014 and predominantly comprises the following five large-scale holdings:

Walter MittelholzerPeriod: 1919–1937; Subjects: places, towns, landscapes, mountains, industrial buildings; Geography: all over Switzerland, Africa, Middle East; Volume: 14,500 angled shots, glass slides and plastic negatives, large format 13 x 18 cm, black and white; Companies: Ad Astra AG and Swissair; Digitisation/online publication: all images can be used online and free of charge. (Image: Le Locle at 100 m, approx. 1925, LBS_MH01-004655) 10 Holdings Walter Mittelholzer
Swissair Photo AGPeriod: 1937–2011; Subjects: places, towns, landscapes, mountains, industrial buildings, transport structures; Geography: all over Switzerland; Volume: 87,000 photographs, including 56,000 angled shots and 31,000 vertical shots, glass slides, plastic negatives and slides, large formats 13 x 18 cm to 23 x 23 cm, black and white and colour; Photographers: Werner Friedli, Joe Bischofberger, to name but a few; Digitisation/online publication: from quarter 2019 all can be used online and free of charge. (Image: McDonnell Douglas DC-10-30-30, HB-IHB "Schaffhausen" flying over Niesen, Lake Thun and Frutigen,1973-1984, LBS_SR04-055611)Holdings Swissair Photo AG
Comet Photo AGPeriod: 1957–1999; Subjects: mostly produced in connection with reports: places, towns, industrial buildings, transport structures; Geography: German-speaking Switzerland; Volume: 78,000 photographs, including 56,000 black and white and 22,000 colour angled shots, plastic negatives and slides, large format 13 x 18 cm; Photographers: not named; Digitisation/online publication: 18% are already online, digitisation in progress. (Image: National road N1/Motorway A1 in Buriet-Thal, junction Rheineck, 1962, Com_F62-00204) 11 Holdings Comet Photo AG
Aircolor SAPeriod: 1983-2014; Subjects: Single buildings (952,000) and places (95,000); Geography: all over Switzerland; Volume: 1.047 million colour angled shots, plastic negatives and digital photographs, medium format 6 x 9 cm; Photographers: not named; Digitisation/Online publication: being planned. (Image: Bremgarten (AG), 1985, AIC_02-0A-251050-005)
Desair AGPeriod: 1987-2014; Subjects: places, towns, landscapes, mountains, industrial buildings, transport structures, gravel quarries, recultivation projects; Geography: German-speaking Switzerland, Swiss Plateau, Jura; Volume: 90,500 colour angled shots, plastic negatives and slides, medium format 6 x 7 cm; Photographer: Heinz Leuenberger (one-man company); Digitisation/online publication: being planned. (Image: Zurich-Oerlikon, Oerliker Park, 2007, Des_07-66-001)

The archiving processes

Naturally, our users are unable to imagine much about library or archiving duties from outside. However, they are repeatedly astounded by how many images from a vast range of fields are available for download and free usage on the image database E-Pics Image Archive Online. One aspect in particular is worthy of mention: the archival preparation of print photographs is extremely time and resource-consuming, which is why it is performed highly systematically. By the end of this story, you will be capable of working out the workload yourself.

Accepting holdings

When accepting holdings, key preliminary decisions are made for all further work processes: what will be processed when and in what form? The prioritisation and degree of processing are thus defined based on the content-related focuses and the available (human) resources.


Student assistants remove the original packaging, usually plastic or pergamin covers, and pack the images in acid-free and padded paper suitable for archiving. In the process, they give both the photo carrier and the packaging material a clear location number. All metadata, i.e. any labelling on the photograph and the original packaging, is recorded in an Excel table. Fortunately, we have been receiving an increasing number of holdings with electronic metadata, which we tailor towards our database.


Digitisation is performed after the cataloguing phase in our own in-house DigiCenter. Again, it is predominantly student assistants who work here under the guidance of experts. They produce reproductions with the digital medium format camera Hasselblad H3D/H5D and scans using the Nikon Coolscan 5000 for small image formats. Due to user requirements – if someone needs to prove in court that the pergola on his or her house had not yet been created at a particular time point, for example – a printer resolution of A2 at 300 dpi has become the norm for aerial photographs. Other images are provided in A3 format.

The images are saved as 8-bit TIFFs in RGB. The image data is corrected as little as possible, whereby the workload is greater for colour photographs.


The image files and metadata lists are now imported into the image database. ETH Library’s Image Archive has been working with the digital asset management software “Cumulus” developed by the company Canto since 2005. During indexing, the photographs are labelled with the genre, location and, if need be, a subject heading.

Genre: Given the vast quantity of aerial photographs, the keyword “aerial photography” is divided into low and high-flying angled and vertical shots. As the altitude at which the photographs were taken is usually unknown, they are divided into “high” and “low” based on visual criteria, the most important of which being the visibility of windows on houses. Every photograph is systematically given only one genre keyword.

Place: Usually, we only issue one keyword for the first place named in the title, whether this be a political one (municipality) or a natural, geographical one (mountain, lake). The reason for this is also the vast quantity of aerial photographs. However, the note can already be prepared in the catalogue lists, which is less time-consuming than doing so directly on the database.

Subject title: If a building (e.g. a textiles factory) or a piece of infrastructure (e.g. a motorway) is the main subject of an aerial photograph, this is usually referenced.

All in all, it is safe to say that the archiving process for each photograph takes at least one hour! Now you can do the numbers: we have already uploaded 430,000 photographs...

Significance for research

So why go to all this trouble? One of the main duties of libraries and archives is to provide (culturally and historically valuable) documents and enable them to be used – for both academia and the public.Click to tweet For many years, aerial photographs have been the most used images in the Image Archive. Architects, urban planners, biologists and even private individuals use the aerial photographs for scientific assessments, planning work, court cases, hobbies or simply as a memento.

Professor Konrad Schindler, Professor of Photogrammetry and Remote Sensing at ETH Zurich, explains what researchers use historical aerial photographs for and how they produce their own aerial photographs for current research questions with little technical effort.

Maha Soltaniehha, doctoral student and research associate with a professorship for spatial development at ETH Zurich, reports on the advantages of aerial photography. Just as she needs them for the development and use of free spaces.

The crowd lends a hand

Do you know more about a photograph? Then send us your comments! Every image on E-Pics Image Archive Online has a feedback form in the image information (more information on this is also available in our Crowdsourcing Blog).

Geocoordinates are advantageous for many ways of using aerial photographs for academic purposes. However, the photographs in the Image Archive need to be georeferenced first. Since January 2018, interested members of the public have been able to georeference selected aerial photographs in a fun way on the platform sMapshot.

Viewing Earth from the air has become par for the course today: thanks to Google Maps, the latest aerial and satellite images can be accessed from virtually anywhere on the planet at any time. ETH Library’s Image Archive is archiving, indexing and digitising a culturally and historically important treasure trove of over 1.3 million aerial photographs documenting the development of Switzerland in the last 100 years from above.


  1. The very first photograph ↩︎
  2. Inventor of the daguerreotype ↩︎
  3. The first ever commercial book illustrated with photographs was originally published in six parts between 1844 and 1846. Talbot, William Henry Fox (2011): The pencil of nature [reprint] ed.. Chicago: KWS. ↩︎
  4. ↩︎
  5. Swiss National Library (2019). From above: Spelterini's balloon and the drone. Exhibition at the Swiss National Library in Bern, 28.2.-28.06.2019, https://www.nationalbibliothek.ch/de/archiv/von-oben-52.html. ↩︎
  6. From 1898 onwards, he also conducted flights over the Alps – including one with ETH Zurich professor Albert Heim. Heim, Albert; Maurer, Julius, & Spelterini, Eduard (1899): Die Fahrt der "Wega" über Alpen und Jura: 3 October 1898. Basel: Benno Schwabe, Verlagsbuchhandlung. ↩︎
  7. Weidmann, Ruedi & ETH-Bibliothek (2014): Swissair Luftbilder: das Luftbildarchiv der Swissair = Swissair aerial photographs: the Swissair Aerial Photography Archive. Zurich: Scheidegger & Spiess (Image Worlds No. 4). ↩︎
  8. https://de.wikipedia.org/wiki/Luftbildfotografie ↩︎
  9. The Collection of Historical Aerial Photographs at Swisstopo consists of around half a million, https://www.swisstopo.admin.ch/content/swisstopo-internet/de/topics/historical-images/aerial-photo/_jcr_content/contentPar/tabs/items/dokumente_publikatio/tabPar/downloadlist/downloadItems/428_1463568860400.download/Kennwerte-und-Merkmale_bf.pdf. ↩︎
  10. Surber, Kaspar & ETH-Bibliothek (2016): Walter Mittelholzer revisited: aus dem Fotoarchiv von Walter Mittelholzer = from the Walter Mittelholzer Photography Archive. Zurich: Scheidegger & Spiess (Image Worlds No. 6). ↩︎
  11. Albeit without the aerial photographs: Kreis, Georg & ETH-Bibliothek (2015): Fotomosaik Schweiz: das Archiv der Pressebildagentur Comet Photo AG = Photo mosaic Switzerland: the Archive of the Image Agency Comet Photo AG. Zurich: Scheidegger & Spiess (Image Worlds No. 5). ↩︎