C+S September 2020 Vol. 6 Issue 9 (web)

In 2018, Schiphol Airport in The Netherlands recorded 499,444 com - mercial air flight movements, an average of about 1,350 take-offs and landings per day. That quantity makes the airport an impressive third in busiest airports in Europe for passenger volumes, but it’s not a great statistic if you’re a geodata provider that needs to conduct an airborne survey near that crowded air space. Geospatial services company BSF Swissphoto knows a thing or two about that kind of air-traffic challenge. Since 2016, it has had to learn how to be nimble and flexible in order to successfully deliver on an annual aerial photo campaign north of the airport. “Roughly 85 planes are landing or taking off at Schiphol every hour, so flight control is incredibly strict,” says Sandra Beckmann, a project leader with BSF Swissphoto’s German office in Schönefeld. “When we are given a flight window, we have to be ready to go at a moment’s notice and we can’t afford any mistakes in collecting our photos be- cause it puts meeting our delivery deadline at risk. It’s an added level of complexity in a project that’s already challenging.” Indeed, in addition to working around potential weather delays and air traffic restrictions, the company has also had to meet unforgiving technical specifications and deadlines. They’ve had to produce homog - enous, seamless orthomosaics with a ground sample distance (GSD) of 4cm for a 900 square kilometer area of interest (AOI)–about the size of Madrid–in 11 weeks. However, Beckmann and her team have successfully shown that a smart flight plan and robust and efficient photogrammetry software are the right combination to navigate and land a complicated aerial survey and secure a route to repeat flights in the future. A routine exercise in coordination Flying the skies and photographing the ground underneath their wings has been at BSF Swissphoto’s core since it was first established in Switzerland in 1930. The company took on its first aerial survey and photogrammetry flight in 1960 and steadily grew its business by offer - ing multi-sensor solutions with millimeter accuracy. With a record for successfully delivering on surveying projects near Schiphol and other challenging areas around Europe, BSF Swissphoto was in a strong position to respond to the aerial photo needs of the Information & Coordination Centre (ICC) of the Schiphol Region. The ICC represents about 60 government-affiliated organizations, including 47 municipalities, and works to coordinate and provide access to up-to- date aerial photographs and other remote sensing products on a routine basis. Since 2009, it has issued tenders to capture high-resolution pho - tos of the 2800 sq km Region that extends from Alkmaar in the north, Repeated Imaging Success in Schiphol By Mary Jo Wagner

A shot of Amsterdam taken in flight.

Almere in the east and Zoetermeer in the south. Participating members use the detailed photos to update their large-scale topographic maps, for urban and environmental planning, for security and for monitoring land-use changes. Depending on the number of ICC participants, the program’s total AOI can change year on year, but the delivery requirements are always the same: orthomosaics with a ground sample distance (GSD) of 4cm or less. In 2016, BSF Swissphoto received a two-year contract to survey one of three AOIs under the ICC’s Vertical Aerial Photo program. Proving its capabilities, it was then awarded a subsequent contract for the same 900 sq km area for 2019 and 2020. “We are skilled in developing well crafted and realistic flight plans that not only enable us to be efficient in the air but also in processing the stacks of images we acquire,” says Beckmann. “Equally important is our ability to meet the exacting technical requirements. With Trimble’s Inpho® image processing software we have the tools we need to meet the orthophoto precision and the delivery timeline the project demands.” Collecting the aerial component For the 2019 campaign, BSF Swissphoto’s AOI included 17 ICC municipal territories in the northern part of Schiphol, each of which required its own seamless orthomosaic. In addition to the very high resolution specifications, the orthomosaic had to be precisely color- balanced – no dark shadows or excessively bright spots – geometrically accurate, completely clear with distinct contrast, and aesthetically pleasing. The aerial campaign began in February in order to acquire images of bare trees and to ensure they capture as much ground detail as possible. Considering the restrictive and complicated air traffic regulations, BSF Swissphoto split the whole AOI into seven sub-areas, delineating smaller fly zones near the airport and larger sections further north. The smaller sections were carefully chosen because the team knew they’d collect a significant volume of photos and they wanted to ensure the othophoto production would go as smoothly and efficiently as possible.


september 2020


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