Green Roofs 2020

Statistical Base

Multispectral remote sensing data is particularly suitable for capturing green roofs. The “view from above” allows a spectral differentiation of roof surfaces and materials. Essential data that was needed for an accurate classification was available in the form of current, high-resolution, digital colour-infrared orthophotos and elevation data, as well as building and roof outlines.

The following information formed the statistical base:

  • Digital colour infrared TrueOrthophotos 2016 (TrueDOP20CIR) and a normalised Digital Surface Model (nDSM), aerial photography flights on August 1, 8, 12, and 16, 2020 (SenSW 2020a)
  • Building geometries as well as underground car parks of the Official Real Estate Cadastre Information System (ALKIS) as of May 2022 (SenSBW 2022),
  • NOT-ALKIS buildings: freestanding buildings, as of 2021
  • Urban and Environmental Information System (ISU5) – spatial reference and land use data, as of December 31, 2020 (SenSW 2020b)

In order to avoid overlaps with ‘building areas’, only such underground car park area shares without superstructures were used of the ‘underground car park areas’ listed in ALKIS.

In addition to the ALKIS building dataset, a classification of the 2020 nDSM was carried out, facilitating the development of a NOT-ALKIS building dataset (SenSW 2020b, SenSW 2021a). The buildings thus determined were used to supplement the building data basis for selected area types (single-family homes, row houses and duplexes, villas, allotment gardens, weekend cottages and rental-flat buildings of the 1990s and later). Any freestanding NOT-ALKIS buildings on these areas were selected for the data basis in addition, to facilitate a statistical evaluation by building. Any NOT-ALKIS building parts that merely supplement an ALKIS ‘building area’ could therefore not be included.

The ‘building’ data base (ALKIS and NOT-ALKIS buildings combined) comprises a total of 629,666 objects. It should be noted that about 105,000 of these buildings represent very small objects of less than 20 m² (e.g. garages or allotment garden huts).