Data on impervious soil coverage for Berlin have been available in the Environmental Atlas since the beginning of the ‘80s. At first, this was true only for the western part of the city; since the political change in the East, a full-coverage data stock has been built up and maintained over the course of a number of shifts of emphasis and updates. However, this data base was no longer up-to-date, and was moreover based on non-uniform surveying methods.
In cooperation with the Berlin University of Technology, the Humboldt University and the company Digitale Dienste Berlin, a new procedure for ascertaining impervious coverage was developed for the 2007 Edition. It is now been partially re-adapted and used for the 2012 Edition. The databases for impervious coverage which had existed previously had been based on non-uniform ascertainment methods, for which reason a direct comparison was not possible. The present reuse of this ascertainment method now permits an overall comparison of degrees of impervious coverage between 2005 in 2011.
The following specialized information and geo-data, as well as satellite-image data, have been used:
The Urban and Environmental Information System, Block Map 1: 5,000 (ISU 5) and Land Use Data
The spatial reference of the City and Environment Information System (ISU) is oriented toward the structure of the statistical blocks of the Regional Reference System (RBS) of the Berlin-Brandenburg Bureau of Statistics. However, each block may be further subdivided into homogeneous-use block segments. For each of the approx. 25,000 sections of the ISU 5 structure, a 16-digit key is stored in a database, in which information on both section size and use is stored.
A total of 52 section types with homogeneous use and spatial structures are distinguished. The ISU 5 was used for the impervious coverage maps current as of Dec. 31, 2005. The ISU data were used as follows in the evaluation process:
- The geometric data served to delimit blocks and distinguish streets and bodies of water. Sections outside the statistical blocks were not analyzed.
- The degrees of impervious coverage were calculated at the ISU block and block segment levels.
- The ISU utilization data were used for the stratification of the municipal area, and were fed into the rule-based classification system.
In the course of the updating of the database in 2010, not only were the block geometries further developed, but the categories and the information on land use and urban structure were also revised. In this process, changes in the mapping methodology, e.g., the definition of section types, were undertaken, which had implications for the impervious coverage mapping methodology developed for the Database 2005. For the impervious coverage investigation in 2011, it was therefore necessary to undertake certain procedural modifications.
Automated Map of Properties (ALK)
In Berlin, the lot-referenced factual and geometric data of the Register of Land Properties is maintained in the form of the Automated Book of Properties (ALB) and Automated Map of Properties (ALK). The data stock of the Berlin ALK covers the entire area of the State of Berlin and consists of approx. 1.5 million properties, largely fields and buildings.
The vector data of the ALK, current as of December 2010, were used for the delimitation of buildings within the ISU blocks, and for the specification of remaining areas as non-built-up block space, and hence as analysis areas for satellite-image evaluation.
With regard to the integration of the ALK data into the evaluation process, it was ascertained that facilities on railyards and urban-rail stations, and also buildings in industrial and commercial areas, were frequently missed. Due to a change in the definition of buildings, summer cottages in allotment-garden areas are no longer included in the current ALK.
Map of Berlin 1:5,000 – K5
The map of Berlin by the State Mapping Agency at a scale of 1:5,000 (K5) is drafted by the Berlin boroughs on the basis the Berlin ALK. The above-ground railway lines shown in the K5 Map were used for the impervious-coverage maps current as of January 2006, to the extent that these were provided by the boroughs. The lot-precise recording of track beds was used primarily for the mapping of the shaded railway lines in forests, such as that north of Müggel Lake.
The full-coverage digital orthophotos used were taken from real-colour aerial-photography material shot in July and August 2010. In the K5 sheet-line system, they are available in a resolution of 0.25 m, and were used for the following work steps:
- Ascertainment and delimitation of reference sections,
- Ascertainment and delimitation of sections to be corrected (e.g. water bodies not recorded).
Data on Impervious Soil Coverage of the Berlin Water Utility
In the process of the evaluation, so-called corrective factors for ascertaining the degree of impervious coverage were used for certain section types. The purpose was to correct the view from the air, in which the impervious coverage is often largely obscured by trees, with certified information on impervious coverage. The corrective factors developed and tested in 2007 were used again. The ascertainment of corrective factors was carried out on the basis of the current impervious coverage information of the Berlin Water Utility (BWB). Starting in January 2000, these data were collected in connection with the changed calculation of the precipitate-water fees. The BWB aerial photography and the ALK served for the initial recording of the impervious sections of the properties. Moreover, the checked information of the property owners was incorporated (WTE 2004). The lot-precise data was aggregated at the ISU block-segment level, and was available for evaluation, current as of 2001. Only the details on the non-built-up impervious sections were used. Lot-precise local observation and recording permitted a very high degree of precision of data on impervious soil coverage to be obtained.
Multi-Spectral SPOT5 Scene
In 2011, the state of Berlin issued a contract for the photography of a SPOT5 scene. For the development of the procedure and the preparation of the impervious-coverage map, it was ultimately possible to use a multi-spectral SPOT5 scene of May 8, 2011 as a system-corrected data set. The photo was free of clouds. The analysis of the spectral bands showed only very low atmospheric impairment. The pan angle was approx. 1.9°, and tilts of buildings were negligibly low, so that in the context of this project, an “ideal” scene was available. Due to the seasonal lighting conditions, the shaded areas were relatively large; however, they were in any case treated separately in the development of the procedure.