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 data base has now been built up. Here, a new mapping procedure has been used, which was developed in the context of a preliminary study in 2005, and implemented generally in 2006.
The following specialized information and geo-data, as well as satellite-image data, have been used:
Urban and Environmental Information System, Block Map 1: 5000 (ISU 5) and Land Use Data
The spatial reference of the 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. 23,000 sections of the ISU 5 structure, there is a 16-digit key, to which a database is linked. In this database, information on both section size and use is stored.
A total of 63 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 level of the ISU blocks and block segments.
- The ISU utilization data was used for the stratification of the municipal area, and were fed into the rule-based classification system.
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 August 2006, 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 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, buildings in industrial and commercial areas, and also summer homes in allotment-garden areas were frequently missed.
Map of Berlin 1 : 5000 – K5
The map of Berlin by the State Mapping Agency at a scale of 1 : 5000 (K5) has been 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.
Orthophotos
The full-coverage digital orthophotos used were taken from real-color aerial-photography material shot in August 2004. In the K5 sheet-line system, they are available in a resolution of 0.25 m, and were used for the following work steps:
- Geocoding of satellite photos,
- 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
For the ascertainment of correction factors for optimization of the evaluation procedure, the current impervious coverage information of the Berlin Water Utility (BWB) was consulted. 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.
The following restrictions had to be taken into account during the integration of the BWB data into the evaluation strategy:
- The BWB data were available only for properties with connection to the sewage system, particularly residential areas, not for all of Berlin.
- In traffic areas, parking lots, urban squares and promenades, green spaces, cemeteries, allotment gardens, areas with commercial or industrial use, areas with a low degree of built-up area, and supply and waste-disposal areas, the non-built-up impervious areas were often recorded only incompletely or not at all.
- The BWB definition of impervious coverage is different from that of the Environmental Atlas for some block types. While honeycomb-brick surfaces, or water-bound surfaces such as tamped ground and gravel surfaces are shown as 100% impervious in the Environmental Atlas, they are considered pervious in the BWB.
Multi-Spectral SPOT5 Scene
For the development of the procedure and the preparation of the impervious-coverage map, a multi-spectral SPOT5 scene (058/243) of September 5, 2005 was selected, and taken 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 could be used. 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.