In accordance with the mapping units of the two actual-use maps of the Environmental Atlas, in particular the map “Inventory of Green and Open Spaces” (06.02), the open spaces that existed at the end of the Second World War were determined for the 1984/1985 version of this map, which was also its first version. The map covered the area of West Berlin and open spaces were determined based on old city plans, other maps and aerial photographs. Areas that were destroyed during the war and cleared later were not considered green and open spaces but rather built-up areas based on the historical context. This timeframe is referred to as “before 1945” in the present document. Open spaces that lay fallow for decades, for example at Potsdamer Platz, which were only developed again after the reunification of the city, were considered open space losses at the time they were built-up again.
Actual-use maps were superimposed on these green and open space maps in 1970 and 1980. The open space losses and gains were then copied out onto additional maps. Then, a balance was struck of the respective losses and gains, based on the area sizes. At that time, this was largely done on paper, at a scale of 1 : 50,000. The results were converted into digital form only later and were then based on the Environmental Atlas maps of actual land use, which have been continuously updated since 1985.
From then on, a change in land use was considered a loss of open space if the use changed from a category of the “Inventory of Green and Open Spaces” map to a use category included in the “Actual use of built-up areas” map. Green and open spaces are represented by the land use categories “Forest”, “Meadow and Pasture”, “Farmland”, “Park/ green space”, “City square/ promenade”, “Cemetery”, “Allotment garden”, “Fallow area”, “Sports use” and “Tree nursery/ horticulture” as defined in the “Inventory of Green and Open Spaces” (06.02) map of the Environmental Atlas. Areas assigned to construction use, e.g. public use areas, have also been categorised as open space, if they contain large contiguous and vegetated pervious areas (dual use, see SenStadtWohn 2021a). This has allowed the change in use since 1945 to be quantified for the periods indicated. It is important to note here that the open spaces presented in the “Inventory of Green and Open Spaces” Map (06.02) reflect all undeveloped land, as long as an area exceeds the 1-ha threshold and may therefore be recorded. The map thus shows land covered by vegetation rather than land use in terms of urban planning categories.
The open space losses refer to the time intervals specified above, while the open space gains refer to the entire period between 1945 and today. Areas that were built up within a certain time period (including road land) accompanied by a use change from a category of open space use to a category of construction use are presented as open space losses. This applies regardless of whether they were built up “before 1945”. This means that even areas that had been indicated as open space gains in previous versions of the map are later presented as losses, if they were built on again. Examples of this are the previously mentioned open spaces at Potsdamer Platz, which lay fallow for decades due to war and the Wall, as well as industrial sites that had been cleared and were then built on again after a few years, i.e. in a later decade. Gradual developments, such as the increasing development and densification of allotment gardens, accompanied by being recategorised as “Weekend cottage area”, are also recorded as open space losses, as the land use changed from a green and open space category to a construction use category here (cf. SenStadtWohn 2021a).
Areas that were developed before 1945 (without being destroyed during the war) and that were assigned to one of the above-mentioned open space categories in 2020 were recorded as open space gains. Demolition and the discontinuation of use (e.g. large railway facilities) due to the Second World War created open spaces, some of which were never built up again. They either still lie fallow and are often covered in vegetation or have been converted into public green and open spaces (e.g. parks at Gleisdreieck). In the end, only those areas that were developed “before 1945” were included as open space gains in the map.
In the early 2010s, the content of the map was already transferred from the digital block map 1 : 50,000 (ISU50, spatial reference Environmental Atlas 2005), which featured overdrawn roads for illustration purposes and which was not true to location, to the geometry of the block map 1 : 5,000 (ISU5, spatial reference Environmental Atlas 2010), which is true to location. This improved the usability of the map greatly and allowed for balances to be drawn up for the areas. At this time, the development process of the map also became more automated. The open space losses and gains were identified in a largely automated manner, now drawing exclusively on data from the actual use survey of the Urban and Environment Information System (ISU). Only a few manual checks were carried out based on aerial photographs or orthophotos. Areas with recorded open space losses and gains in the decades up until 2010 were adopted from the existing data base. For the current map, the open spaces losses and gains of the last decade, 2010-2020, were added to these. In this context, a first clear set of rules for generating the inventory of green and open spaces from the use categories of the ISU block (segment) area map was developed (cf. SenStadtWohn 2021). This makes it possible to create the inventory of green and open spaces largely automatically and based exclusively on the use data of the ISU block (segment) area map using straightforward criteria. This set of rules may be used for all future updates of the “open-space development” map. Accordingly, the definition of “open space” is now even more clear-cut than before, including all uses listed in Table 1 in the “Environmental Atlas” column under “open space”.
As part of developing the 2020 open-space development map update, the map was also divided into two different layers for the first time. This is the case as the geometry of the ISU5 block (segment) area map changed due to continuous geometric adjustments to the map as part of updates to the geometries of the loss/ gain areas and does no longer match that of previous periods. By dividing the map into two layers, it was possible to preserve both geometries, the current and the historical one, with their respective properties, and, to display them simultaneously by superimposing them on the open-space development map.
The two layers contain the following content:
- Layer 1: current inventory of green and open spaces and ISU block (segment) areas in the current geometry incl. attributes for each open space loss and gain time period. The attributes contain the area shares (percentages) of the respective period in the current ISU block (segment) area.
- Layer 2: original area geometries of the open space loss and gain areas from the each time period. An area can only ever be assigned to one category. Accordingly, ‘loss’ time periods may not overlap with one another within Layer 2.
With the map display, it is therefore possible, on the one hand, to identify the exact geometric boundaries of each loss and gain area (Layer 2). On the other hand, the attributes may be used to identify what percentages of an area are part of which loss and gain period for each current ISU block (segment) area. The workflow for creating the Open-Space Development Map 2020 was the following (cf. SenStadtWohn 2021):
- Generating the 2010 and 2020 inventories of green and open spaces based on the categories presented in Table 1.
- Merging the 2010 and 2020 inventories of green and open spaces to identify area differences between the two datasets, which represent the potential losses and gains of open space.
- Manually checking the potential areas of open space loss using the aerial photograph focussing on actual open space losses as compared to the previous time period.
- Manually checking the potential areas of open space gain using the aerial photograph focussing on actual open space gains as compared to “before 1945”.
- Creating Layer 2: merging the new loss and gain areas with the open space losses and gains from the previous time periods.
- Creating Layer 1: merging the gain and loss areas from all time periods with the current ISU block (segment) area geometry and calculating the percentages of the different categories for each ISU block (segment) area.
Generally, when considering an area at block (segment) level,* small-scale open space losses* that may occur within a block (e.g. due to retrospective densification) may not be recorded by the selected method. Areas measuring below 1 ha or the minimum width of 20 m were generally not recorded.