In 1992/93, the first state-wide color infrared (CIR) aerial survey took place in the state of Saxony-Anhalt. Based on the analogue aerial photographs, a biotope type and use type (BTNT) mapping was created, the results of which are available in digital form (as ESRI coverage).
During a second nationwide CIR flight in 2005, precise high-resolution (20 cm pixel size) digital CIR orthophotos were taken. On this basis, the BTNT mapping of 1992/93 could be corrected and updated. The results of the BTNT update are also available as ESRI coverage. A further update was made on the basis of aerial photographs taken in 2009.
This database (BTNT as of 2009) is to be updated on the basis of the CIR partial flights of the years 2021 and 2022 in order to be able to take stock of developments in the landscape in the course of monitoring. Of particular interest are the changes in the area of the NATURA 2000 area setting.
Some of the CIR orthophotos for 2021/22 show an unfavourable flight period (April-June) as well as extensive drought damage in forests. These aggravating conditions place the highest demands on the qualifications, experience and knowledge of the processors.
The processing is carried out nationwide for Saxony-Anhalt.
1. Update of the biotope type and use type mapping
1.1 Initial data
The initial data for the interpretation are the results of the update of the BTNT mapping based on the 2009 national survey. The data is available as an ArcInfo coverage library, where areas and lines are stored redundancy-free in a common net coverage, points separately in a point coverage. This redundancy-free, integrative, sheet-cut-free and consistent data structure must be maintained throughout the entire machining process.
The CIR aerial photographs used in 2009 had an image resolution of 40 cm and are therefore of much lower quality than the CIR aerial photographs from the 2021/22 national survey. Their interpretation, in turn, is made more difficult by the time of flight and forest damage. The detection of changes compared to 2009 thus places very high demands on the experience of potential performers in dealing with digital CIR image material and requires very good regional knowledge in Saxony-Anhalt. The following restrictions must be observed:
- The recognition of tree species is partly no longer given, deciduous forest stands are still partly leafless and can only be recognized with restrictions by the trunk shade, coniferous forest stands are clearly recognizable.
- Bodies of water and buildings are clearly visible.
- Herbaceous vegetation units have their own peculiarities, some of which differ significantly from the 2009 aerial photographs, but allow a change detection.
- Due to the drought years, water bodies have dried up. River floodplains, especially the Elbe floodplains, have low water. The exposed mud banks or siltation zones are to be mapped out.
- The positional accuracy of the 2009 digital aerial photograph set differs in part from the 2021/22 aerial photographs, position adjustments are only to be made in the event of real changes.
- The best interpretation results can be obtained from a direct comparison of the two sets of aerial photographs.
- In case of doubt (poor recognizability), the status quo is maintained, so that no changes are interpreted.
1.2 Methodology of the update
1.2.1 Processing
For the interpretation, the use of the "Catalogue of biotope types and use types for CIR aerial image-based biotope type and use type mapping in the state of Saxony-Anhalt" (see appendix) is mandatory.
The evaluation of the digital data is to be carried out on the screen and represents an update of the digital biotope type and usage type recording from the 2009 survey (pure change detection). Only real changes, such as those caused by human activities, succession processes or others, should be recorded. The freedom of interpretation is limited to the extent that only real changes are to be interpreted in terms of content. In addition, only obvious, significant errors in the pre-mapping should be marked and corrected separately by the interpreter. Experienced aerial interpreters with regional knowledge are to be used to determine the changes. The experience of the performers must be proven by references.
Interpretation, including changes to codes and geometries, must be performed using ArcInfo Workstation (ArcEdit). An AML application created for the specific work task is provided by the client. Working on two-monitor systems with parallel ArcGIS installation is recommended.
1.2.2. Error definition/control
The revised interpretation service shall be deemed to be usable within the meaning of the contract to be concluded if an error rate of 3% for gross/significant errors or 15% for less significant errors according to the following definition is not exceeded. The variety of features of the catalogue is to be fully exploited. The following error definition takes into account ecologically relevant structures in particular, since their exact mapping is a basic prerequisite for further processing of the results.
Gross/significant errors are, for example:
- General omission of structures larger than the area trap (0.25 ha area or 100 m line). Experience has shown that this applies to field shrubs and hedgerows, differentiable units in the forest, woody plants along traffic routes and rivers and small-scale wetlands.
- Failure to observe the exception of the area trap. "Woody plants", "bodies of water", "built-up areas" in the open landscape must always be mapped. If the structures mentioned are smaller than 0.25 ha or shorter than 100 m, they must be mapped as a point (see catalogue, p. 4).
- Unlabeled objects.
- Indication of incorrect encodings that are not possible according to the catalogue.
- Non-specification/omission of additional information clearly recognizable in the aerial photograph, e.g. degree of bush encroachment, degree of sealing.
- failure to specify the mapping unit (feature) and structural unit (SE); Exception: W... f.
- Swapping the object names (e.g. settlement receives coding for forest).
- Significant deviations of the demarcation of biotope types and types of use from the (clearly) aerial boundaries (e.g. forest edges, agricultural land, excavations, etc.).
- Interpretation errors such as:
Confusion of the mapping unit (e.g. riparian forest as mixed deciduous forest)
Confusion of deciduous and coniferous shrubs
Bodies of water that are clearly anthropogenically impaired or designed are interpreted as near-natural
Misjudgement of age groups by two levels and more
Less significant errors include:
- Failure to specify fringes "Herbaceous vegetation" along flowing waters.
- Misinterpretations such as misjudging the age groups by one level.
In order to be able to implement the client's requirements exactly, a consultation appointment at the client's registered office is required before the start of the work.
1.2.3. Systematic processing
The processing of the data is carried out in sections (tiles) of 2x2 km in size.
The data must be processed successively in such a way that there are no geometric, topological and content-related breaks between adjacent tiles and that the entire area is processed in uniform quality. The methodology of creating editing sections from the ArcInfo library and inserting edited tiles is specified by the client as follows: The tile to be edited with its neighbors (i.e. a total area of 6x6 km) is to be extracted from the library. The surrounding tiles are locked for editing. The tile to be edited is completely edited, including the geometries on the edge of the tile. The rest of the content of the neighboring tiles remains unaffected. The reinsertion of the edited tile takes place topologically exactly at the unchanged boundaries of the neighboring tiles. Once reinserted, the adjacent tiles can be unlocked. For this purpose, the library is to be managed as a "transactional library".
1.2.4. Data to be provided
The contractor provides the results of the 2022 interpretation in the form of an ArcInfo library.
The contractor successively hands over the updated data to the client, who checks it comprehensively before acceptance. The contractor receives the data processed by him back together with an error analysis of the client to improve the quality of his further work or, in the case of qualitative defects, for post-processing.
1.2.5. Quality criteria
The data described in 2.1.1.2.2. the error rate referred to above must not be exceeded.
The result record must have a healthy topology.
1.2.6. Documentation
Upon completion of the work, the contractor shall provide documentation of his approach and the results obtained.
1.3. Organisation and coordination
1.3.1. Leistungszeitraum
The service must be paid in the period from July 2023 to November 2024. Optionally, a service that is not yet to be commissioned here is possible until 2025.
1.3.2. Coordination
By coordinating, the contractor shall ensure that the data collected is subject to a uniform quality management system and is handed over to the client in a homogeneous form.
1.3.3. Erörterungstermine
In order to be able to implement the client's requirements exactly, a consultation appointment at the client's registered office is required before the start of the work.
If necessary for the qualification of the work, further discussion dates may be set by the client. These are part of the offer.
1.4. Terms and Conditions of Contract
1.4.1. Service offerings
The service is awarded to only one bidder, who may involve subcontractors. The subcontractors are to be announced with the submission of the offer with name and address. The service includes the updating of the biotope type and use type interpretation as well as the associated coordination tasks.
1.4.2. Services provided by the client
The following are provided by the client:
- Data of the biotope type and use type interpretation from 2009 as ArcInfo library
- Catalogue of biotope types and use types for CIR aerial photo-based biotope type and use type mapping in the state of Saxony-Anhalt" (Reports of the State Office for Environmental Protection Saxony-Anhalt, issue 4/1992) as a binding regulation for interpretation
- AML application for computer-aided updating
- digital CIR aerial photographs of the 2009 (40 cm resolution) and 2021/22 (20 cm resolution) flights.