Data protection assessment of the use of aerial photographs for determining stormwater charges
The question of the data protection admissibility of using aerial photographs of private properties concerns authorities, property owners, and legal advisors alike. The background to this primarily involves the efforts of many municipalities to set wastewater charges based on causation, especially with regard to the costs associated with stormwater runoff. In a recent decision, the Düsseldorf Administrative Court addressed this issue and found such data collection compatible with data protection requirements (Decision dated 28 February 2024, Ref. 29 L 3128/24; Source: urteile.news).
Scope of application: Determination of charge-relevant property areas
Necessity of precise area determination
The purpose of using aerial photographs is generally to determine the sealed, that is, built or paved areas of a property, as these are crucial for the generation and drainage of stormwater. Precise area determination is necessary because the amount of the stormwater charge is linked to the proportion of sealed surfaces from which rainwater does not infiltrate the ground but is discharged into the public sewer system. The use of aerial images enables an objective and standardized collection of data, minimizing manipulation or inaccuracies compared to owner-provided information.
Legal bases and official practice
The collection and processing of personal data by public authorities in Germany is subject to data protection law, in particular the Federal Data Protection Act (BDSG) and the General Data Protection Regulation (GDPR). Specifically, in the municipal context, the municipal levy laws of the federal states also allow for such data to be collected if necessary for the fulfillment of duties—such as the levy of fees. The generation and analysis of aerial photographs by municipalities, therefore, constitute a data processing procedure that must withstand scrutiny under data protection law.
Data protection considerations and judicial assessment
Types of data and legitimacy for protection
Aerial photographs generally fall within the scope of personal data protection, as they allow conclusions to be drawn about ownership and the use of private properties. However, in practice, the data collected in this way is limited to information on property layout and surface sealing—not details of private life or residents’ behavior. According to prevailing opinion, the resulting encroachment on owners’ rights is considered proportionate and justified by the overriding public interest in a proper levy assessment.
Justification through the exercise of public duties
The collection of this data is limited to the municipality’s statutory duties and is used exclusively to determine the chargeable areas. It is thus carried out within the legal framework of Art. 6(1)(e) GDPR in conjunction with the relevant state law provisions. The court emphasized in its decision that there is neither a violation of data protection regulations nor an unreasonable impairment of the affected owners. In particular, the objective limitation of data usage and the absence of publication or further dissemination of the information sufficiently meet the principle of data minimization.
Proportionality review and protective measures
As part of the proportionality review, it should be noted that the production and analysis of aerial photographs is a moderate means to achieve the authority’s objective. The collection of additional sensitive information does not typically occur. The handling and storage of the data are further subject to significant legal protection mechanisms and organizational safeguards against unauthorized access. From the court’s perspective, there is therefore no reason to doubt the data protection compliance of this approach—as long as processing is strictly limited to its intended purpose and conducted properly.
Impact on property owners and municipal practice
The decision has far-reaching consequences for the practice of municipal fee assessments. It signals that authorities may utilize modern technical means to ensure that the determination of the tax base is as fair and transparent as possible. This also allows for conflicts over the accuracy of the assessment basis to be largely avoided.
At the same time, the decision clarifies that data protection concerns are particularly dispelled when the authority can demonstrate that data is collected and used exclusively for the legally prescribed exercise of duties. In this respect, property owners generally have rights to information and objection, but the extent of these rights may be limited by the overriding public interest.
Summary and outlook
According to current administrative court case law, the use of aerial photographs for the purpose of calculating stormwater charges meets the requirements of data protection law, provided that data collection and processing are purpose-bound, proportionate, and lawful. The decision of the Düsseldorf Administrative Court in this context sets important standards for the structuring of fee practices and strengthens the use of modern information technology in administrative processes, without neglecting the rights of property owners.
For further information on data protection issues and the legal structuring of administrative procedures, the lawyers at MTR Legal will be happy to assist you.
