Geodata is digital information that can be assigned a specific spatial position on the earth's surface (geographic information , georeferencing ). They can be directly obtained primary data or further processed secondary data . Metadata , which describe the actual spatial data, for example with regard to a time reference or its origin, are of particular importance for geodata . Spatial data is divided into spatial data producing spatial references (in Germany referred to as " geospatial base data ", in Switzerland as "georeferential data "), which are usually provided by the surveying administrations of the federal states or municipalities (in Switzerland by the responsible offices of official surveying) and in geospatial data that originate from various spatial specialist databases. They are in a geographic information system out that by an Internet-based systems for geobrowser can be tapped.
A widespread object modeling in geographic information systems (GIS) is to store such objects on the one hand with their geometric shape ( English shape ) and on the other hand with the associated factual information ( attributes ). The latter can also refer to the geometric object with a reference . In theory, there is no limit to the dimensions of the geometric shape. The time is often used as a dimension, such as measurements or remote sensing data of different time points.
Before the start of the digital era (before 1970), geodata were recorded in analog form: on map drawings and sketches, in notes and later on index cards, and before the era of map printing (15th century linocut) in hand-painted individual maps.
Modeling of geospatial data
As a rule, a distinction is made between the geometric shape primitives point , line and surface. Areas are often only modeled as a polygon . However, this is not enough in demanding applications; Curvilinear area boundaries are necessary here and areas with holes ( enclaves ) as well as areas with spatially separated parts ( exclaves ) can occur. Since the end of the 20th century, efforts have been made to model geodata according to international norms and standards . In the ISO 191xx set of standards of the International Organization for Standardization, there is the ISO 19107 Geographic Information - Spatial Schema standard , which standardizes precisely this area.
- two-dimensional 2D
- Each point has an x and a y coordinate . Line connections or areas that build on the points are therefore in one plane ( xy plane ). This corresponds to the normal map display and data management in the cadastre .
- two-plus-one-dimensional 2 + 1D
- Each object also has attributive information about the height (for example a building height on the building). This form can be found in some cadastral data.
- two and a half dimensional 2.5D
- Each point in the plan view has a height in addition to the x and y coordinates. However, this means that the height is only a function of the position; In other words, there is only ever exactly one height value for a position coordinate (x, y). Most digital terrain models are available in this form . Vertical walls and overhangs cannot be modeled in this way.
- three-dimensional 3D
- All points have x, y and z coordinates (or height). Line connections are spatial lines that do not lie in one plane. If circular arcs occur as connections, these are, strictly speaking, elliptical sections that lie in an inclined plane; or they have to be approximated by lines with correspondingly short segments. Surface objects are only flat surfaces if they are delimited by exactly three points, otherwise they are curved spatial surfaces.
- four-dimensional 4D
- In addition to the three coordinates in space, the time is recorded as the fourth piece of information resulting from the chronological sequence. This is made possible, for example, by using a time stamp for each object. This can be used to query at what point in time an object existed or not. From this data, representations of the past can then be created (for example: What did the site look like on February 15, 2002, before the new building was erected); time-dependent animations can also be generated (for example the progress of coal mining in a mine). It is also possible to display time-related geodata (time series) as a journey through time .
Even if the objects only have two-dimensional shapes, they can be embedded in the three-dimensional or two-dimensional space. For example, this means that three coordinates (x, y, z) or two coordinates (x, y) are stored for a point.
In addition to the geometry (shape, size and position) of the objects, the topological relationships of the objects are also modeled. The topological basic forms node, edge and mesh are used for this. In simple systems, the points correspond to the nodes, the lines to the edges and the surfaces to the meshes. The explicit modeling of the topology can be dispensed with if it can be derived from the geometric data. This is the case with simple systems when the geometric data is available in three dimensions. Two-dimensional geometries are generally not sufficient to derive a topology; A level crossing and a level-separated crossing (bridge) are topologically different, for example, but cannot be distinguished from one another in the two-dimensional geometry.
Quality of geospatial data
The quality of data can only be assessed on the basis of the quality characteristics with regard to a specific question. The amount of data features that enable the use of the data for a specific task can be referred to as data quality. These data characteristics should be documented in the corresponding metadata . The quality parameters of the ISO standard ISO 19113 are:
Completeness ( complete ness )
Presence or absence of objects, their attributes and relationships:
- Excess data ( commission ): Data record has additional information
- Lack of data ( omission ): The data set contains less data than specified
Logical consistency ( logical consistency )
Compliance with logical rules of the conceptual, logical and physical data structure:
- Conceptual consistency ( conceptual consistency ): compliance with the conceptual schema such. B. for updates
- Values consistency ( domain consistency ): Compliance with the value range, for example, negative values for a population mapping
- Format consistency : Correspondence of the data record with the physical data structure
- Topological consistency ( topological consistency ): accuracy of the encoded topological characteristics such. B. Neighborhood relationships must be maintained
- Geometric consistency ( geometrical consistency ): To what extent is the same the spatial data set with the geometric conditions of the corresponding specification for. B. no double digitization points
Position accuracy ( positional accuracy )
Accuracy of the position of objects:
- Absolute or external accuracy : Agreement of determined coordinate values with true coordinate values
- Relative (inner) precision ( relative accuracy or internal ): According relative positions of objects to one another with true relative positions
- Raster data accuracy ( gridded data position accuracy ): Consistency of raster data position values with true values
Accuracy in time ( temporal accuracy )
Accuracy of the times and the temporal relationships of objects:
- Accuracy of a time measurement : Information on a data record about the accuracy of the time information, e.g. B. to the minute, to the day
- Consistency over time ( temporal consistency ): accuracy of temporal events and sequences such. B. Order of land use
- Validity time ( temporal validity ): To what extent is true, the data set in terms of the required time, for. B. Time specification of the type: year-month-day
Thematic accuracy ( thematic accuracy )
Accuracy of quantitative attributes and of non-quantitative attributes - assignment of objects to object classes and correctness of the relationships:
- Correctness of the classification ( classification correctness ): Voices objects or their attributes and their assigned classes agree to such. B. Assignment to river instead of route
- Correctness of non-quantitative attributes ( non-quantitative attribute correctness ): e.g. B. Type of land use
- Accuracy of quantitative attributes ( quantitative attribute correctness ): e.g. B. Area of land
Legal framework for geospatial data
Before GDPR, May 2018 (and therefore out of date): Whether and when geodata that is freely or generally accessible to government agencies can collide with data protection for personal data is still largely unclear in Germany. Initial efforts to shed more light on the subject of spatial data and data protection were made by the Commission for Geographic Information Management. These and the Federal Ministry of Economics commissioned studies from the Independent State Center for Data Protection Schleswig-Holstein . The latter came to the result in the study published in September 2008 that at present both the interests of those interested in a use, as well as the data protection issues, cannot be adequately balanced with the existing legal regulations. In particular, the INSPIRE process, which has also been initiated at the EU level, requires modern spatial data law, which is also not created with the federal and state spatial data access laws (e.g. the spatial data infrastructure law that came into force in Bavaria on August 1, 2008). Rather, these laws fall back on traditional access regulations and do not react to the new challenges for the use of spatial data and the protection of the personal rights of individuals.
With GDPR, May 2018: The legal basis for the use of spatial data has changed with effect of the GDPR from May 2018. Initial statements can be summarized as follows: It should be noted whether the geodata is information about a natural person or not (e.g. position of a person or building height). Even if non-personal geographic information, such as the height of a building, can be related to a person through the geo-reference, the geographic information, here building, continues to be non-personal information. A first detailed, legal statement was made by attorney Schmidt. From a technology-sociological point of view, see also the study Current Issues of Geodata Use on Mobile Devices by the Institute for Technology Assessment of the Austrian Academy of Sciences (ITA / ÖAW).
Since spatial data can also affect state security interests, corresponding legal restrictions on free access are planned.
In Germany, the Geodata Access Act (Act on Access to Digital Geodata - GeoZG) came into force in 2009. The law serves to set up a national spatial data infrastructure. It creates the legal framework for access to spatial data, spatial data services and metadata from agencies that hold spatial data (“agencies of the federal government and of federal legal entities under public law”) as well as the use of these data and services, in particular for measures that have an impact on the environment can have. The federal government has been providing geodata free of charge since 2012. The ordinance (GeoNutzV) announced on March 22, 2013 grants extensive rights of use (reproduction, processing, presentation, integration into products) provided that the attached source note and legal information are clearly integrated in the visual context and, if necessary, provided with a notice of change becomes.
In Switzerland, access to basic geospatial data (in the sense of the Swiss term basic geospatial data ) is largely regulated by the Federal Act on Geoinformation (Geoinformation Act, GeoIG, SR 510.62), to which the cantons have subscribed with supplementary executive decrees. Here, the basic geospatial data according to federal law (as well as by the cantons in their legislative area) are listed in a catalog of the basic geospatial data and made transparent with their legal attributes, whereby the access authorization is also explicitly regulated here. With this regulation of access authorization to geospatial reference data (according to GeoIG Art. 10–15), the handling of data protection could be dealt with largely legally.
Examples of geospatial data
- Data from ATKIS
- Digital Chart of the World (DCW), replaced by VMAP data
- GTOPO30 elevation data
- SRTM data
- Landsat raster images
- Data of the standard-based exchange interface
- Google Maps
- Mario Martini , Matthias Damm: On the way to Open Government: Regime change in spatial data law . German Administrative Gazette 2013, Issue 1, pp. 1–9.
- opengeodb.de - Free geo-coordinate database for MySQL, PHP class
- Geodata Germany - geographic coordinates of all 1.2 million streets with postcodes, places and districts
- www.GEOcatalog.de - GEOcatalog of the Center for Geoinformation
- "Geodata are not personal, but factual." Free report from the Institute for Legal Informatics at the University of Hanover, March 2009
- "Coordinating demographic change through geodata: researchers from the Anhalt University of Applied Sciences support municipalities with structural changes" , article on the scientific use of geodata
- Geoportal.de, a service provided by the federal, state and local governments
- GeoInfoMarkt.org, a service especially for business
- Basics of data quality . Christian Müllegger, University of Vienna. Accessed on May 3, 2009. ( Page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.
- Rothmann, Robert; Sterbik-Lamina, Jaro; Peissl, Walter; Čas, Johann: Current issues regarding the use of geodata on mobile devices. In: Report no. ITA-PB A63. Institute for Technology Assessment (ITA): Vienna; on behalf of: Austrian Federal Chamber of Labor., 2012, accessed on March 1, 2019 .
- Federal Law Gazette 2013 I No. 14
- Federal Act of October 5, 2007 on Geoinformation , accessed on April 19, 2019.