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What are geodata?
What does georeferencing mean?
What distinguishes vector data from raster data?
In a short overview some of the basic terms are explained and hints are given for the application of geodata.
Contents: Geodata   -  Contents and Importance
  Basic Geodata   -  an overview

Geodata - Contents and Importance
Example for geodata Example for geodata Geodata are all information that can be assigned directly or indirectly to a place on the Earth. This assignment is called");georeferencing"); or ");spatial reference");.
Georeferencing by <br>coordinates Georeferencing by 
coordinates
A ");direct georeferencing"); is made by giving coordinates in a coordinate reference system that consists of a coordinate system and its relation to the Earth body. Examples for Germany are Gauß-Krüger and UTM coordinates. The latter are also used worldwide within the frame of the satellite-based positioning system GPS (Global Positioning System).

Link:
Databank Coordinate Reference Systems:http://www.crs-geo.eu
Assigning statistical );<br> data to municipalities Assigning statistical );
data to municipalities
A ");indirect georeferencing"); is made by assigning objects or factual information to other geo-objects the position of which is known. Area-wide indirect referencing systems are e.g. administrative units or zip code districts.
Topographic map Topographic map Geodata are distinguished to basic geodata and special geodata. Basic geodata are topographic fundamental data. These are made available in Germany as neutral state provisional task by the State survey institutions of the Federal States and by the BKG. All other spatially related information from environment, economy, population etc. is named special geodata.

Link:
Comprehensive treatment of geodata by the Federal Government: http://www.imagi.de
Vector data with objects Vector data with objects Geodata with direct georeferencing may be assigned to three fundamental data types. );

Vector data describe the geometric position of topographic objects by single points or sequences of support points that form lines and areas. By connecting the geometry with factual attributes objects are formed. Geographic Information Systems (GIS) allow the recherche and complex evaluation of this information.
Raster data Raster data Raster data come as a rule from scan processes and describe the geometric position of objects as picture information where the whole area is decomposed into regularly arranged pixels.
Digital Terrain Model Digital Terrain Model Grid data describe a fact by a regularly arranged point grid. Each point bears particular factual information, e.g. the relief height in this point.

An overview

Geodata gain a growing importance in the modern society. Each human activity has somehow or other a spatial relation. The design and change of our environment is based on the governing of geodata as well as the search for a particular route.

Digital geodata allow there the spatial orientation and analytical evaluation of basic and special data on a new technical level. Complex automated and fast evaluations belong to the new possibilities as well as the linking with regional services.



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Basic Geodata - an overview
The official basic geodata are classified into the product ranges
  • Topographic basic geodata
  • Real-property-describing basic geodata and
  • Geodetic basic geodata.


The GeoDatenZentrum processes and sells "Topographic basic geodata". In the following the essential product groups of this data range are given.

Digital Landscape Models (DLM)
example of simple <br>screen graphics <br>for the Basis-DLM example of simple 
screen graphics 
for the Basis-DLM
Digital Landscape Models describe the topographic objects of the landscape (settlements, water bodies, traffic, etc.) and the relief of the Earth surface in the vector format. The objects are assigned to a particular object type and are defined by their spatial position, their geometrical type (point, line, area), describing attributes (e.g. geographical name) and relations to other objects (relations, e.g. underpass). Which object types are contained in a DLM and how the objects are formed is determined in the Object Catalogue.

The following DLM exist or are just being developed (order starting with the highest information density, additional information: scale):

- Digital Basic Landscape Model - Basis-DLM (1:25,000)
- Digital Landscape Model 50 - DLM50 (1:50,000, geplant)
- Digital Landscape Model 250 - DLM250 (1:250,000)
- Digital Landscape Model 1000 - DLM1000 (1:1,000,000)

Digital Terrain Models (DGM)
Graphical representation );<br> of a detail );<br> of the DGM250 Graphical representation );
of a detail );
of the DGM250
Digital Terrain Models are points arranged in regular grids that describe the terrain forms of the Earth surface(grid data). The points are geocoded in position and height.
Digital Terrain Models can also contain additional information (e.g. breaklines, linear relief symbols, single ground level points).

The following DGM exist or are being developed (order starting with highest quality level, additional information: scale and grid spacing):

- Digital Terrain Model 5 - DGM5 (1:5,000, 10-20 m)
- Digital Terrain Model 25 - DGM25 (1:25,000, 20-50 m)
- Digital Terrain Model 50 - DGM50 (1:50,000, 50-100 m)
- Digital Terrain Model 250 - DGM250 (1:250,000, 200 m)
- Digital Terrain Model 1000 - DGM1000 (1:1,000,000, 1 000 m)

Not every Federal State disposes yet area-wide of all models from the range of the high and medium quality levels. The DGM250 and the DGM1000 are made available by the BKG.
Digital Topographic Maps (DTK)
Detail from <br> DTK200-V Detail from 
DTK200-V
Digital Topographic Maps are raster DATA OF THE existing Topographic Maps. THE raster DATA are structured according TO cartographic CONTENTS elements INTO various layers (settlement, traffic, water bodies, vegetation, relief, etc.) AND are available AS SINGLE layers AND AS color combination OF ALL layers (map)
THE DTK-V that were up TO now GENERATED BY scanning THE analog originals AND BY computer-aided UPDATING will IN future be replaced BY DTK that are directly derived FROM a corresponding ATKIS-DLM.
THE FOLLOWING DTK exist:

- Digital Topographic Map 1:25,000 - DTK25-V
- Digital Topographic Map 1:50,000 - DTK50-V
- Digital Topographic Map 1:100,000 - DTK100-V
- Digital Topographic Map 1:200,000 - DTK200-V
- Digital Topographic Map 1:500,000 - DTK500-V
- Digital Topographic Map 1:1 000,000 - DTK1000

Interactive Maps on CD-ROM
Interactive Maps TOP200 Interactive Maps TOP200 Digital Topographic Maps, area maps or special maps of a State or part of a State in various scales that are especially edited with the purpose of screen presentation and that are enriched with additional data (e.g. index of geographic names, administrative borders, Digital Terrain Model). On the CD-ROM there is software for a manifold presentation of the data with partly far-reaching special functionalities (e.g. drawing facilities, GPS connection, perspective terrain views, stereo viewing and others).
For the whole Federal Republic is available the product Top50 of the State surveying institutions and the Top200 of the BKG.

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Last revison:19.01.2018