The Topographic Landscape Model TLM

The Topographic Landscape Model TLM replaces the map-based models VECTOR25, SwissNames and GG25 from swisstopo. The TLM is an immense 3D geodatabase and covers the whole of Switzerland as a comprehensive basic landscape model. The natural and artificial features in the landscape such as roads or watercourses are displayed as three-dimensional vectors and grouped into nine categories:

The content of the TLM and the landscape feature definitions were developed in cooperation with various professional institutions from both the federal government and the cantons. Geometries and a wide range of attributes are provided for all landscape features. The height reference is captured by using a 3D display or provided by the Digital Terrain Model (DTM), which also forms part of the TLM. The geometries are not cartographically generalised and provide an accuracy of between 0.2 and 1.5 m for well-defined landscape features such as buildings or roads in all three dimensions. Landscape features such as forests which are not so clearly defined have an accuracy of between 1 and 3 m.

The TLM is a production model which is used as a basis at swisstopo to create the national maps to a scale of 1: 25'000, 1: 50'000 and 1: 100'000, as well as additional 3D data sets.

Natural and artificial landscape features

Compared with the existing geodata (VECTOR25, SwissNames, etc.) the TLM not only offers higher geometric accuracy, but is also more extensive and up-to-date.

The existing data was migrated into the TLM as a basis. The data is then updated based on an update cycle of 6 years and improvements and additions are made to the geometries and attributes. While the update process in the update blocks 2008, 2009 and 2010 is in progress, the systematic improvement of the geodata to achieve TLM quality will not started before block 2011.

Parallel to the six-year update process, an annual update is carried out through the integration of data from so-called reference partners for selected topics. Initially, this annual update is implemented mainly for the administrative boundaries, buildings and road links. The official cadastral survey plays an important role as a reference partner in this process. The nomenclature for updating names are also integrated from the official cadastral survey.

Terrain

Existing data is used as a basis:

• For areas less than 2000 m above sea level: data from the laser point survey flights 2000 - 2008
• For areas more than 2000 m above sea level: DHM25

The laser point data is updated in accordance with the TLM update cycle of 6 years. During this process, the dots are deleted and new points, breaklines and areas are set. For example, incorrect points in areas around bridges are removed and an enclosing breakline (enclosure) is implemented for lakes.

In order to meet the requirements of the TLM with regard to accuracy in areas lying more than 2000 m above sea level, the DHM25 will be replaced in 2010-2012 with more accurate data gained via autocorrelation of aerial photographs. This newly generated data will also be updated in the TLM update cycle.

Various 3D data sets extracted from the TLM are available since autumn 2010. They comprise the entire territory in reduced form - measured according to the final requirements of the TLM. To be more precise, the number of landscape features on offer is reduced compared with the TLM landscape feature catalogue and the geometric accuracy in the areas where the systematic improvement has not yet been made corresponds to that of data set VECTOR25. This is an initial version (1.0) of the products extracted from the TLM.

The systematic improvement of the data will mean that a Version 2.0 of the various products can be made available alongside Version 1.0. Version 2.0 will be made available sector by sector in accordance with the update blocks. It will contain significantly more landscape features, offer a higher geometric accuracy for all data and will therefore fulfil the requirements with regard to TLM quality.