State-of-the-art of automated generalisation in commercial software

State-of-the-art of automated generalisation in commercial software

Stoter, J.E.
Baella, B.
Blok, C.
Burghardt, D.
Duchêne, C.
Pla, M.
Regnauld, N.
Touya, G.

OTB Research Institute

OTB onderzoek

2010-03-01

This report presents the EuroSDR research project that studied the state-of-the-art of automated generalisation in commercial software in a collaboration between National Mapping Agencies (NMAs), research institutes and vendors. The aims of the study were to learn more about generic and specific map requirements of NMAs, to show possibilities and limitations of commercial generalisation software, and to identify areas for further developments based on latest research advances. The project consisted of three main steps: requirements analysis, testing, and evaluation. The requirement analysis (carried out between Oct 2006 till June 2007) resulted in four representative test cases, formalised and harmonised NMA map specifications for automated generalisation as well as an analysis of the defined specifications that shows the similarities and differences between map specifications of different NMAs. Between June 2007 and Spring 2008 tests were performed by project team members (from NMAs and research institutes) on out-of-the-box versions of four generalisation systems: ArcGIS (ESRI), Change/Push/Typify (University of Hanover), Radius Clarity (1Spatial) and axpand (Axes Systems). At the same time the vendors (except Axes systems) carried out tests with the same test cases with improved and/or customised versions of their systems. The tests resulted in 35 outputs consisting of 700 thematic layers, where it should be noted that the effort for one test was approximately 1 week. The evaluation, carried out between summer 2008 and spring 2009, consisted of an evaluation of meta aspects (based on information recorded by the testers) and of an evaluation of the generalised datasets themselves. The latter evaluation consisted of three parts that completed each other: a) automated constraint-based evaluation, b) evaluation which visually compared different outputs for one test case and c) a qualitative evaluation by cartographic experts. From the project results it can be concluded that all systems offer potentials for automated generalisation. However the results highlighted a few issues that identify areas for further development in both research and commercial systems. Although the results show that for many problems solutions do exist (e.g. building simplification), the algorithms are difficult to parameterise and a direct match between parameters and specifications was often missing. In addition none of the four test cases were fully solved by the out-of-the-box systems. While some problems are close to being solved (generalisation of individual buildings and roads), a few problems are far from being solved. Firstly it is impossible with the tested systems to apply different algorithms and/or parameter values in different contexts. This is either not supported or a measure to detect the appropriate contexts is missing. Another remaining generalisation software problem is operations that concern more than one object (e.g. network typification). Also, the generalisation of the topographic context in an integrated manner with the terrain is not appropriately covered in the tested systems. It should be noted that some of the missing functionalities were fixed in the vendors’ parallel tests (e.g. buildings elimination and displacement algorithms in ArcGIS and Radius Clarity). Although these results may seem disappointing, some final thoughts may help to put the results in the right context. Firstly the project had very high ambitions (i.e. many specifications were defined; the selection of test cases focused on known and complex problems; the ultimate aim of the generalisation process was high quality paper maps). Secondly, the project is well received by vendors to push internal developments. In addition it is not a surprise that out-of-the box versions are not capable of fulfilling NMA requirements, which is also shown by the fact that customised systems are used more satisfactory in practice. Consequently customisation of the systems should be further developed and should be one of the focuses in a future project.

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(c) 2010 The Author(s)