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Quality Evaluation Services on the
Internet
Anders Ostmanl
Abstract. - Current methods for quality evaluation are often suited for
data producers and not for data users. Depending on type of data and
production methods used, data producers may utilize different quality
evaluation techniques such as product testing, prototype testing, error
propagation studies or expert evaluations. An ordinary data user is
however usually producing results without having access to proper
quality evaluation procedures.
A research program have been established at the University of Lulei,
Sweden, aiming at developing quality evaluation procedures for casual
G I s users. The approach taken here is to design and implement
distributed and harmonized quality services in various environments.
These services are then used as building blocks in the design of quality
evaluation procedures for casual users. In this paper, two initial studies
within this program are presented.
Error propagation studies and Monte Carlo simulators are important tools
within quality systems for spatial data. Due to the lack of proper quality
specifications of existing data sets, ordinary users are seldom using
proper quality evaluation procedures. A Monte Carlo simulator for
elevation data has therefore been designed and made available on the
internet. The communication with clients is currently based on email and
the transfer ascii files.
The MC simulator is based on the result of a large international DTM test
conducted by the ISPRS. It is primarly aimed for photogrammetrically
sampled digital elevation models. The client sends an email to the server,
where keywords such as flying height, point density, size of grid, number
of simulations and email return adress are specified. The server then
generates and returns sets of error grids to the specified email adress. The
values in the error grids are spatially correlated according to the results of
the ISPRS DTM test and specified parameters.
Another quality service, which currently is being designed, is test
procedures for quality evaluation of commercial DTM software. Test
data from the ISPRS DTM test is here made public together with quality
evaluation procedures of interpolated terrain surfaces.
Further information concerning this research program and more detailed
information concerning the current quality services is available at the
WWW-site http://www.luth.se/depts/sb/fo_git/.
Professor, Geographic Itlformation Technology, Dept of Environmental Planning and Design, University of Luled,
S-971 87 Luled, SWEDEN. Email: Anders.Ostman@sb.luth.se
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