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Goldenhuber Christine

Detecting numerical problems in geodetic software


As a consequence of the automation of calculation processes the demands on geodetic software have risen tremendously. Automation, as a rule, puts an end to direct checking by the user. This means that the software needs to be extremely reliable and intelligent.

In particular numerical weaknesses may result in hidden mistakes or cause program crashes. Hidden mistakes produce results that are not entirely wrong and are therefore not found immediately. Program crashes may cause data losses. This paper therefore focuses on the finding of numerical errors. It has been the aim of this paper to work out concrete tests which enable users to check their software with a view to numerical weaknesses. Tools have been worked out and precise instructions for program testing have been included.

The methods applied are derived from that field of software engineering which is concerned with program testing. The program is looked at as a black box into which inputs are fed and from which outputs are expected. Test specifications for each test case contain precise instructions for the performance of each test, the test data proper and finally the correct results. Evaluation of the test results has been based on standard DIN 66 272 "Software product evaluation". An evaluation chart has been worked out to categorize and assess the individual test cases.

To try out the effectiveness of the test cases worked out the author has examined and assessed two software products. The results have shown that the tests are successful in finding numerical weaknesses and in identifying differences in quality between the individual programs.

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