Although the packages have nearly identical purposes, their philosophies, approaches, emphasis, capabilities,and presentations of the results are very different. Table 1 gives a summary of intercomparisons among functions, constraints considered, limitations and hardware enviroment. Lots of subtle differences remain hidden however which make the packages more or less user friendly. Some examples: The coordinate system used for station coordinates are different and definitions are sometimes missing. The system of orbital elements is similar in the case of FAKESAT, SVPIS, SPAS, but different in RASTRON. Changing parameter values and configuration setup is often cumbersome. Not even the vocabulary is common among the packages. There are often different names for the same function or parameter.
The differences are understandable if we consider the very different roots and environment of the software developments. Newertheless, the many differences made intercomparisons a difficult task and can be quite confusing for the international user community.
Agreement in the results do not exclude errors, only increase confidence that the results are correct. Comparisons to fully independent external numeric examples are also necessary to validation. This task is the responsibility of each developer.