Inaccuracies when mixing coordinate reference frameworks in a system of systems simulation

The modelling of military systems of systems invariably involves the incorporation of existing, often shared, models into larger and more complex simulations. The sharing of models between simulations has long been the goal of the simulation community and although the resulting simulations expand the application domain of the models it comes at a cost. In this paper the authors highlight one of the issues faced, namely the use of different coordinate frameworks on performance and quantifies the errors that could be introduced into the simulation. It starts by providing an overview of the most commonly used coordinate frameworks and then elaborates on some of the experiences gained through its application in the Virtual Ground Based Air Defence System (GBADS) simulator. The focus is on the mixing of flat earth convention and spherical earth convention. The authors conclude with further motivation why a common earth reference model should be used for all simulation entities and, more importantly, why it should be a "real world" earth reference model.