The X3D geospatial component: X3DOM implementation of GeoOrigin, GeoLocation, GeoViewpoint, and GeoPositionInterpolator nodes

We present new implementations of important X3D nodes which enable a large class of geospatial applications in standard web browsers. We have chosen the freely available X3DOM code base as an implementation framework since it provides a very functional set of X3D nodes along with a broad selection of support functionality. In our implementations of the GeoOrigin, GeoLocation, GeoViewpoint and GeoPositionInterpolator nodes, we fully conform to the ISO specification and use well known example scenes as references for correctness. While GeoOrigin is deprecated in version 3.3 of the specification, we demonstrate that limited precision in the WebGL rendering pipeline still makes its use desirable at least until alternative solutions are formalized and coded. GeoLocation and GeoViewpoint nodes require specific alignments of coordinate systems which we document in detail. In addition, GeoViewpoint has the property to control navigation speed which conceptually conflicts with user speed control. We resolve this conflict by using relative speed and also make this control optional. Somewhat terse language in the GeoPositionInterpolator specification required clarification of its existing usage and inspired an option for coordinate interpolation along great circles which is often the expected interpolation path in global scenes. Finally, all functionality was integrated into current, stable releases of the X3DOM distribution available from www.x3dom.org.