Route-planning on the spheroid gridded by a DTEM

"Route-planning for vehicles and motion-planning for robots is most effective, and most challeging technically, when it is performed in realtime by on-board computer-processors. The realtime planning allows for responses to changes in the surroundings asthe vehicle or robot proceeds towards a goal from a start. En route planning is accomplished by the repeated execution of sophisticated search procedures on the computer-processors to identify the quickest route to the goal from the current location,which route also avoids obstacles and minimizes the exposure to hazards and threats along the way. The present effort is to develop search-procedures not for a plane surface, but for a curved surface, namely the earth modeled as a spheroid. The earth'sterrain, that is, the actual surface of the earth as it lies above or below the spheroidal model at each pair of numerical values for longitude and latitude, is modeled by a digital terrain elevation matrix (DTEM.) This DTEM imposes a grid on thespheroid consisting of regularly spaced parallels of latitude and regularly spaced meridians of longitude, a geometry different from the rectilinear gridding on the plane surface, which rectilinear gridding is the geometric basis for conventionalsearch-procedures. The grid imposed on the spheroid by the DTEM will be accomodated by the search-procedures to be developed on the present effort. Realtime, on-board route-planners are already in use, as,