Class RangeCoordinates

java.lang.Object
edu.nps.moves.spatial.RangeCoordinates

public class RangeCoordinates extends Object

Represents a local, flat range area with Euclidean coordinates, which is convenient for somewhat small simulated areas. This class assumes a local, flat, coordinate system with an origin at (lat, lon, altitude) and positive X pointing local east, positive Y pointing local north, and positive Z pointing up. Specified in WGS_84 geodesic coordinate system. Altitude is distance above the ellipsoid.

The coordinate system has its origin at the given (lat, lon) and creates a plane tangent and normal to the ellipsoid at that point.

There are several major reference frames that may be useful in various contexts:

Geocentric: Origin at the center of the earth. Positive X out at the intersection of the equator and prime meridian, Y out at 90 degrees east lon, and Z up through the north pole. This is the coordinate system used by DIS world coordinates.

Geodetic: The coordinate system uses lat/lon/altitude. This is handy for positioning an object on the earth (or close to it) but not so handy for describing things like velocity.

Local Tangent Surface Euclidean (LTSE): Pick a lat/lon/altitude, and then at that point you can define a single plane normal and tangent to the globe. Positive X points local east, positive Y points local north, and positive Z points local up. This is handy for describing the position of an object in, for example, a range of somewhat small dimensions, perhaps 20KM X 20KM, where we don't want to get sucked into the whole curved earth scene and just want to be simple.

Body Centric/Lococentric/Platform-centric: The origin is at the volumetric center of an entity (in DIS); Positive x points out the long axis, positive Y points to the right, and positive Z points down. This is widely used to describe (roll, pitch, yaw) in aircraft. Note that you need a transform from (for example) the LTSE to body coordinates to define the position of the body axis origin and orientation WRT the LTSE origin. Note that the direction of the Z axis is the opposite of that used by LTSE. The axes are often named (u,v,w) in this frame of reference.

We can also convert between these coordinate systems using standard libraries in the SRM.

See User’s Manual for SRM Orientation, Velocity, and Acceleration Transformations Version 2.0, 18 Nov 2009, available with the sedris Java SDK download.
Author:
DMcG