New Nasal method get_cart_ground_intersection
Returns where the given position in the specified direction will intersect with the ground. Returns whether or not a certain position and direction pair intersect with the ground, and if so the intersection point.
Useful for radars, terrain avoidance (GPWS), etc.
Input parameters:
1. vec3d(x,y,z) position
2. vec3d(x,y,z) direction
Returns nil or geod hash (lat:rad,lon:rad,elevation:Meters) intersection
Example Usage:
var end = geo.Coord.new(start);
end.apply_course_distance(heading, speed_horz_fps*FT2M);
end.set_alt(end.alt() - speed_down_fps*FT2M);
var dir_x = end.x() - start.x();
var dir_y = end.y() - start.y();
var dir_z = end.z() - start.z();
var xyz = { "x":start.x(), "y" : start.y(), "z" : start.z() };
var dir = { "x":dir_x, "y" : dir_y, "z" : dir_z };
var geod = get_cart_ground_intersection(xyz, dir);
if (geod != nil) {
end.set_latlon(geod.lat, geod.lon, geod.elevation);
var dist = start.direct_distance_to(end)*M2FT;
var time = dist / speed_fps;
setprop("/sim/model/radar/time-until-impact", time);
}
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Nasal method aircraftToCart : This allows easily computing offsets in aircraft-relative coordinates, and converting to global cartesian (ECEF) reference frame.
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