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Merge /u/dirteat/flightgear/ branch next into next

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https://sourceforge.net/p/flightgear/fgdata/merge-requests/172/
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James Turner 2020-03-11 09:44:21 +00:00
commit 556c19e1ee
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@ -45,6 +45,9 @@
# useful for map distance
# .direct_distance_to(<coord>) ... distance in m direct, considers altitude,
# but cuts through Earth surface
# .greatcircle_distance_to(<coord>, <coord>) ... returns distance to a great circle (in m along Earth curvature)
# defined by two points
# .horizon() ... returns distance to the horizon in m along Earth curvature, ignoring altitudes
#
#
# MANIPULATION METHODS:
@ -221,6 +224,65 @@ var Coord = {
var dz = dest._z - me._z;
return math.sqrt(dx * dx + dy * dy + dz * dz);
},
# arc distance on an earth sphere to the great circle passing by A and B; doesn't consider altitude
greatcircle_distance_to: func(destA, destB) {
me._pupdate();
destA._pupdate();
destB._pupdate();
# AB is not a circle but a point
if (destA._lat == destB._lat and destA._lon == destB._lon) {
return me.distance_to(destA);
}
var ca1 = math.cos(destA._lon);
var cd1 = math.cos(destA._lat);
var sa1 = math.sin(destA._lon);
var sd1 = math.sin(destA._lat);
var ca2 = math.cos(destB._lon);
var cd2 = math.cos(destB._lat);
var sa2 = math.sin(destB._lon);
var sd2 = math.sin(destB._lat);
var sa12 = math.sin(destA._lon - destB._lon);
var ca3 = math.cos(me._lon);
var cd3 = math.cos(me._lat);
var sa3 = math.sin(me._lon);
var sd3 = math.sin(me._lat);
# this is sin(greatcircle_dist) * sin(arcAB)
var sDsAB = cd3 * sa3 * (ca2 * cd2 * sd1 - ca1 * cd1 * sd2 )
+ ca3 * cd3 * ( cd1 * sa1 * sd2 - cd2 * sa2 * sd1 )
- cd1 * cd2 * sd3 * sa12;
# direct calculation of sin(arcAB) to not call sin(arcsin(distance_to))
var a = math.sin((destA._lat - destB._lat) * 0.5);
var o = math.sin((destA._lon - destB._lon) * 0.5);
var hs12 = a * a + cd1 * cd2 * o * o;
var hc12 = 1.0 - hs12;
# AB is undertermined; a great circle should be defined with non-colinear vectors
if (hs12*hc12 == 0.0) {
die("Great circles are defined with non-colinear vectors");
}
return ERAD * math.abs( math.asin( 0.5 * sDsAB / math.sqrt( hs12 * hc12 ) ) );
},
# arc distance on an earth sphere to the horizon
horizon: func() {
me._pupdate();
if (me._alt < 0.0) {
return 0.0;
}
else {
return ERAD*math.acos(ERAD/(ERAD+me._alt));
}
},
is_defined: func {
return !(me._cdirty and me._pdirty);
},