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The fixed 60 degrees offset at EHAL turned out to be the lattitude offset (actually 53.45 degrees): The moon seems to be dragging the tide with an almost perfect 45 degrees 'bow-wave' along the equator.

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Erik Hofman 2020-10-27 08:31:54 +01:00
parent 7510f7d487
commit 46435edf19
2 changed files with 13 additions and 2 deletions
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14
src/Time/tide.cxx
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@ -37,6 +37,8 @@ void FGTide::bind()
SGPropertyNode *props = globals->get_props();
viewLon = props->getNode("sim/current-view/viewer-lon-deg", true);
viewLat = props->getNode("sim/current-view/viewer-lat-deg", true);
_tideAnimation = props->getNode("/environment/sea/surface/delta-T-tide", true);
_tideLevelNorm = props->getNode("/sim/time/tide-level-norm", true);
@ -46,6 +48,8 @@ void FGTide::bind()
void FGTide::unbind()
{
viewLon.reset();
viewLat.reset();
_tideLevelNorm.reset();
_tideAnimation.reset();
}
@ -56,8 +60,14 @@ void FGTide::update(double dt)
FGLight *l = static_cast<FGLight*>(globals->get_subsystem("lighting"));
// Don't know where the 60 degrees offset comes from but it matches
// the tides perfectly (at EHAL). Something to figure out.
double viewer_lon = (viewLon->getDoubleValue() + 60.0)*SGD_PI/180.0;
// the tides perfectly at EHAL. Something to figure out.
// Eureka: It was the latitude (53.45 degrees north).
// It turns out that the moon is draging the tide with an almost
// perfect 45 degrees 'bow-wave' along the equator. Tests at SMBQ
// (0 degrees latitude) confirmed this finding.
double viewer_lon = (viewLon->getDoubleValue()
+ fabs( viewLat->getDoubleValue() )
) * SGD_DEGREES_TO_RADIANS;
double moon_lon = l->get_moon_lon() - viewer_lon;
if (fabs(_prev_moon_lon - moon_lon) > (SGD_PI/360.0))
{

1
src/Time/tide.hxx
View file

@ -54,6 +54,7 @@ private:
double _tide_level = 0;
SGPropertyNode_ptr viewLon;
SGPropertyNode_ptr viewLat;
SGPropertyNode_ptr _tideLevelNorm;
SGPropertyNode_ptr _tideAnimation;
};