[glideplan_swproj] Re: [glideplan_swproj] Re: [glideplan_swproj] Re: Line drawing

  • From: Tomáš Zámečník <pulcik@xxxxxxxx>
  • To: glideplan_swproj@xxxxxxxxxxxxx
  • Date: Wed, 25 Apr 2012 11:05:08 +0200 (CEST)

Note: FAI sphere is r=6371.0 km

> ------------ Původní zpráva ------------
> Od: Tomáš Zámečník <pulcik@xxxxxxxx>
> Předmět: [glideplan_swproj] Re: [glideplan_swproj] Re: Line drawing
> Datum: 25.4.2012 11:04:22
> ----------------------------------------
> I made some measurements. (attached file)
> There are three tasks with distances measured by updraft, cpska.cz, mapy.cz
> (manual measurement) and FAI Calculator.
> Distances measured by updraft are quite similar to WGS84 (by FAI Calculator).
> There is visible difference
> between FAI sphere and WGS84 (see the results).
> I think, we need following functions in the utils library, computing EXACT
> values:
>
> qreal distance(location1,location2,model)
> qreal course(location1,location2,model)
> // model could be either FAI Sphere or WGS84 (enumerator)
>
> Everywhere in application we should use these functions with model selected by
> user in settings (default WGS84).
>
> Kuba, you can inspire from the javascript FAI Calculator (there is code :) 
> which
> I send as an attachment.
> This program is published at:
> http://www.fai.org/how-to-set-a-record/121-cia/34839-world-distance-calculator
>
> Tom
>
> > ------------ Původní zpráva ------------
> > Od: Kuba Marek <blue.cube@xxxxxxxxx>
> > Předmět: [glideplan_swproj] Re: Line drawing
> > Datum: 24.4.2012 19:36:16
> > ----------------------------------------
> > Look here:
> >
> https://secure.wikimedia.org/wikipedia/en/wiki/Great_circle_distance#Radius_for_spherical_Earth
> > It should be within 1% (?) for the quadratic mean radius that Ales is
> > using. There seems to be another way of calculating it, that works on
> > ellipsoidal earth
> > ( https://secure.wikimedia.org/wikipedia/en/wiki/Vincenty%27s_formulae
> > ), but looks a bit too complicated to me.
> >
> > Harder question now:
> > The great circle distance should be available to all parts of updraft.
> > Where to put it? Utils::Location?
> >
> > K
> >
> > > Hi
> > >
> > > yes it's an approximation that should be sufficient in most of the
> > > cases (imho).
> > >
> > > A.
> > >
> > > 2012/4/24 Tomáš Zámečník <pulcik@xxxxxxxx>
> > >
> > > > This is not distance on ellipsoid WGS84, but on some sphere with r =
> > > > EARTH_RADIUS_IN_METERS.
> > > > T.
> > > >
> > > > > ------------ Původní zpráva ------------
> > > > > Od: Ales Zita <ala.zita@xxxxxxxxx>
> > > > > Předmět: [glideplan_swproj] Re: Line drawing
> > > > > Datum: 24.4.2012 09:56:34
> > > > > ----------------------------------------
> > > > > Hi
> > > > >
> > > > > I use the following distance calculation in airspaces:
> > > > > have a look at
> > > > >
> > > >
> >
> https://github.com/updraft/updraft/blob/master/Updraft/src/plugins/airspaces/oaengine.cpp
> > > > > row 509 :
> > > > > double oaEngine::DistanceInMeters()
> > > > >
> > > > > A.
> > > > >
> > > > >
> > > > > 2012/4/24 Tomáš Zámečník <pulcik@xxxxxxxx>
> > > > >
> > > > > > I don't know how to compute distance on WGS84, maybe there are
> > > > > > some routines in osg/osgEarth.
> > > > > > Have you any idea?
> > > > > > Maybe it would be sufficient to subdivide the line with
> > > > > > osgEarth::Symbology::MeshSubdivider to some level (subdivision
> > > > > > step is defined with radians) and somehow take the data from it.
> > > > > >
> > > > > > T.
> > > > > >
> > > > > > > ------------ Původní zpráva ------------
> > > > > > > Od: Kuba Marek <blue.cube@xxxxxxxxx>
> > > > > > > Předmět: [glideplan_swproj] Re: Line drawing
> > > > > > > Datum: 24.4.2012 00:36:21
> > > > > > > ----------------------------------------
> > > > > > > Is there any realistic chance someone is going to use tasks
> > > > > > > this
> > > > large?
> > > > > > > Because if there is, then I need to fix calculations of task
> > > > > > > distance (now it uses euclidean distance in XYZ, it would
> > > > > > > probably be better
> > > > to
> > > > > > > use great circle distance)
> > > > > > >
> > > > > > > K
> > > > > > >
> > > > > > > > I found an easy way how to draw lines on the earth surface.
> > > > > > > > It can be done with osgEarth::Symbology::MeshSubdivider,
> > > > > > > > which subdivides (any?) geometry according to ellipsoid
> > > > > > > > surface. It's
> > > > very
> > > > > > > > easy to use - just call one method on your geometry and
> > > > > > > > specify wheter you want to interpolate according to great
> > > > > > > > circle or not.
> > > > ...I
> > > > > > > > send screenshot (in attachment) of declaration of 25000km
> > > > > > > > FAI triangle :-)
> > > > > > > >
> > > > > > > > T.
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > >
> > > > > > To visit archive or unsubscribe, follow:
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> > > > > >
> > > > >
> > > > >
> > > > >
> > > >
> > > > To visit archive or unsubscribe, follow:
> > > > http://www.freelists.org/list/glideplan_swproj
> > > >
> >
> >
> >
>
>

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  • » [glideplan_swproj] Re: [glideplan_swproj] Re: [glideplan_swproj] Re: Line drawing - Tomáš Zámečník