You're right. I was right thinking about it yesterday while committing the
changes.
*f *is misleading, and it should be substituded by *rf* in my formula.
Thanks for having reported your measurements. They helped a lot to figure
out the bug ;)
giovanni
2012/4/6 blavet
> **
> *Good evening*
>
>
I will read your post with more attention tomorrow.
Anyway, the code is correct now, because my patch was included this morning
:)
giovanni
2012/4/6 blavet
> **
> *Good evening*
>
> Of course thank you again i fully agree with what you found which is
> mathematically correct ,
> it was not eas
Good evening
Of course thank you again i fully agree with what you found which is
mathematically correct ,
it was not easy to find, and is essential for debugging the
calculation of ellipsoîdal distances
I just had a quick look at the code found at
http://trac.osgeo.org/qgis/browser/trunk/qg
Thank you very much for this very fast and efficient diagnosis
Best regards
Didier Blavet
Le 06/04/2012 12:01, G. Allegri a écrit :
Probably I've found the bug.
In Qgis the semi-minor axis of the ellipsoid is calculated with:
b = a - (f/a)
where
b = semi-minor axis
a =
Not at all.
The change has already been committed to the development version.
giovanni
2012/4/6 blavet
> **
> Thank you very much for this very fast and efficient diagnosis
>
> Best regards
>
> Didier Blavet
>
> Le 06/04/2012 12:01, G. Allegri a écrit :
>
> Probably I've found the bug.
> In Qgi
And ticket: http://hub.qgis.org/issues/5329
2012/4/6 G. Allegri
> Pull request done: https://github.com/qgis/Quantum-GIS/pull/115
>
> giovanni
>
>
> 2012/4/6 Paolo Cavallini
>
>> Il 06/04/2012 12:01, G. Allegri ha scritto:
>> > Probably I've found the bug.
>> > In Qgis the semi-minor axis of
Pull request done: https://github.com/qgis/Quantum-GIS/pull/115
giovanni
2012/4/6 Paolo Cavallini
> Il 06/04/2012 12:01, G. Allegri ha scritto:
> > Probably I've found the bug.
> > In Qgis the semi-minor axis of the ellipsoid is calculated with:
> >
> > b = a - (f/a)
> >
> > where
> > b = semi
Il 06/04/2012 12:01, G. Allegri ha scritto:
> Probably I've found the bug.
> In Qgis the semi-minor axis of the ellipsoid is calculated with:
>
> b = a - (f/a)
>
> where
> b = semi-minor axis
> a = semi-majot axis
> f = inverse flattening
>
> while it should be:
>
> b = a - (a/f)
>
>
> In Qg
Probably I've found the bug.
In Qgis the semi-minor axis of the ellipsoid is calculated with:
b = a - (f/a)
where
b = semi-minor axis
a = semi-majot axis
f = inverse flattening
while it should be:
b = a - (a/f)
In Qgis the WGS84 semi-minor axis is 6378136,xxx
while it should be 6356752.xxx
g
AFAICS, the Qgis formula [1] to calculate distances on ellipssoid is
Vincenty's.
I've reproduced it for the first set of points and I can confirm tha QGis
gives 540.9973919726176 m
The online Vincenty calculator [2] gives 540.045 m
I suppose it's a rounding issue.
I will investigate it more...
g
Dear QGis Developpers and Users
First of all many thanks to the Developpers of Qgis for this wonderful
and user friendly Sofwaret. I'm sure that Qgis will become more and
more a "standard" in the next few years
So, just a small point (and I hope to be wrong with this, but if it
is the cas
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