[Proj] Hristow

Oscar van Vlijmen ovv at hetnet.nl
Tue Oct 25 08:22:32 EDT 2005

> From: "Gerald I. Evenden"
> Date: Mon, 24 Oct 2005 13:11:56

> On Monday 24 October 2005 11:28 am, Clifford J Mugnier wrote:
>> The Roussilhe Stereographic Projection was published in the early 1900s by
>> the Hydrographer of the French Navy, Roussilhe.  Although his formulae,
>> adopted by several European Powers, are computationally unique;
>> (Note there is ALSO the Hristow Stereographic Projection as used in Romania
>> as the "Stereo 70.")  Roussilhe (Russell), was French; Hristow was
>> Bulgarian and he published in German.
> Hmm.  Now to figure out where to get a copy of the math for Hristow.

Mr. Mugnier gives a test point in "Grids & Datums - Romania"
BTW, I believe the central latitude is at 46d, not 45d.
See also EPSG ProjCRS 31700.

With (my version of) sterea (double stereographic projection) and the
following parameters I got:

lat=44d 30m 30s; lon=26d 3m 3s;
lat0=46; lon0=25; x0=5e5; y0=5e5; m0=0.999750;
Krasowski ellipsoid;
-> easting = 583553.82638, northing = 334794.54321
(another instance of y=easting)
The article gives: northing x = 334794.541, easting y = 583553.824
So, less than 2.5 mm difference.

I am looking forward to the actual Hristow series, but in the mean time one
could use sterea.

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