[Proj] +towgs84 approximation error

Noel Zinn (cc) ndzinn at comcast.net
Tue Mar 28 08:40:45 EST 2017

So many options, Jochem!  Old-timer that I am, my field experience in the 
late 1970s and 1980s was occupying triangulation (and traverse) points with 
JMR and Magnavox TRANSIT receivers.  Stochastic noise was generous with both 
technologies.  So, let's do something different.  How about minimal 
stochastics and extreme rotations?  That should exacerbate the deficiencies 
of either an ill-determined 7-parameter derivation or multiple regression 
equations (with 7 coefficients among them, yet to be derived).  Handle the 
vertical as you prefer.  OK?  -Noel

Noel Zinn, Principal, Hydrometronics LLC
+1-832-539-1472 (office), +1-281-221-0051 (cell)
noel.zinn at hydrometronics.com (email)
http://www.hydrometronics.com (website)

-----Original Message----- 
From: Jochem
Sent: Tuesday, March 28, 2017 2:34 AM
To: proj at lists.maptools.org
Subject: Re: [Proj] +towgs84 approximation error

Hi Noel,

Thanks for your friendly response. I am back in the Netherlands now with my
normal duties. Therefore, it took a bit more time to reply.

The country I visited is definitely not a country where Gauss has been
working, considering the large rotations and scale factor.

Regarding the challenge: If you like more stochastic noise in the
observations, we can take the original coordinates of the triangulation. I
am most interested in the effect for the Netherlands (rotation angles up to
2 arc-seconds). Or would you like 40 arc-second rotations better? The
ellipsoidal heights in the old triangulation are close to the levelling
heights, or I could use our precise national geoid to compute ellipsoidal

Regards, Jochem

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