[Proj] cs2cs's +towgs84 usage

[Mikael Rittri]

Clifford Mugnier wrote:
 
> Both sides of the Atlantic have been pretty consistent for over a
century ... 
> that's not arbitrary to me.
 
I don't know anything about photogrammetry or stereoplotters.
But for publishing datum shifts, there are many countries in 
Europe that use the "American" Coordinate Frame Rotation 
(Sweden, Finland, Belgium, Luxembourg, the Netherlands, Hungary,
 Slovenia, ...) 
    It is true that EuroGeographics uses only the "European"
Position Vector Transformation, but so does NATO 
(http://earth-info.nga.mil/GandG/coordsys/datums/helmert.html). 
 
dan Streebe wrote: 

> > The terms "left-handed" and "right-handed" are just as bad. 
> 
> Are they? Those terms are standard in mathematics, where 
> "Position Vector Transformation" and "Coordinate Frame Rotation" 
> are unknown. There is no ambiguity in their meaning or usage.
> 
> (Not that I would advocate using the terminology in this context, 
> since EPSG's terminology is Position Vector Transformation versus 
> Coordinate Frame Rotation. But at least it is not arbitrary like
> "American" versus "European".)

Noel Zinn has already replied to this.  I will just add that 
Clifford Mugnier says that the Coordinate Frame Rotation is 
right-handed, while the British Ordnance Survey says that it 
is the Position Vector Transformation that is right-handed. 
http://www.ordnancesurvey.co.uk/oswebsite/gps/information/coordinatesyst
emsinfo/guidecontents/guide6.html

Ilumas wrote:
> what if the Method is:
>
>     Method [Geocentric translations (geog2D domain)]
>
> and the Sign reversible field value is YES for all 
> three parameters?

The Geocentric Translations can be regarded as a special case
of the 7-parameter transformation, where the rotations and 
the scale difference all are zero. Then there is no problem 
with rotation sign convention. And the EPSG has standardized
on publishing datum shifts in the direction _to_ WGS84. 
So you can just write 

     +towgs84=dx,dy,dz

where the dx, dy and dz are the X-axis translation etc. as 
given by EPSG.

best regards,

--
Mikael Rittri
Carmenta AB
SWEDEN
www.carmenta.com 

________________________________

From: proj-bounces at lists.maptools.org
[mailto:proj-bounces at lists.maptools.org] On Behalf Of strebe
Sent: den 23 april 2010 20:47
To: PROJ.4 and general Projections Discussions
Subject: Re: [Proj] cs2cs's +towgs84 usage

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