[Proj] Projection advice

Roger Oberholtzer roger at opq.se
Thu Dec 8 10:10:39 EST 2011

On Thu, 2011-12-08 at 06:41 -0600, Noel Zinn (cc) wrote:
> Roger,
> Presumably you want a conformal projection so that the scale distortion is 
> uniform in all directions.  


> Does the INS fiddling in Northings/Easting 
> account for scale distortion (point scale factor) at all, or does it presume 
> there is no scale distortion?  If the latter, then the larger the area your 
> generic projection covers, the greater the scale distortion your INS 
> fiddling will ignore.  That may not be a good change from your current, 
> local-projection procedure.

The INS is comprised of 3D gyroscopes, multi-axis accelerometers, a
wheel pulse transducer, and in some cases inclinometers. From these is
obtained very accurate relative movement information. Drift is minimal
over the distances it is expected to be used. These devices are scaled
and offset against a well-defined surface in the general area (within
the same country...) as they are used. Gravitational and surface curve
effects are minimal over the short distances they are used. At least
that is our working model.

Yours sincerely,

Roger Oberholtzer

OPQ Systems / Ramböll RST

Office: Int +46 10-615 60 20
Mobile: Int +46 70-815 1696
roger.oberholtzer at ramboll.se

Ramböll Sverige AB
Krukmakargatan 21
P.O. Box 17009
SE-104 62 Stockholm, Sweden

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