Re: Gama usage question

Hi Greg,

I think you are right it isn't the right tool. Everything is 
constrained in my data, I just want to 1) determine and 2) apply a 7 
DOF operation (3 translate, 3 rotate, 1 scale). I was hoping Gama 
might help with that.

Thanks,

   -k.

On Wed, 5 Dec 2012, Greg Troxel wrote:

>
>  I have a large point-cloud. I would like to convert coordinate
>  systems, a 7-DOF rotate, translate, and scale.
>
> My quick reaction is that gama isn't the right tool, since it's about
> estimating coordinates given observations.  If you already have an
> internally-consistent point cloud, then you aren't estimating
> coordinates.
>
> I think your problem has two sub-parts:
>
>  estimating the rotation/translation/scale
>
>  applying it
>
> Applying it is similar to datum transformation, except that datum
> transformations are typically small angles.
>
> It may be that part of the gama code is helpful.
>
> Given only two control points, I would think you could
>
>  transform the control points real coordintes to ECEF XYZ (via proj4)
>
>  compute translation, scale
>
>  compute/choose an orientation, because you're down a control point
>
> pretty easily, with the last two steps being done with a calculator
> even.
>
> Then, you could end up with rotate and translate matrices, and apply
> them with octave.
>
>
> If you had more control points, you'd be in a least-squares situation
> (and better off data wise with a harder processing problem, really :-).
>
> It may be that having framed the problem of multiple control points with
> coordinates in two different systems, you can write code to use the
> solver in gama to solve that different problem.  But I'd expect the bulk
> of gama to be about computing the partial derivatives of the types of
> observations used in surveying.
>