# RE: MI coordsys transformation

```Walter,

Have you considered using the AFFINE clause that could register any DXF in
any "orthogonallly projected" or non-earth coordsys? The only delicate point
is the calculation of the 6 parameters, difficulty residing essentially in
the understanding of the direction of the change.

I have detailled that question in chap 8 Registering a DXF map in "My Bag
o'Tricks". I must have some Excel spreadsheet that would help in the
computation of those parameters; if you think it could be of help, ask and
I'll see what I can do.

Jacques Paris
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gis activity (MapInfo mainly)
http://www.total.net/~rparis/gisproducts.htm
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> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED]]On Behalf Of [EMAIL PROTECTED]
> Sent: July 14, 1999 3:15 AM
> To: [EMAIL PROTECTED]
> Subject: MI coordsys transformation
>
>
>
> Hello mappers,
> Are there some experts on coordsys transformations out there? In
> the field Arheologists often work with a local coordsystem
> (nonearth meters). During the gis analysis we want to place all
> the information in an national non-earth(meters)coordsys.
> Until now I used Rotator from the ftp-site. This works very
> well, but I need to determine the angle of rotation and the
> X, Y translation parameters. I think, it would be better to
> digitize the excavation drawings directly in the
> national nonearth coordsys by using control points from which
> the national coordsys coordinates are used
> (there are always points in the field from which both coordsys
> coordinates are known).
>
> I would like to build a program (mbx) that asks the user- from
> two points(is this enough?), both local and
> national coordinates. The program then calculates the rotation
> angle and the translation parameters. Then the user can give
> a number of local coordinates and the program can calculate from
> every local coordinates the national coordinates.
> Is this possible with some simple goniometry and pythagoras?
> Is there some information on this subject (books, internet)?
>
> Walter
>
>
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