# Thread: formula to convert coordinates from one grid to another?

1. ## formula to convert coordinates from one grid to another?

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Hi

I have coordinates on one grid system.I have a drawing with this coordinate system overlaid on another system. My client wants a formula so that he can take a coord on the first grid and convert it to a coord on the second. Does anyone know the formula for doing this?

I'm sure it can be done because i think i remember someone giving me it years ago.

Fingers crossed!
Thanks

2. If you have two drawings which happily register on top of each other, why go for the mathematicals when you can do it graphically?

Set up a UCS at the 0,0 point of the second grid and aligned to that grid. Then you can ID any point and get its coordinates.

3. You must know the relation between the two coordinate systems. In 2D you can go from one to the other by a rotation and a translation. If you work in 3D, a translation and 3 rotations will transform the coords.
Knowing the translation and the rotation(s) between the two systems, you can apply the transformations to all your points.

4. I know how to do it in AutoCAD.

The problem is that my client doesn't and will not be using AutoCAD. The work I'm doing will be exported to Adobe CS3 and drafted for publication.

He wants a way of converting the coords when I'm not working for him.

5. You can probably get an Excel spreadsheet to do just that. Even I wrote one some eons ago, but it is finding the formula that is tricky.

I just put in a Google search in the UK for "coordinate geometry transformation 2d" , and the first one on the list was http://www.engineeringsurveyor.com/utilities/index.htm

I am sure you can go from there.

6. Here's a US Army Corps of Engineers program for just that:

http://crunch.tec.army.mil/software/.../corpscon.html

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Originally Posted by eldon
You can probably get an Excel spreadsheet to do just that. Even I wrote one some eons ago, but it is finding the formula that is tricky.

I just put in a Google search in the UK for "coordinate geometry transformation 2d" , and the first one on the list was http://www.engineeringsurveyor.com/utilities/index.htm

I am sure you can go from there.
Thank again Eldon, i'd done a google search but obviously used the wrong words.

I think that first link should do what i want.

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