I THINK I know what you are trying to accomplish, but I don't know much about surveying. What I do know is trig, and I think it can help

What I think you hope to do is map one coordinate system (your data coordinates) to the state plan coordinate system. Fortunately, this isn't all that difficult to do. It will take a small little bit of calculation on your part, along with a formula you can apply to the excel sheet. The part YOU have to calculate is the angle between the data coordinate system, and the state coordinate system.

Wikipedia actually explains this fairly well. Read this first to get an idea on at least the background of what I'm going to do.

We're going to make some slight modifications to that, as that doesn't account for the fact that your state grid size is not the same as the data grid size (i.e. 1 distance unit on the data block does not represent 1 distance unit on the state block).

I'm not sure of your comfort level with trig. I'm going to kind of toss this out here without a great deal of explanation. If anything is confusing at all, I can explain in detail, particularly if it's been a few years. This method will require a little bit of hand calc on your part to derive a constant and an angle to plug in to excel, then excel should be able to apply the formula to every data point. An excel mastermind could probably figure out how to automate the whole thing, but I can only picture how to plug the fully derived formula in.

The actual theta and M values obviously only apply to the drawn example, but the below is how I'd begin. When I refer to "Real" it's your state plane coordinates, and data are obviously your data coordinates.

I'll write up a better explanation of what's happening tonight, and how to apply the formulas shown. Once you get the hang of it, it should be pretty smooth sailing if you do it all the time.

The whole idea here is rotating a coordinate axis. Like you said, there IS a mathematical relationship between the two. It's predictable, and conversions can be made.

In order to use this, a rule has to be followed. The way I derived it, I made it as simple as possible so a few terms and steps would drop out (being zero).

- The two points you use to find the angle must be on the x axis. The first point will always be the origin (0,0), and the next is a convenient point along the x-axis. (30,0) is used in the example.

tan^-1 is also known as arctan, or inverse tangent. It is a trig function that helps you find the angle we will be using in this particular case. Not to be confused with regular tan. A scientific calculator can help you here. To check to see if you are plugging the numbers in right, the inverse tangent of 2 should come out to be 63.435 degrees. If the number looks off, make sure your calculator is calculating in degrees instead of radians. Either degrees or radians will work, as long as they are used consistently. Many people find degrees more intuitive and familiar, so it is sometimes easier to stick with those.

For the m value, when you go to calculate something like 30cos(59.04), make sure you do cos(59.04) first, then multiply that by 30. Some calculators give real goofy answers if you do it like it is written.

Depending on the orientation of the grid to the state plan, both the angles and m values may occasionally come out negative. Make sure to preserve the sign in your calculations.

If you can understand that survey mumbo jumbo earlier in this thread, you can get this down no problem. I'd be happy to help you work through converting a real data set with numbers you use if you wanted. If you have the state plane coordinates of the data origin, and a point along the x axis, we can work through an example.

Link made my head hurt

Three dimensional trig solutions takes me back to multivariate calc. Days I'd rather forget.