Scaling Problem

It is hard for me to describe my problem, but here is my best shot.......

I work in construciton management and work with both architects and surveyors. I have a drawing that was drawn in decimal unitless units that was created by my surveying company. I want to overlay the surveying drawing over the architectural general arrangement. However when I change the units from decmial to architectual or architectural to decimal the coordinate systems are thrown off and the measurements change. I don't undersand why. If I draw a line 162 units long in decimal and then convert to architectural I would expect the line to read 162'. Instead it read 13'6". CAD assumes I was drawing in inches. This is not the case. Is there a way to change back and forth from decimal to architectural without scaling the drawing up or down and keeping the same coordinate system?

Using Architectural units, a drawing unit is 1 inch... 13'-6"=162". You'll need to scale by a factor of 12.

The problem is I have a coordinate system set up for the surveying drawing. If I convert to architectural and then scale it by a factor of 12, I have thrown off the coordinates of my building corners and all my turning points.

The problem is I have a coordinate system set up for the surveying drawing. If I convert to architectural and then scale it by a factor of 12, I have thrown off the coordinates of my building corners and all my turning points.

If the model is too small then the coordinates must be wrong now anyway.

Reverse the process. You obviously want to stay with your survey units. Pull the architectural general arrangement into your survey drawing.