This advice is possibly of more practical help. GIMP (in the link below) is free software which can be used to make the reference points required to make the cross sections if you're working from a digital drawing. I found it very easy to use.

-Useful controls: Ctrl+Scroll wheel zooms in and out, Shift+M opens measuring tool, Units of measurement can be changed in bottom left corner of screen, the measuring points can be "grabbed and dragged"
-Click one point and drag to another point along a reference line such as known overall length or (even better) an incorporated scale in the drawing.
-Record this measurement and find the ratio of it to the known measurement.
-When measuring, two coordinates are given to the right of the total distance, the first is horizontal distance, the second is vertical distance. I used these coordinate measurements to plot out the cross sections. The software also gives you an angle and total distance if you prefer a protractor.

From there, it's a very straight forward process.

: Thanks Michael, yes I can tell the construction is straight forward. Not
: bragging but looks pretty simple to me. I build furniture so not concerned
: about the construction.