Curious, what industry is this that you speak of? That may be an easy way to measure ride height for the shadetree mechanic like us or the local tire shop, and it may be "accurate enough" for our uses, but it is not accurate for the automotive industry if that is what you're referring to. There are too many variables in the forming and installation of a body panel to use it as a datum for vehicle height data. And if you are trying to compare this data to someone else's, you also have to consider the possibility of aftermarket panels, damage, repairs, and slight changes to the OEM panel shape over time. The method (that OEMs I'm familiar with) use to gather ride height data is measuring the height of the wheel center, then a datum on the chassis (often a suspension mount, such as LCA).
I have to point out that technically you haven't actually measured ride height either, you've only measured the distance from the fender lip to the wheel center. Doing this before/after is easy, (and useful to track ride height changes), but it only tells you the change in ride height, not the ride height.
Source: Career in automotive OEM design and QC; weight, height & alignment is one of my direct responsibilities.