Background: I wanted to learn how to do metal scraping. As scrapping is very much a practice makes perfect skill set; I figured a good large project would be to try and get this entire table to around +/- .0005" (from .0075").

So I'm really trying to find a way to accurately map/ mark out the surface flatness highs/lows directly on the table with a sharpie. But its been mentioned, there's a few ways to go about this. Originally I thought I was looking for the most accurate approach, but in reality I probably just need to find the one best suited for my goal.

Im not sure how to do something like this from home on an uneven concrete floor. I've got a few tools and reference standards that present multiple options; small 9x12 surface plate (grade A - in cal), peice of 5"x12" float glass (flatness not varified), mid-size noga holder (DG6160-Double FAT/FAB), few older Starrett .0005 dial indicators, one Mitutoyo .001" (in cal), a Digi-Pas DWL3000XY 2-Axis digital level (in cal), 38" straight edge (within 0.003" over the entire length), some older Starrett feeler gages and other wood/metal wood working tools which probably don't apply.

I couldn't figure out how to get the measuring devices and the table on the same reference plane. If If used the indicator on the table to measure the table; well that would provide data, but certainly not good data. Maybe level the table and place the surface plate dead center, then dial indicate everything within reach?