One common way to do this is by printing a model with 50-100 layers and then only measuring the top 20 or so layers. So before you spend too much time trying to perfect the dimensional accuracy of your prints, you need to verify that your measurements are not being affected by the first layer position.
Future layers can also be affected by the extra plastic on this layer, which creates several oversized layers at the bottom of the part. For example, if you are printing a 0.2mm thick layer, but your nozzle is only positioned 0.1mm away from the bed, then this extra plastic may create a first layer that is a bit too large.
If your nozzle is too high or too low for the first layer of your print, it can drastically affect the next 10-20 layers of the part. Settings for your first layer can have an impact on dimensional accuracy.
