I was frustrated with small calibration targets that required measurement of 10-40 mm. My thought that was stepper error would be compounded over longer lengths. So I created a 120 mm target. The minor axis is 15mm. The thickness is 3mm. Perhaps someone has done this already...and I'm happy to give credit where credit is due.
Print and measure while still attached to the bed to avoid distortion from extraction.
Traditionally, all other things being equal, on smaller calibrations, say for a 10, 20, or 40 mm theoretical measurement, a +1% error would result in actual measurements of 10.1, 20.2, or 40.4 mm, whereas this print would provide a measurement of 121.2 mm. I don't know about you, but discerning an error of 1.2 mm is a lot easier than one that is 400 microns, especially when you factor in the anisotropic thermal distortions in the extruded part. Compared to the 40 mm calibration your sensitivity goes up by a factor of three.
Other thoughts and perspectives much appreciated.