Excellent work as always. Your illustrations really help with understanding. We always appreciate it when you have both metric and imperial measurements. I noticed that you used the Euro date format though: 10/06/1999. In the U.S., we usually read this as October 6, 1999 rather than June 10, 1999 as intended. Since there are mixed audiences, you may wish to spell out the month (10 Jun 1999 for example). You could use ISO 8601, but that's not always obvious to those who aren't familiar, so spelling out the month may be best. Nice work!
