I understand how to get the max drift but not sure how to figure out estimated groundspeed etc.
Is there someone with a simple method for diversions?
Groundspeed = Airspeed plus or minus Wind Component. If the Wind is behind you, or in front of you the Component equals the Wind Speed. Hopefully you drew this on your chart before you started
0-30 degrees use full WC
30-60 degrees use 2/3 WC
60-90 degrees use 1/3 WC
For simple distance/time measurement your thumb is 10nm from the end to the knuckle on a 1/500k chart:
Thats 6 minutes at 100kts
5 minutes at 120 Kts
7 minutes at 85kts