I’m not sure what a proper log is, but I learned to always keep a deck log for navigational purposes. On our current boat you can open any one of our log books and see the following: position at every hour of the day on the hour, who was on watch, water temp, air temp, course and speed, engine rpm, barometric pressure, true wind speed and direction as well as current speed/ direction , wave height direction and period. We also include observations such as shaft temps, generator temps, hydraulic oil temps engine room temps, alternator temps, radar targets, course and speed of targets, Important radio comms, fuel consumed, distance travelled and any unusual observations during the hour on watch. Notes for the next watch stander such as fuel tank switching for reballasting or watermaker starting or stopping any planned and unplanned course changes notes to fix anything that breaks etc...Takes at most 5 mins to record but what else have you to do on watch at 0300. Back in the days before gps this was all standard operating procedure. When you bought a well seasoned boat these logs were available and more often than not they added value for both the seller and the purchaser. Each log covers a little more than 950 hours of run time so we use one of the 6 radio log pages for maintenance items as well. Now there are actually companies making equipment to automatically record this kind of data so I guess it must be useful and even worth paying for.