Question: What is sea level barometric pressure and how is it different than absolute barometric pressure?
Answer: Sea level barometric pressure is barometric pressure measured at sea level. Absolute barometric pressure is barometric pressure measured at altitude.
Using sea level barometric pressure on an ABC watch is more effective, as it provides a consistent variable to compare to altitude. This is how the pressure / altitude tables are programmed into the watch.
In order to properly set your Core or other Suunto ABC watch, all you need to know is either sea level barometric pressure, or altitude. Once you enter in one of those, the watch will automatically be programmed for both sea level barometric pressure and altitude.
In order to get your sea level pressure, there are a number of resources online to get this information. Here is one place:
Note: If you set your Core at a known altitude, and you find you are a few millibars off in terms of sea level barometric pressure from the latest weather report at your regional airport, etc. that is normal. It is normal to see minor fluctuations in barometric pressure over a small region (i.e., 10 square miles).
Note: You cannot manually calibrate the watch sensor on the Core. You can however, manually calibrate the watch sensor on Vectors, X-landers, and Observers.