A sample rate of 30 minutes apart if you are trying to measure area usage that would seem more appropriate. People that come in to do work rarely do less than that. My SWAG would be 90 minutes minimum time spent at DMS on average.
If goal is to sample how long people stay at DMS, then 10 minutes would be more reasonable to get an better assessment - but that assumes you are willing to track that person around.
RFID door rate will give you some idea of arrival (but this involves Personally Identifiable Information), but then there’s tailgating, walking up ramp when door open.
But no telling when they leave.
Also define “activity”, are two people sitting and talking an activity? Is it just BS’ing or it it a discussion about a project or a discussion about DMS? I was at DMS the other night, sitting with 2 other folks for over an hour. During that time, a third person came to collect a donation I promised for DMS (which is why I came), with the other two we discussed equipment status, new airline inline instillation, training, other “BS” items, answering several other members’ questions they came over to ask. I consider all of that “activity”, even the social part (which builds community cohesion).
I think what your doing is an interesting study and useful information. But before capturing the information, define how you will interpret it and what you want out as output. That will control the input.