Depends on what you are measuring and how accurate you want to be. I do a lot of farms. Have you got an 840' tape? That is what you need to measure a dual breeder hen house with middle egg room. Actually, I count steel trusses in most steel truss barns in my region. They are 10' span 99% of the time. Otherwise, I trust the owner to tell me the truth. Most of these are built to exacting specs required by contract. Barns, corrals, arenas, etc. are easiest to measure by wheel in my experience, but they don't have bay windows, either. I use an appraisers tape with the special double hooks that hang on corners better to measure exterior on most dwellings, a sonic device for upper floor rooms, basements, etc. Warehouses, etc. I use assessor measurements, or company plans using my judgment and the wheel to check critical measurements. In college we were taught compass and pace techniques. My pace is still 5.4' (two steps = 1 pace), which conveniently is 10% less than 6'. I still pace long driveways, lots, lagoons, CLFing, etc.
Ter of the Ozarks
And it never hurts to add the caveat to the sketch about dimensions are estimates only and not intended for exact measurements.