It would be a perfect world if only everything fit right the first time, and that is one of the goals of having plans. Laying the foundation down in the wrong place or even the wrong dimensions will throw an entire project off. The plans will generally be accompanied by a survey report, and that will tell the supervisor exactly where to put the beginnings of the structure. This is useful for those who would rather get it done correctly the first time.
Many buildings today are built on slabs, so knowing where to put the plumbing that will be embedded in it is a good idea. Digging out the area will come first, so the people running the machines for that will need a guide. Many construction projects might look disorganized as they begin, but each stake in the ground is a marker for a specific purpose. It tells each person where they will begin and end their work when the foundation, basement or slab is going to be placed.
Getting the first steps in the correct placement might take a lot of measurements and adjustments, but a good start will ensure a project gets off with fewer mistakes. It can save time and money for those who are in charge of accounting for the money, and it will give workers a comprehensive overlook at what they are doing. While many of them might not need to read blueprints, most of them have a nodding acquaintance with them.
Once the foundation is in its proper place, building from the ground up can proceed. The tradesmen working on the rest of the building will be able to begin their work with the knowledge that everything is where it should be, so their job is simply to keep working with that tenet in mind.