check out your municipality's web site. Often the tax maps are on line. Your site plan though usually is more similar to the survey as it shows location of structures, pools, fence etc. You can take a copy of the survey and use this to create a plot plan if you are planning on an addition or other improvements. I have found plot plans to be less exact and not stamped vs surveys. You could also take tax maps and sketch in your improvements but this will require you to take measurements etc. When in doubt, get a survey. My neighbor built a large patio for his hot tub on neighbor's property and had to rip it out.