A surveyor will mark your property lines. That will assure you know where they are, and you will also be able to see if there are any encroachment on the property, or if any part of your structure, fence, driveway, ect. encroaches on a neighboring property. Also, if you are getting title insurance, the new survey will be provided to the title insurance company, which will insure you there will be no problems arise in the future that the title insurance company would not be responsible for. Hope this answers your question.