Real estate surveys are a necessary step in any processes involving property. They can be arranged at the buying or selling of a home to square away particular details or they can be requested to clarify boundaries during border disputes. The point of a particular survey can change the details that it focuses on but having hard facts and measurements can mean the difference between a simple case and a complex one.
Properties, when you boil it down, refer to parcels of land more than, say, the actual house you are purchasing. A house is considered an improvement of the property just like a driveway or ground-level pool might be. As defined by the American Bar Association, a survey is a drawing of your property and shows any improvements on it. It includes the boundary lines as well as any encroachments affecting the property. Encroachments most often refer to third party or neighboring property assets like utility pipes or fences.
It may be useful to pay for a comprehensive survey if you think it will help in any property litigation ahead of you. Apart from that, lenders will often require a survey be obtained alongside a sale or closing as the survey is the only document that can confirm that the legal description of your deed matches the piece of property.
In short, the answer is a matter of clarity and protection. Real estate surveys can be a useful tool in solving property disputes and in transactions can be the authoritative review of a property to ensure that all details and improvements are kept accounted for.