A boundary survey is the surveyor's professional opinion on the location of property lines and corners of the subject land. The surveyor verifies the property corners to the recorded legal descriptions for the subject property as well as legal descriptions for adjacent properties and plats, the monuments set in the field, and any structures indicating lines of possession like fences, walls, hedges, and yards. The verification includes the research of both public and private data from a variety of sources such as public records, title companies, railroads, along with other professional entities. The surveyor will locate any encroachments onto or from the subject property and will reset any missing monuments. Typically the survey involves the setting or restoration of monuments or markers at the corners or along the lines of the parcel, often in the form of iron pipes, or concrete monuments in the ground or spikes, lead and tacks or well monuments set in concrete or asphalt. A map, or "Record of Survey", is then prepared in conformance with the Professional Land Surveyor Act and filed with the appropriate county Surveyor's Office and becomes public record.