ALTA/ACSM surveys are the most comprehensive survey you can get and are often required by lenders and title companies. Developed by the ALTA (American Land Title Association) and ACSM (American Congress on Surveying and Mapping) or NSPS (National Society of Professional Surveyors), they follow a set of minimum standards to promote uniformity and cover all aspects of a boundary survey, as well as identifying additional evidence of possession or improvement. Though expensive due to their extensive research and fieldwork, their thoroughness is essential for those acquiring properties.