Photogrammetric mapping may be developed from aerial photographs and is particularly useful for showing land contours, site conditions and details for large areas.
Electronic distance measuring equipment using light beams coupled with theodolites, enable the surveyor to measure precise angles and distances with greater ease and accuracy.
Sophisticated electronic equipment using orbiting satellites to determine both horizontal and vertical placement on the face of the earth is a relatively new innovation.
Surveying with a magnetic compass and surveyor’s chain was the method employed in most of the original subdivisions of the Commonwealth. Today the technique is primarily used for reconnaissance surveys of large tracts.