The document discusses the history and evolution of the plane table and alidade surveying instruments. It describes four phases: 1) The original "plain table" from the 17th century which used intersection of lines to locate points plotted on paper; 2) In the 19th century, the instrument became known as the plane table, with the addition of a telescope to the alidade and ability to measure vertical angles; 3) Further developments in the 19th-20th centuries included adding a stadia rod and scale to convert slope distances to horizontal and vertical measurements; 4) The plane table was widely used for topographic mapping through the 19th century before being replaced by modern total stations.