Surveying = to measure boundaries, area, or elevations of part of the earth's surface by means of measuring
    angles & distances.

Area Measurements:
    1 acre = 4,840 square yard or 43,560 square feet
    1 Township = 36 sq miles
    1 Section = 640 ac or 1 sq mile
    1 league (Spanish used in early TX & CA) =  4,428 acres = 3 sq miles = 3 sections
    1 labor (Spanish used in early TX & CA) = 200 acres
    1 arpent (French, used in early MO & LA) = .85 acres

Linear Measurements:
    1 chain = 100 links of iron or steel or about 20 meters or 66 feet
    1 pole = 1 rod = 1 perch = 5.5 yds = 16.5 ft = 5.03 meters
    1 vara (Spanish used in early TX & CA) = approx. 1 yard