This study aims to analyze Joseon mathematical knowledge and its application to real world. The mathematical knowledge refers to measuring the area of plane figures, known as square-shaped land(方田). Its application is land surveys(量田) conducted for taxation purposes. Specifically, this study analyzes the correlation between the related contents in representative mathematical books of the Joseon Dynasty, such as MuksaJipsanbub (17th century), Guiljib (18th century), and SanhakIbmun (18th century), and the shapes and areas of plane figures presented in GwangmuYangan (20th century). The analysis reveals both differences and similarities in the measured area between mathematical books and real world land surveys. While most results of the land survey align with the results obtained from mathematical methods, differences arise due to variations in real measurement of lengths and given conditions in the problems. Additionally, various aspects such as the focus on rectangles in land surveys, the proportionality and relativity of lengths, types of approximation, composed shapes, the purpose of problem solving, and reasoning of unspecified shapes or measures are discussed.