In order to calculate the area of a land, the total area of land will be divided into different triangles. Then length of each side of the triangle will be measured. By using Herons Formula, the area of each triangle will be calculated. The sum of the area of all the triangles will be the total land area.
The Land Area Calculator app will help you in the land area calculation. You will have to select the input unit and enter all the lengths of 3 sides. The app will do the rest of calculation and give you the total area in different units.