Must the unit map of rural cadastral surveying and mapping be calculated according to the whole map?

When the land area is small and irregular, it is divided into several triangles, and the area of each connected triangle is calculated by Helen formula, and then added.

The accurate measurement of a large area of land is divided into small areas, measured block by block, and then added up.

The rough survey of large-scale land is to draw a map first and then measure it on the map.

The land survey area of the Bureau of Land and Resources and the Planning Bureau is an acre of land = 666.667 square meters, which is calculated by taking the theodolite located by GPS. The area of land is generally measured in mu, and the commonly used method is measurement. Measure the length and width of this land with a tape measure, and finally make the length (m) * width (m) * 0.00 15 = mu. For example, the land area with a length of 200m and a width of 150m is 200 (m) × 150 (m) × 0.00655.

There is a more practical formula to calculate: square meters are converted into acres, and the formula is "add half to the left and move three"