The task of engineering survey is mainly reflected in two aspects: one
is to express the position and shape of various existing objects, as well as the
undulating shape of the ground, etc. with graphs or data to provide basis for survey
work, which is called survey or mapping; the other is to demarcate the position of
buildings, structures or other graphs on the drawings formed by planning, design and
management, etc. on site As the basis of construction, it is called surveying and setting
out.