I. Application:
Generally based on the horizon, above the horizon is positive, below the horizon is negative;
"plus or MINUS zero" will appear in the representation of numbers and symbols plus absolute value stored in the computer;
"Positive and negative zeros" are commonly used in mathematics, such as: 1, 2, 3 ... (those without negative signs are positive numbers) -3, -7, ... (those with negative signs are negative numbers);
Numbers greater than zero are called positive numbers, for example, 6 is also recorded as +6, and numbers less than zero are called negative numbers, for example, -6.
"plus or minus zero" can be used not only in mathematics, but also in expenditure and income.
Second, pay attention to:
The facade of the building you see is the front facade, which belongs to the commercial part. It happens that the first floor elevation of the commercial part is 0.000, and the second floor elevation is 3.900. Then you look at the floor plan of the building and the elevation marked on the stairs of the house, and this problem appears. As for the absolute elevation of 0.000 in the general description, it is not important here. The important thing is whether there is a height difference between the two parts, or a designer's mistake, which needs you to solve.