In plane surveying, the distance between two points is defined as which distance?

• A. Vertical distance
• B. Horizontal distance
• C. Slope distance
• D. Direct distance

Answer: (B)

In plane surveying, measurements are taken on a horizontal plane, so the distance between two points is the horizontal distance—also called the planimetric distance—whose value comes from projecting the line joining the points onto the horizontal plane and ignoring any elevation difference. Vertical distance would reflect how high one point is above the other, which isn’t the distance used in a plane view. Slope distance is the true 3D length along the line, including vertical change, and direct distance can refer to that 3D straight-line distance as well. Thus the horizontal distance best fits the idea of distance in plane surveying.