layout techniques
chapter nineteen
General
Some methods of layout have been used since the beginning of time and others have only recently been used because of newly-available technology. The look of surveying may have changed with the new instruments, but the layout methods used in the field still have their roots in history. Techniques that were used in ancient times are still used throughout the world today. Modern instruments and methods may be used on modern projects, but in many areas, old-world methods are still used to lay out build-ings, irrigation ditches, and roads. No matter the method, old or new, someone still remains responsible for the layout. Someone still has to make decisions on the best way to place stakes in the ground.
Using The 3/4/5
Since the days of the ancient builders of Greece and Egypt, the 3/4/5 relationship has been used on construction sites to establish or to check perpendicular lines. Today's field engineer follows in the footsteps of the ancient builders whenever this relationship is used. Field engineers in all types of construction--residential, commercial, industrial, etc.--find the 3/4/5 useful for quick checks to confirm that a true 90° angle has been established even when using the most precise surveying equipment. The carpenters on projects use this relationship constantly to square walls, and even to plumb walls. In construction, the 3/4/5 is probably the most used of all geometry principles.
The 3/4/5 is used every day for construction layout.
By using common geometric and trigonometric formulas, the fact that the 3/4/5 is a right angle can be proven. A mathematics text should be referenced for more information.
Multiples of the 3/4/5
To use other triangles similar to the 3/4/5, simply multiply each side by the same con-stant. Some examples are shown.