Department of Construction Management & Civil Engineering Technology ‐ NYCCTCMCE-1110 Construction Engineering Drawings 1

Lecture #6 Orthographic Projection

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Orthographic Projection

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What it is?It is the means of representing a three dimensional object in two dimensions. It uses multiple views of the object, from points of view rotated about the center through increments of 90 degrees.

Visualize the surface of the object being projected onto the sides (planes) of a transparent box that is around the object.

Orthographic Projection

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Orthographic Projection is a way of drawing an object from different directions. Usually a front,side and plan view are drawn so that a person looking at the drawing can see all the importantsides. Orthographic drawings are useful especially when a design has been developed to a stagewhereby it is almost ready to manufacture. There are two ways of drawing in orthographic - FirstAngle and Third Angle. They differ only in the position of the plan, front and side views. Below isan example of first angle projection.

Above is a simple L-shape, drawn in three dimensions. Below is the same shape drawn inorthographic projection. This orthographic projection appears to have three separate drawings butthey are the same L-shape. The first drawing is the front view (drawn looking straight at the frontof the L-shape), the second is a drawing of the L-shape seen from the side and last of all a drawingfrom above known as a plan view

Orthographic Projection

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Imagine standing directly in front of the L-shape. You would only see the front edges, not the sides

THE FRONT VIEW THE SIDE VIEW

Now imagine standing directly at the side of the L-shape, the drawing opposite shows exactly what you would see

Orthographic Projection

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Purpose:Orthographic Projection is used in drawing as often as your scale will be used.As all drawings are considered scaled drawings so too are those drawings considered to be employing orthographicprojection techniques. It is a method that allows you to visually communicate a 3 dimensional object onto a 2dimensional drawing surface. Primarily, it will help you understand how to extrude or project an objects surfaceswithout measuring them (IE…accurately draw the documents for a building off a photograph, etc…)

Multiple Views without RotationAn object is viewed through a plane projecting from a point at infinity to obtain an accurate outlineThe projection of one face of an object is not sufficient enough to provide a comprehensive outline of the entireobject. To do this, an objects sides are projected onto the PRINCIPLE PLANES of a transparent imaginary boxthat encompasses the object and are:

•VERTICAL•HORIZONTAL•PROFILE

This will allow the objects true length, width & height to be accurately represented on the drawing plane and in theproper relationship to the other drawing planesThe Angles formed between the horizontal & vertical planes are called the:

•FIRST ANGLE•SECOND ANGLE•THIRD ANGLE•FOURTH ANGLE

These angles are used to project the side of the object perpendicular to its angle on its opposing Principle plane inintervals of Right Angles

Orthographic Projection Assignment Metal Bender

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¾”

½”

2”

1”3 ½”

1 ½” 1 ½”

1” Drill½” Radius

3/4” Drill 3/8”Radius

Hidden Line for ¾” radius

Orthographic Projection Assignment Kitchen Elevation

7Elevation A /NTS

2’-0”5’-0”1’-6”

1’-3” 2’-6” 1’-3”

1’-0” 1’-0”

UpperCabinets

Lower Cabinets

UpperCabinets

Lower Cabinets

Floor Plan /NTS

stove

Sample of a Cabinet Elevation & Section

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