# Technical Graphics - Projection Systems - Orthographic

At first Orthographic Projection can be difficult to understand, but we'll take it in small steps and you should have little or no trouble.

Let's take a very simple object such as a chair as our demonstration topic. Pretend you wanted a friend or a carpenter to make another chair the exact same, could you send them the picture on the right with a few measurements? This type of picture is called a Pictorial.

Well you could but the chances are that the chair would not be the exact same.

Your friend or carpenter will have a number of problems. What does the underside of the chair look like ? How much of a curvature is there on the backrest ? And there are many more. Wouldn't it be lovely if the person making the chair could see exactly what the chair looks like from the front or the side… the solution to these problems is Orthographic Projection.

Just look at all the different views Orthographic Projection can give us :
 Top Bottom Right side Left side Front Back
Did you know from the pictorial of the chair above that the seat was curved ?

And what about the lever underneath the seat !!!

Most objects are fairly simple and so you don't need all of the above Orthographic views to show someone how the object looks. Generally 3 views is enough and you won't be asked to use any more for a while yet.
Section 1 : This Lesson shows you the imaginary Glass Box and then goes onto First Angle Projection.

Section 2 : This Lesson shows Third Angle Projection.

Section 3 : This Lesson shows you how to determine wheather you are working in First or Third Angle Projection.

Section 4 : In this Lesson you get to put all of your newly acquired knowledge to the test with a wide variety of problems and question relating to Orthographic Projection.