What is difference between first angle and third angle projection?

Question

I getting bit confused here, at first I read that they both used the same elevations but organised them in different way. However some pictures I seened are not like this. I know it do with using different planes on opposite side to each other so wouldn't you just get different location of your elevations on the object e.g. in first angle you would get plan view of bottom but third you would get plan view of top.

Answer 1

In first angle projection, that object is assumed to be in the first quadrant. Hence, the top view is projected below, i.e. to the x-z plane - which lies below the object. Hence when all the three view are drawn, you will get the top view below the front view.

In the third angle projection, the object is assumed to be in the second quadrant. Hence when the entire drawing is finished, the top view remains on the top.

Generally, these differences do rarely come in the industry as the drawings need to be so detailed and meticulous that entire plan(top view) takes one sheet and the elevation(front view) takes another.