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## Descriptive Geometry Eng. Areej Afeefy

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**Descriptive GeometryEng. AreejAfeefy**Ref. Descriptive Geometry Metric PARE/LOVING/HILL Fifth edition**Descriptive Geometry**• Descriptive Geometry: is the science of graphic representation and solution and space problems By Arch. Areej Afeefy**projections**• Two common types of projections: 1) perspective projections (used by architects or artists) 2) orthographic projections (perpendicular to the object)**Perspective Projection**Screen Human eye**Orthographic Projection**Screen**Orthographic Projection**Horizontal Front Profil**Horizontal**Profil Front**Steps to obtain a view**• Establish the line of sight. • Introduce the folding line • Transfer distances to the new view • Determine visibility and complete the view**Step 1: Establish the line of sight.**Primary Auxiliary Views Step 2: Introduce the folding line Step 3: transfer distances a,e d,h y b,f c,g H 1 Step 4: determine visibility and complete view D2 1 D1 D y h d g k1 e D2 c y f a D1 f,e g,h b b,a c,d**All views projected from top view has the same height**dimension**All the views projected from front view have the same depth**dimension**the true angel between a line and any projection plane**appears in any view shows the line in true length and the projection plane in Edge View.**Bearing , Slope, and Grade**N N aH aH S55oE 55 b b Bearing: a term used to describe the direction of a line on the earth’s surface**Azimuth Bearing**N aH aH 125o N125o b b**problem**• A 160-m segment AB of a power line has a bearing of N 60o and a downward slope of 20o from the given point A. Complete the front and top views. ah aF**D1**D1 D1 D1 b 1 20o H 160 m N b N 60o a1 ah H F aF b**Grade**Grade: another way to describe the inclination of a line from the horizontal Plane**Chapter 4**Planes