Orthographic Projections of Points & Lines - Engineering Graphics and Design (BTME-101-21)

Oct 28, 2026

Engineering Graphics and Design BTME-101-21 explains orthographic projections using the HP and VP reference planes with an X–Y line. It covers the meaning of “above/below” relative to H.P. and “in front/behind” relative to V.P., and how objects are located across the four quadrants to predict the effects on views FV and TV. The document sets notation rules for naming points, lines, and views, then applies the method to specific cases for a point and outlines line projection cases (vertical, parallel to planes, and various inclinations) with pictorial and orthographic patterns.

LanguageEnglish

CategoryExam

FormatPDF

Pages23

Reading Time58 min

AccessFree to download

Orthographic Projections of Points & Lines

Terms: above/below and in front/behind

Notations for naming views (FV, TV, VP, HP)

Projections of a point in different quadrants

Pictorial and orthographic presentations for points

Projections of straight lines and their cases

|
ORTHOGRAPHIC PROJECTIONS
OF POINTS & LINES | | --- | | Engineering Graphics and Design
(BTME-101-21) | | | | ORTHOGRAPHIC PROJECTIONS
OF POINTS, LINES, PLANES, AND SOLIDS. | | | | --- | --- | --- | --- | --- | | | | | | | | | TERMS ‘ABOVE’ & ‘BELOW’ WITH RESPECTIVE TO H.P. | | | | | | AND TERMS ‘INFRONT’ & ‘BEHIND’WITH RESPECTIVE TO V.P
FORM 4 QUADRANTS. | | | | | | OBJECTS CAN BE PLACED IN ANY ONE OF THESE 4 QUADRANTS. | | | | | | IT IS INTERESTING TO LEARN THE EFFECT ON THE POSITIONS OF VIEWS ( FV, TV ) OF THE OBJECT WITH RESP. TO X-Y LINE, WHEN PLACED IN DIFFERENT QUADRANTS. | | | | | 2 | | | |
2 | NOTATIONS FOLLOWING NOTATIONS SHOULD BE FOLLOWED WHILE NAMING DIFFERENT VIEWS IN ORTHOGRAPHIC PROJECTIONS. | OBJECT | POINT A | LINE AB | | --- | --- | --- | | IT’S TOP VIEW | a | a b | | IT’S FRONT VIEW | a’ | a’ b’ | | IT’S SIDE VIEW | a” | a” b” | SAME SYSTEM OF NOTATIONS SHOULD BE FOLLOWED INCASE NUMBERS, LIKE 1, 2, 3 – ARE USED. 3 3 |

X

Y

| | | | --- | --- | --- | | | 2nd Quad.
X
3rd Quad.

VP
Y

1ST Quad.

Observer
HP
4th Quad. | | | | | | | | | | | | | | |

THIS QUADRANT PATTERN,
IF OBSERVED ALONG X-Y LINE ( IN RED ARROW DIRECTION) WILL EXACTLY APPEAR AS SHOWN ON RIGHT SIDE AND HENCE, IT IS FURTHER USED TO UNDERSTAND ILLUSTRATION PROPERLLY. | | | | | | | | | | | | Point A is Placed Indifferent quadrantsand it’s Fv & Tv are brought in same plane for Observer to see
clearly.
Fv is visible as it is a view on VP. But as Tv isis a view on Hp, it is rotated
downward 900,
In clockwise direction.The In front part of Hp comes below xy line and the part behind Vp comes above.
Observe and note the process. | POINT A IN
2ND QUADRANT
A
HP

V Pa’

a
OBSERVER | | | | | |
POINT A IN 1ST QUADRANT
A

HP OBSERVER

| | | | | | | | | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | HP a a’ A

OBSERVER
POINT A IN
3 RD QUADRANT
VP | | | | | | HP a
a’
A

OBSERVER
POINT A IN
VP 4TH QUADRANT | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 5
5
| | | | | | | | | | | | | | | | PROJECTIONS OF A POINT IN FIRST QUADRANT.

POINT A ABOVE HP & INFRONT OF VP

POINT A ABOVE HP & IN VP

POINT A IN HP & INFRONT OF VP | | | | | --- | --- | --- | --- | | 6 | X

For Tv

A
PICTORIAL PRESENTATION

PICTORIAL PRESENTATION

Fv above xy, Tv below xy.
Y
X
VP
HP
a’
a

ORTHOGRAPHIC PRESENTATIONS OF ALL ABOVE CASES.

Fv above xy,

Tv on xy.
Y
X
VP
a’
a
HP
| X

| | | | | Fv on xy, Tv below xy.
Y
X
VP
a’
a
HP
|
6 | | | | PROJECTIONS OF STRAIGHT LINES. | | | --- | --- | --- | --- | | | INFORMATION REGARDING A LINE means
IT’S LENGTH,
POSITION OF IT’S ENDS WITH HP & VPIT’S INCLINATIONS WITH HP & VP WILL BE GIVEN.
AIM:-TO DRAW IT’S PROJECTIONS-MEANS FV & TV. | | | | SIMPLE CASES OF THE LINE
1. A VERTICAL LINE ( LINE PERPENDICULAR TO HP & // TO VP)
2. LINE PARALLEL TO BOTH HP & VP.
3. LINE INCLINED TO HP & PARALLEL TO VP.
4. LINE INCLINED TO VP & PARALLEL TO HP.
5. LINE INCLINED TO BOTH HP & VP.
STUDY ILLUSTRATIONS GIVEN ON NEXT PAGE SHOWING CLEARLY THE NATURE OF FV & TV OF LINES LISTED ABOVE AND NOTE RESULTS.
7
7
| | | | | (Pictorial Presentat

FAQs

How are “above/below” and “in front/behind” defined in orthographic projections?

“Above/below” is defined with respect to H.P., while “infront/behind” is defined with respect to V.P. The position of the object relative to these planes determines the view locations.

What notations should be followed when naming the different views of an object?

The document specifies a notation system for top view, front view, and side view using labels like a, a’, and a” for points, with corresponding line notations such as ab, a’b’, and a”b” for lines.

What are the main cases considered when projecting straight lines?

Straight lines are handled through simple cases such as a vertical line, lines parallel to both planes, lines inclined to one plane and parallel to the other, and lines inclined to both HP and VP, with pictorial and orthographic projection patterns.

Oct 28, 2026

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